---
layout: docs
page_title: Agents - Configuration File Reference
description: >-
  Use agent configuration files to assign attributes to agents and configure multiple agents at once. Learn about agent configuration file parameters and formatting with this reference page and sample code.
---

# Agents Configuration File Reference ((#configuration_files))

This topic describes the parameters for configuring Consul agents. For information about how to start Consul agents, refer to [Starting the Consul Agent](/consul/docs/agent#starting-the-consul-agent).

## Overview

You can create one or more files to configure the Consul agent on startup. We recommend
grouping similar configurations into separate files, such as ACL parameters, to make it
easier to manage configuration changes. Using external files may be easier than
configuring agents on the command-line when Consul is
being configured using a configuration management system.

The configuration files are formatted as HCL or JSON. JSON formatted configs are
easily readable and editable by both humans and computers. JSON formatted
configuration consists of a single JSON object with multiple configuration keys
specified within it.

<CodeTabs heading="Example Configuration File">

```hcl
datacenter = "east-aws"
data_dir = "/opt/consul"
log_level = "INFO"
node_name = "foobar"
server = true
watches = [
  {
    type = "checks"
    handler = "/usr/bin/health-check-handler.sh"
  }
]

telemetry {
  statsite_address = "127.0.0.1:2180"
}
```

```json
{
  "datacenter": "east-aws",
  "data_dir": "/opt/consul",
  "log_level": "INFO",
  "node_name": "foobar",
  "server": true,
  "watches": [
    {
      "type": "checks",
      "handler": "/usr/bin/health-check-handler.sh"
    }
  ],
  "telemetry": {
    "statsite_address": "127.0.0.1:2180"
  }
}
```

</CodeTabs>

### Time-to-live values

Consul uses the Go `time` package to parse all time-to-live (TTL) values used in Consul agent configuration files. Specify integer and float values as a string and include one or more of the following units of time:

- `ns`
- `us`
- `µs`
- `ms`
- `s`
- `m`
- `h`

Examples:

- `'300ms'`
- `'1.5h'`
- `'2h45m'`

Refer to the [formatting specification](https://golang.org/pkg/time/#ParseDuration) for additional information.

## General parameters

- `addresses` - This is a nested object that allows setting
  bind addresses. In Consul 1.0 and later these can be set to a space-separated list
  of addresses to bind to, or a [go-sockaddr] template that can potentially resolve to multiple addresses.

  `http`, `https` and `grpc` all support binding to a Unix domain socket. A
  socket can be specified in the form `unix:///path/to/socket`. A new domain
  socket will be created at the given path. If the specified file path already
  exists, Consul will attempt to clear the file and create the domain socket
  in its place. The permissions of the socket file are tunable via the
  [`unix_sockets` config construct](#unix_sockets).

  When running Consul agent commands against Unix socket interfaces, use the
  `-http-addr` argument to specify the path to the socket. You can also place
  the desired values in the `CONSUL_HTTP_ADDR` environment variable.

  For TCP addresses, the environment variable value should be an IP address
  _with the port_. For example: `10.0.0.1:8500` and not `10.0.0.1`. However,
  ports are set separately in the [`ports`](#ports) structure when
  defining them in a configuration file.

  The following keys are valid:

  - `dns` - The DNS server. Defaults to `client_addr`
  - `http` - The HTTP API. Defaults to `client_addr`
  - `https` - The HTTPS API. Defaults to `client_addr`
  - `grpc` - The gRPC API. Defaults to `client_addr`
  - `grpc_tls` - The gRPC API with TLS. Defaults to `client_addr`

- `alt_domain` Equivalent to the [`-alt-domain` command-line flag](/consul/docs/agent/config/cli-flags#_alt_domain)

- `audit` <EnterpriseAlert inline /> - Added in Consul 1.8, the audit object allow users to enable auditing
  and configure a sink and filters for their audit logs. For more information, review the [audit log tutorial](/consul/tutorials/datacenter-operations/audit-logging).

  <CodeTabs heading="Example audit configuration">

  ```hcl
  audit {
    enabled = true
    sink "My sink" {
      type   = "file"
      format = "json"
      path   = "data/audit/audit.json"
      delivery_guarantee = "best-effort"
      rotate_duration = "24h"
      rotate_max_files = 15
      rotate_bytes = 25165824
    }
  }
  ```

  ```json
  {
    "audit": {
      "enabled": true,
      "sink": {
        "My sink": {
          "type": "file",
          "format": "json",
          "path": "data/audit/audit.json",
          "delivery_guarantee": "best-effort",
          "rotate_duration": "24h",
          "rotate_max_files": 15,
          "rotate_bytes": 25165824
        }
      }
    }
  }
  ```

  </CodeTabs>

  The following sub-keys are available:

  - `enabled` - Controls whether Consul logs out each time a user
    performs an operation. ACLs must be enabled to use this feature. Defaults to `false`.

  - `sink` - This object provides configuration for the destination to which
    Consul will log auditing events. Sink is an object containing keys to sink objects, where the key is the name of the sink.

    - `type` - Type specifies what kind of sink this is.
      The following keys are valid:
      - `file` - Currently only file sinks are available, they take the following keys.
    - `format` - Format specifies what format the events will
      be emitted with.
      The following keys are valid:
      - `json` - Currently only json events are offered.
    - `path` - The directory and filename to write audit events to.
    - `delivery_guarantee` - Specifies
      the rules governing how audit events are written.
      The following keys are valid:
      - `best-effort` - Consul only supports `best-effort` event delivery.
    - `mode` - The permissions to set on the audit log files.
    - `rotate_duration` - Specifies the
      interval by which the system rotates to a new log file. At least one of `rotate_duration` or `rotate_bytes`
      must be configured to enable audit logging.
    - `rotate_max_files` - Defines the
      limit that Consul should follow before it deletes old log files.
    - `rotate_bytes` - Specifies how large an
      individual log file can grow before Consul rotates to a new file. At least one of `rotate_bytes` or
      `rotate_duration` must be configured to enable audit logging.

- `autopilot` Added in Consul 0.8, this object allows a
  number of sub-keys to be set which can configure operator-friendly settings for
  Consul servers. When these keys are provided as configuration, they will only be
  respected on bootstrapping. If they are not provided, the defaults will be used.
  In order to change the value of these options after bootstrapping, you will need
  to use the [Consul Operator Autopilot](/consul/commands/operator/autopilot)
  command. For more information about Autopilot, review the [Autopilot tutorial](/consul/tutorials/datacenter-operations/autopilot-datacenter-operations).

  The following sub-keys are available:

  - `cleanup_dead_servers` - This controls the
    automatic removal of dead server nodes periodically and whenever a new server
    is added to the cluster. Defaults to `true`.

  - `last_contact_threshold` - Controls the
    maximum amount of time a server can go without contact from the leader before
    being considered unhealthy. Must be a duration value such as `10s`. Defaults
    to `200ms`.

  - `max_trailing_logs` - Controls the maximum number
    of log entries that a server can trail the leader by before being considered
    unhealthy. Defaults to 250.

  - `min_quorum` - Sets the minimum number of servers necessary
    in a cluster. Autopilot will stop pruning dead servers when this minimum is reached. There is no default.

  - `server_stabilization_time` - Controls
    the minimum amount of time a server must be stable in the 'healthy' state before
    being added to the cluster. Only takes effect if all servers are running Raft
    protocol version 3 or higher. Must be a duration value such as `30s`. Defaults
    to `10s`.

  - `redundancy_zone_tag` <EnterpriseAlert inline /> -
    This controls the [`node_meta`](#node_meta) key to use when Autopilot is separating
    servers into zones for redundancy. Only one server in each zone can be a voting
    member at one time. If left blank (the default), this feature will be disabled.

  - `disable_upgrade_migration` <EnterpriseAlert inline /> -
    If set to `true`, this setting will disable Autopilot's upgrade migration strategy
    in Consul Enterprise of waiting until enough newer-versioned servers have been
    added to the cluster before promoting any of them to voters. Defaults to `false`.

  - `upgrade_version_tag` <EnterpriseAlert inline /> -
    The node_meta tag to use for version info when performing upgrade migrations.
    If this is not set, the Consul version will be used.

- `auto_config` This object allows setting options for the `auto_config` feature.

  The following sub-keys are available:

  - `enabled` (Defaults to `false`) This option enables `auto_config` on a client
    agent. When starting up but before joining the cluster, the client agent will
    make an RPC to the configured server addresses to request configuration settings,
    such as its `agent` ACL token, TLS certificates, Gossip encryption key as well
    as other configuration settings. These configurations get merged in as defaults
    with any user-supplied configuration on the client agent able to override them.
    The initial RPC uses a JWT specified with either `intro_token`,
    `intro_token_file` or the `CONSUL_INTRO_TOKEN` environment variable to authorize
    the request. How the JWT token is verified is controlled by the `auto_config.authorizer`
    object available for use on Consul servers. Enabling this option also enables
    service mesh because it is vital for `auto_config`, more specifically the service mesh CA
    and certificates infrastructure.

    ~> **Warning:** Enabling `auto_config` conflicts with the [`auto_encrypt.tls`](#tls) feature.
    Only one option may be specified.

  - `intro_token` (Defaults to `""`) This specifies the JWT to use for the initial
    `auto_config` RPC to the Consul servers. This can be overridden with the
    `CONSUL_INTRO_TOKEN` environment variable

  - `intro_token_file` (Defaults to `""`) This specifies a file containing the JWT
    to use for the initial `auto_config` RPC to the Consul servers. This token
    from this file is only loaded if the `intro_token` configuration is unset as
    well as the `CONSUL_INTRO_TOKEN` environment variable

  - `server_addresses` (Defaults to `[]`) This specifies the addresses of servers in
    the local datacenter to use for the initial RPC. These addresses support
    [Cloud Auto-Joining](/consul/docs/agent/config/cli-flags#cloud-auto-joining) and can optionally include a port to
    use when making the outbound connection. If no port is provided, the `server_port`
    will be used.

  - `dns_sans` (Defaults to `[]`) This is a list of extra DNS SANs to request in the
    client agent's TLS certificate. The `localhost` DNS SAN is always requested.

  - `ip_sans` (Defaults to `[]`) This is a list of extra IP SANs to request in the
    client agent's TLS certificate. The `::1` and `127.0.0.1` IP SANs are always requested.

  - `authorization` This object controls how a Consul server will authorize `auto_config`
    requests and in particular how to verify the JWT intro token.

    - `enabled` (Defaults to `false`) This option enables `auto_config` authorization
      capabilities on the server.

    - `static` This object controls configuring the static authorizer setup in the Consul
      configuration file. Almost all sub-keys are identical to those provided by the [JWT
      Auth Method](/consul/docs/security/acl/auth-methods/jwt).

      - `jwt_validation_pub_keys` (Defaults to `[]`) A list of PEM-encoded public keys
        to use to authenticate signatures locally.

        Exactly one of `jwks_url` `jwt_validation_pub_keys`, or `oidc_discovery_url` is required.

      - `oidc_discovery_url` (Defaults to `""`) The OIDC Discovery URL, without any
        .well-known component (base path).

        Exactly one of `jwks_url` `jwt_validation_pub_keys`, or `oidc_discovery_url` is required.

      - `oidc_discovery_ca_cert` (Defaults to `""`) PEM encoded CA cert for use by the TLS
        client used to talk with the OIDC Discovery URL. NOTE: Every line must end
        with a newline (`\n`). If not set, system certificates are used.

      - `jwks_url` (Defaults to `""`) The JWKS URL to use to authenticate signatures.

        Exactly one of `jwks_url` `jwt_validation_pub_keys`, or `oidc_discovery_url` is required.

      - `jwks_ca_cert` (Defaults to `""`) PEM encoded CA cert for use by the TLS client
        used to talk with the JWKS URL. NOTE: Every line must end with a newline
        (`\n`). If not set, system certificates are used.

      - `claim_mappings` (Defaults to `(map[string]string)` Mappings of claims (key) that
        will be copied to a metadata field (value). Use this if the claim you are capturing
        is singular (such as an attribute).

        When mapped, the values can be any of a number, string, or boolean and will
        all be stringified when returned.

      - `list_claim_mappings` (Defaults to `(map[string]string)`) Mappings of claims (key)
        will be copied to a metadata field (value). Use this if the claim you are capturing
        is list-like (such as groups).

        When mapped, the values in each list can be any of a number, string, or
        boolean and will all be stringified when returned.

      - `jwt_supported_algs` (Defaults to `["RS256"]`) JWTSupportedAlgs is a list of
        supported signing algorithms.

      - `bound_audiences` (Defaults to `[]`) List of `aud` claims that are valid for
        login; any match is sufficient.

      - `bound_issuer` (Defaults to `""`) The value against which to match the `iss`
        claim in a JWT.

      - `expiration_leeway` (Defaults to `"0s"`) Duration of leeway when
        validating expiration of a token to account for clock skew. Defaults to 150s
        (2.5 minutes) if set to 0s and can be disabled if set to -1ns.

      - `not_before_leeway` (Defaults to `"0s"`) Duration of leeway when
        validating not before values of a token to account for clock skew. Defaults
        to 150s (2.5 minutes) if set to 0s and can be disabled if set to -1.

      - `clock_skew_leeway` (Defaults to `"0s"`) Duration of leeway when
        validating all claims to account for clock skew. Defaults to 60s (1 minute)
        if set to 0s and can be disabled if set to -1ns.

      - `claim_assertions` (Defaults to `[]`) List of assertions about the mapped
        claims required to authorize the incoming RPC request. The syntax uses
        [github.com/hashicorp/go-bexpr](https://github.com/hashicorp/go-bexpr) which is shared with the
        [API filtering feature](/consul/api-docs/features/filtering). For example, the following
        configurations when combined will ensure that the JWT `sub` matches the node
        name requested by the client.

        <CodeTabs heading="Ensure that the JWT sub matches the node name requested by the client">

        ```hcl
        claim_mappings {
          sub = "node_name"
        }
        claim_assertions = [
          "value.node_name == \"${node}\""
        ]
        ```

        ```json
        {
          "claim_mappings": {
            "sub": "node_name"
          },
          "claim_assertions": ["value.node_name == \"${node}\""]
        }
        ```

        </CodeTabs>

        The assertions are lightly templated using [HIL syntax](https://github.com/hashicorp/hil)
        to interpolate some values from the RPC request. The list of variables that can be interpolated
        are:

        - `node` - The node name the client agent is requesting.

        - `segment` <EnterpriseAlert inline /> - The network segment name the client is requesting.

        - `partition` <EnterpriseAlert inline /> - The admin partition name the client is requesting.

- `auto_reload_config` Equivalent to the [`-auto-reload-config` command-line flag](/consul/docs/agent/config/cli-flags#_auto_reload_config).

- `bind_addr` Equivalent to the [`-bind` command-line flag](/consul/docs/agent/config/cli-flags#_bind).

  This parameter can be set to a go-sockaddr template that resolves to a single
  address. Special characters such as backslashes `\` or double quotes `"`
  within a double quoted string value must be escaped with a backslash `\`.
  Some example templates:

  <CodeTabs>

  ```hcl
  bind_addr = "{{ GetPrivateInterfaces | include \"network\" \"10.0.0.0/8\" | attr \"address\" }}"
  ```

  ```json
  {
    "bind_addr": "{{ GetPrivateInterfaces | include \"network\" \"10.0.0.0/8\" | attr \"address\" }}"
  }
  ```

  </CodeTabs>

- `cache` configuration for client agents. The configurable values are the following:

  - `entry_fetch_max_burst` The size of the token bucket used to recharge the rate-limit per
    cache entry. The default value is 2 and means that when cache has not been updated
    for a long time, 2 successive queries can be made as long as the rate-limit is not
    reached.

  - `entry_fetch_rate` configures the rate-limit at which the cache may refresh a single
    entry. On a cluster with many changes/s, watching changes in the cache might put high
    pressure on the servers. This ensures the number of requests for a single cache entry
    will never go beyond this limit, even when a given service changes every 1/100s.
    Since this is a per cache entry limit, having a highly unstable service will only rate
    limit the watched on this service, but not the other services/entries.
    The value is strictly positive, expressed in queries per second as a float,
    1 means 1 query per second, 0.1 mean 1 request every 10s maximum.
    The default value is "No limit" and should be tuned on large
    clusters to avoid performing too many RPCs on entries changing a lot.

- `check_update_interval` ((#check_update_interval))
  This interval controls how often check output from checks in a steady state is
  synchronized with the server. By default, this is set to 5 minutes ("5m"). Many
  checks which are in a steady state produce slightly different output per run (timestamps,
  etc) which cause constant writes. This configuration allows deferring the sync
  of check output for a given interval to reduce write pressure. If a check ever
  changes state, the new state and associated output is synchronized immediately.
  To disable this behavior, set the value to "0s".

- `client_addr` Equivalent to the [`-client` command-line flag](/consul/docs/agent/config/cli-flags#_client).

- `config_entries` This object allows setting options for centralized config entries.

  The following sub-keys are available:

  - `bootstrap` ((#config_entries_bootstrap))
    This is a list of inlined config entries to insert into the state store when
    the Consul server gains leadership. This option is only applicable to server
    nodes. Each bootstrap entry will be created only if it does not exist. When reloading,
    any new entries that have been added to the configuration will be processed.
    See the [configuration entry docs](/consul/docs/agent/config-entries) for more
    details about the contents of each entry.

- `datacenter` Equivalent to the [`-datacenter` command-line flag](/consul/docs/agent/config/cli-flags#_datacenter).

- `data_dir` Equivalent to the [`-data-dir` command-line flag](/consul/docs/agent/config/cli-flags#_data_dir).

- `disable_anonymous_signature` Disables providing an anonymous
  signature for de-duplication with the update check. See [`disable_update_check`](#disable_update_check).

- `disable_http_unprintable_char_filter` Defaults to false. Consul 1.0.3 fixed a potential security vulnerability where malicious users could craft KV keys with unprintable chars that would confuse operators using the CLI or UI into taking wrong actions. Users who had data written in older versions of Consul that did not have this restriction will be unable to delete those values by default in 1.0.3 or later. This setting enables those users to **temporarily** disable the filter such that delete operations can work on those keys again to get back to a healthy state. It is strongly recommended that this filter is not disabled permanently as it exposes the original security vulnerability.

- `disable_remote_exec` Disables support for remote execution. When set to true, the agent will ignore
  any incoming remote exec requests. In versions of Consul prior to 0.8, this defaulted
  to false. In Consul 0.8 the default was changed to true, to make remote exec opt-in
  instead of opt-out.

- `disable_update_check` Disables automatic checking for security bulletins and new version releases. This is disabled in Consul Enterprise.

- `discard_check_output` Discards the output of health checks before storing them. This reduces the number of writes to the Consul raft log in environments where health checks have volatile output like timestamps, process ids, ...

- `discovery_max_stale` - Enables stale requests for all service discovery HTTP endpoints. This is
  equivalent to the [`max_stale`](#max_stale) configuration for DNS requests. If this value is zero (default), all service discovery HTTP endpoints are forwarded to the leader. If this value is greater than zero, any Consul server can handle the service discovery request. If a Consul server is behind the leader by more than `discovery_max_stale`, the query will be re-evaluated on the leader to get more up-to-date results. Consul agents also add a new `X-Consul-Effective-Consistency` response header which indicates if the agent did a stale read. `discover-max-stale` was introduced in Consul 1.0.7 as a way for Consul operators to force stale requests from clients at the agent level, and defaults to zero which matches default consistency behavior in earlier Consul versions.

- `enable_agent_tls_for_checks` When set, uses a subset of the agent's TLS configuration (`key_file`,
  `cert_file`, `ca_file`, `ca_path`, and `server_name`) to set up the client for HTTP or gRPC health checks. This allows services requiring 2-way TLS to be checked using the agent's credentials. This was added in Consul 1.0.1 and defaults to false.

- `enable_central_service_config` When set, the Consul agent will look for any
  [centralized service configuration](/consul/docs/agent/config-entries)
  that match a registering service instance. If it finds any, the agent will merge the centralized defaults with the service instance configuration. This allows for things like service protocol or proxy configuration to be defined centrally and inherited by any affected service registrations.
  This defaults to `false` in versions of Consul prior to 1.9.0, and defaults to `true` in Consul 1.9.0 and later.

- `enable_debug` When set, enables some additional debugging features. Currently, this is only used to
  access runtime profiling HTTP endpoints, which are available with an `operator:read` ACL regardless of the value of `enable_debug`.

- `enable_script_checks` Equivalent to the [`-enable-script-checks` command-line flag](/consul/docs/agent/config/cli-flags#_enable_script_checks).

  ACLs must be enabled for agents and the `enable_script_checks` option must be set to `true` to enable script checks in Consul 0.9.0 and later. See [Registering and Querying Node Information](/consul/docs/security/acl/acl-rules#registering-and-querying-node-information) for related information.

  ~> **Security Warning:** Enabling script checks in some configurations may introduce a known remote execution vulnerability targeted by malware. We strongly recommend `enable_local_script_checks` instead. Refer to the following article for additional guidance: [_Protecting Consul from RCE Risk in Specific Configurations_](https://www.hashicorp.com/blog/protecting-consul-from-rce-risk-in-specific-configurations)
  for more details.

- `enable_local_script_checks` Equivalent to the [`-enable-local-script-checks` command-line flag](/consul/docs/agent/config/cli-flags#_enable_local_script_checks).

- `disable_keyring_file` - Equivalent to the
  [`-disable-keyring-file` command-line flag](/consul/docs/agent/config/cli-flags#_disable_keyring_file).

- `disable_coordinates` - Disables sending of [network coordinates](/consul/docs/architecture/coordinates).
  When network coordinates are disabled the `near` query param will not work to sort the nodes,
  and the [`consul rtt`](/consul/commands/rtt) command will not be able to provide round trip time between nodes.

- `http_config` This object allows setting options for the HTTP API and UI.

  The following sub-keys are available:

  - `block_endpoints`
    This object is a list of HTTP API endpoint prefixes to block on the agent, and
    defaults to an empty list, meaning all endpoints are enabled. Any endpoint that
    has a common prefix with one of the entries on this list will be blocked and
    will return a 403 response code when accessed. For example, to block all of the
    V1 ACL endpoints, set this to `["/v1/acl"]`, which will block `/v1/acl/create`,
    `/v1/acl/update`, and the other ACL endpoints that begin with `/v1/acl`. This
    only works with API endpoints, not `/ui` or `/debug`, those must be disabled
    with their respective configuration options. Any CLI commands that use disabled
    endpoints will no longer function as well. For more general access control, Consul's
    [ACL system](/consul/tutorials/security/access-control-setup-production)
    should be used, but this option is useful for removing access to HTTP API endpoints
    completely, or on specific agents. This is available in Consul 0.9.0 and later.

  - `response_headers` This object allows adding headers to the HTTP API and UI responses. For example, the following config can be used to enable [CORS](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing) on the HTTP API endpoints:

    <CodeTabs heading="Enable CORS on the HTTP API endpoints">

    ```hcl
    http_config {
      response_headers {
        Access-Control-Allow-Origin = "*"
      }
    }
    ```

    ```json
    {
      "http_config": {
        "response_headers": {
          "Access-Control-Allow-Origin": "*"
        }
      }
    }
    ```

    </CodeTabs>

  - `allow_write_http_from` This object is a list of networks in CIDR notation (eg "127.0.0.0/8") that are allowed to call the agent write endpoints. It defaults to an empty list, which means all networks are allowed. This is used to make the agent read-only, except for select ip ranges. - To block write calls from anywhere, use `[ "255.255.255.255/32" ]`. - To only allow write calls from localhost, use `[ "127.0.0.0/8" ]` - To only allow specific IPs, use `[ "10.0.0.1/32", "10.0.0.2/32" ]`

  - `use_cache` ((#http_config_use_cache)) Defaults to true. If disabled, the agent won't be using [agent caching](/consul/api-docs/features/caching) to answer the request. Even when the url parameter is provided.

  - `max_header_bytes` This setting controls the maximum number of bytes the consul http server will read parsing the request header's keys and values, including the request line. It does not limit the size of the request body. If zero, or negative, http.DefaultMaxHeaderBytes is used, which equates to 1 Megabyte.

- `leave_on_terminate` If enabled, when the agent receives a TERM signal, it will send a `Leave` message to the rest of the cluster and gracefully leave. The default behavior for this feature varies based on whether or not the agent is running as a client or a server (prior to Consul 0.7 the default value was unconditionally set to `false`). On agents in client-mode, this defaults to `true` and for agents in server-mode, this defaults to `false`.

- `license_path` <EnterpriseAlert inline /> This specifies the path to a file that contains the Consul Enterprise license. Alternatively the license may also be specified in either the `CONSUL_LICENSE` or `CONSUL_LICENSE_PATH` environment variables. See the [licensing documentation](/consul/docs/enterprise/license/overview) for more information about Consul Enterprise license management. Added in versions 1.10.0, 1.9.7 and 1.8.13. Prior to version 1.10.0 the value may be set for all agents to facilitate forwards compatibility with 1.10 but will only actually be used by client agents.

- `limits`: This block specifies various types of limits that the Consul server agent enforces.

  - `http_max_conns_per_client` - Configures a limit of how many concurrent TCP connections a single client IP address is allowed to open to the agent's HTTP(S) server. This affects the HTTP(S) servers in both client and server agents. Default value is `200`.
  - `https_handshake_timeout` - Configures the limit for how long the HTTPS server in both client and server agents will wait for a client to complete a TLS handshake. This should be kept conservative as it limits how many connections an unauthenticated attacker can open if `verify_incoming` is being using to authenticate clients (strongly recommended in production). Default value is `5s`.
  - `request_limits` - This object specifies configurations that limit the rate of RPC and gRPC requests on the Consul server. Limiting the rate of gRPC and RPC requests also limits HTTP requests to the Consul server.
    - `mode` - String value that specifies an action to take if the rate of requests exceeds the limit. You can specify the following values:
      - `permissive`: The server continues to allow requests and records an error in the logs.
      - `enforcing`: The server stops accepting requests and records an error in the logs.
      - `disabled`: Limits are not enforced or tracked. This is the default value for `mode`.
    - `read_rate` - Integer value that specifies the number of read requests per second. Default is `-1` which represents infinity.
    - `write_rate` - Integer value that specifies the number of write requests per second. Default is `-1` which represents infinity.
  - `rpc_handshake_timeout` - Configures the limit for how long servers will wait after a client TCP connection is established before they complete the connection handshake. When TLS is used, the same timeout applies to the TLS handshake separately from the initial protocol negotiation. All Consul clients should perform this immediately on establishing a new connection. This should be kept conservative as it limits how many connections an unauthenticated attacker can open if `verify_incoming` is being using to authenticate clients (strongly recommended in production). When `verify_incoming` is true on servers, this limits how long the connection socket and associated goroutines will be held open before the client successfully authenticates. Default value is `5s`.
  - `rpc_client_timeout` - Configures the limit for how long a client is allowed to read from an RPC connection. This is used to set an upper bound for calls to eventually terminate so that RPC connections are not held indefinitely. Blocking queries can override this timeout. Default is `60s`.
  - `rpc_max_conns_per_client` - Configures a limit of how many concurrent TCP connections a single source IP address is allowed to open to a single server. It affects both clients connections and other server connections. In general Consul clients multiplex many RPC calls over a single TCP connection so this can typically be kept low. It needs to be more than one though since servers open at least one additional connection for raft RPC, possibly more for WAN federation when using network areas, and snapshot requests from clients run over a separate TCP conn. A reasonably low limit significantly reduces the ability of an unauthenticated attacker to consume unbounded resources by holding open many connections. You may need to increase this if WAN federated servers connect via proxies or NAT gateways or similar causing many legitimate connections from a single source IP. Default value is `100` which is designed to be extremely conservative to limit issues with certain deployment patterns. Most deployments can probably reduce this safely. 100 connections on modern server hardware should not cause a significant impact on resource usage from an unauthenticated attacker though.
  - `rpc_rate` - Configures the RPC rate limiter on Consul _clients_ by setting the maximum request rate that this agent is allowed to make for RPC requests to Consul servers, in requests per second. Defaults to infinite, which disables rate limiting.
  - `rpc_max_burst` - The size of the token bucket used to recharge the RPC rate limiter on Consul _clients_. Defaults to 1000 tokens, and each token is good for a single RPC call to a Consul server. See https://en.wikipedia.org/wiki/Token_bucket for more details about how token bucket rate limiters operate.
  - `kv_max_value_size` - **(Advanced)** Configures the maximum number of bytes for a kv request body to the [`/v1/kv`](/consul/api-docs/kv) endpoint. This limit defaults to [raft's](https://github.com/hashicorp/raft) suggested max size (512KB). **Note that tuning these improperly can cause Consul to fail in unexpected ways**, it may potentially affect leadership stability and prevent timely heartbeat signals by increasing RPC IO duration. This option affects the txn endpoint too, but Consul 1.7.2 introduced `txn_max_req_len` which is the preferred way to set the limit for the txn endpoint. If both limits are set, the higher one takes precedence.
  - `txn_max_req_len` - **(Advanced)** Configures the maximum number of bytes for a transaction request body to the [`/v1/txn`](/consul/api-docs/txn) endpoint. This limit defaults to [raft's](https://github.com/hashicorp/raft) suggested max size (512KB). **Note that tuning these improperly can cause Consul to fail in unexpected ways**, it may potentially affect leadership stability and prevent timely heartbeat signals by increasing RPC IO duration.

- `default_query_time` Equivalent to the [`-default-query-time` command-line flag](/consul/docs/agent/config/cli-flags#_default_query_time).

- `max_query_time` Equivalent to the [`-max-query-time` command-line flag](/consul/docs/agent/config/cli-flags#_max_query_time).

- `peering` This object allows setting options for cluster peering.

  The following sub-keys are available:

  - `enabled` ((#peering_enabled)) (Defaults to `true`) Controls whether cluster peering is enabled.
    When disabled, the UI won't show peering, all peering APIs will return
    an error, any peerings stored in Consul already will be ignored (but they will not be deleted),
    and all peering connections from other clusters will be rejected. This was added in Consul 1.13.0.

- `partition` <EnterpriseAlert inline /> - This flag is used to set
  the name of the admin partition the agent belongs to. An agent can only join
  and communicate with other agents within its admin partition. Review the
  [Admin Partitions documentation](/consul/docs/enterprise/admin-partitions) for more
  details. By default, this is an empty string, which is the `default` admin
  partition. This cannot be set on a server agent.

  ~> **Warning:** The `partition` option cannot be used either the
  [`segment`](#segment-2) option or [`-segment`](/consul/docs/agent/config/cli-flags#_segment) flag.

- `performance` Available in Consul 0.7 and later, this is a nested object that allows tuning the performance of different subsystems in Consul. See the [Server Performance](/consul/docs/install/performance) documentation for more details. The following parameters are available:

  - `leave_drain_time` - A duration that a server will dwell during a graceful leave in order to allow requests to be retried against other Consul servers. Under normal circumstances, this can prevent clients from experiencing "no leader" errors when performing a rolling update of the Consul servers. This was added in Consul 1.0. Must be a duration value such as 10s. Defaults to 5s.

  - `raft_multiplier` - An integer multiplier used by Consul servers to scale key Raft timing parameters. Omitting this value or setting it to 0 uses default timing described below. Lower values are used to tighten timing and increase sensitivity while higher values relax timings and reduce sensitivity. Tuning this affects the time it takes Consul to detect leader failures and to perform leader elections, at the expense of requiring more network and CPU resources for better performance.

    By default, Consul will use a lower-performance timing that's suitable
    for [minimal Consul servers](/consul/docs/install/performance#minimum), currently equivalent
    to setting this to a value of 5 (this default may be changed in future versions of Consul,
    depending if the target minimum server profile changes). Setting this to a value of 1 will
    configure Raft to its highest-performance mode, equivalent to the default timing of Consul
    prior to 0.7, and is recommended for [production Consul servers](/consul/docs/install/performance#production).

    See the note on [last contact](/consul/docs/install/performance#production-server-requirements) timing for more
    details on tuning this parameter. The maximum allowed value is 10.

  - `rpc_hold_timeout` - A duration that a client
    or server will retry internal RPC requests during leader elections. Under normal
    circumstances, this can prevent clients from experiencing "no leader" errors.
    This was added in Consul 1.0. Must be a duration value such as 10s. Defaults
    to 7s.

  - `grpc_keepalive_interval` - A duration that determines the frequency that Consul servers send keep-alive messages to inactive gRPC clients. Configure this setting to modify how quickly Consul detects and removes improperly closed xDS or peering connections. Default is `30s`.

  - `grpc_keepalive_timeout` - A duration that determines how long a Consul server waits for a reply to a keep-alive message. If the server does not receive a reply before the end of the duration, Consul flags the gRPC connection as unhealthy and forcibly removes it. Defaults to `20s`.

- `pid_file` Equivalent to the [`-pid-file` command line flag](/consul/docs/agent/config/cli-flags#_pid_file).

- `ports` This is a nested object that allows setting the bind ports for the following keys:

  - `dns` ((#dns_port)) - The DNS server, -1 to disable. Default 8600.
    TCP and UDP.
  - `http` ((#http_port)) - The HTTP API, -1 to disable. Default 8500.
    TCP only.
  - `https` ((#https_port)) - The HTTPS API, -1 to disable. Default -1
    (disabled). **We recommend using `8501`** for `https` by convention as some tooling
    will work automatically with this.
  - `grpc` ((#grpc_port)) - The gRPC API, -1 to disable. Default -1 (disabled).
    **We recommend using `8502` for `grpc`** as your conventional gRPC port number, as it allows some
    tools to work automatically. This parameter is set to `8502` by default when the agent runs
    in `-dev` mode. The `grpc` port only supports plaintext traffic starting in Consul 1.14.
    Refer to `grpc_tls` for more information on configuring a TLS-enabled port.
  - `grpc_tls` ((#grpc_tls_port)) - The gRPC API with TLS connections, -1 to disable. gRPC_TLS is enabled by default on port 8503 for Consul servers.
    **We recommend using `8503` for `grpc_tls`** as your conventional gRPC port number, as it allows some
    tools to work automatically. `grpc_tls` is always guaranteed to be encrypted. Both `grpc` and `grpc_tls`
    can be configured at the same time, but they may not utilize the same port number. This field was added in Consul 1.14.
  - `serf_lan` ((#serf_lan_port)) - The Serf LAN port. Default 8301. TCP
    and UDP. Equivalent to the [`-serf-lan-port` command line flag](/consul/docs/agent/config/cli-flags#_serf_lan_port).
  - `serf_wan` ((#serf_wan_port)) - The Serf WAN port. Default 8302.
    Equivalent to the [`-serf-wan-port` command line flag](/consul/docs/agent/config/cli-flags#_serf_wan_port). Set
    to -1 to disable. **Note**: this will disable WAN federation which is not recommended.
    Various catalog and WAN related endpoints will return errors or empty results.
    TCP and UDP.
  - `server` ((#server_rpc_port)) - Server RPC address. Default 8300. TCP
    only.
  - `sidecar_min_port` ((#sidecar_min_port)) - Inclusive minimum port number
    to use for automatically assigned [sidecar service registrations](/consul/docs/connect/proxies/deploy-sidecar-services).
    Default 21000. Set to `0` to disable automatic port assignment.
  - `sidecar_max_port` ((#sidecar_max_port)) - Inclusive maximum port number
    to use for automatically assigned [sidecar service registrations](/consul/docs/connect/proxies/deploy-sidecar-services).
    Default 21255. Set to `0` to disable automatic port assignment.
  - `expose_min_port` ((#expose_min_port)) - Inclusive minimum port number
    to use for automatically assigned [exposed check listeners](/consul/docs/connect/proxies/proxy-config-reference#expose-paths-configuration-reference).
    Default 21500. Set to `0` to disable automatic port assignment.
  - `expose_max_port` ((#expose_max_port)) - Inclusive maximum port number
    to use for automatically assigned [exposed check listeners](/consul/docs/connect/proxies/proxy-config-reference#expose-paths-configuration-reference).
    Default 21755. Set to `0` to disable automatic port assignment.

- `primary_datacenter` - This designates the datacenter
  which is authoritative for ACL information, intentions and is the root Certificate
  Authority for service mesh. It must be provided to enable ACLs. All servers and datacenters
  must agree on the primary datacenter. Setting it on the servers is all you need
  for cluster-level enforcement, but for the APIs to forward properly from the clients,
  it must be set on them too. In Consul 0.8 and later, this also enables agent-level
  enforcement of ACLs.

- `primary_gateways` Equivalent to the [`-primary-gateway`
  command-line flag](/consul/docs/agent/config/cli-flags#_primary_gateway). Takes a list of addresses to use as the
  mesh gateways for the primary datacenter when authoritative replicated catalog
  data is not present. Discovery happens every [`primary_gateways_interval`](#primary_gateways_interval)
  until at least one primary mesh gateway is discovered. This was added in Consul
  1.8.0.

- `primary_gateways_interval` Time to wait
  between [`primary_gateways`](#primary_gateways) discovery attempts. Defaults to
  30s. This was added in Consul 1.8.0.

- `protocol` ((#protocol)) Equivalent to the [`-protocol` command-line
  flag](/consul/docs/agent/config/cli-flags#_protocol).

- `reap` This controls Consul's automatic reaping of child processes,
  which is useful if Consul is running as PID 1 in a Docker container. If this isn't
  specified, then Consul will automatically reap child processes if it detects it
  is running as PID 1. If this is set to true or false, then it controls reaping
  regardless of Consul's PID (forces reaping on or off, respectively). This option
  was removed in Consul 0.7.1. For later versions of Consul, you will need to reap
  processes using a wrapper, please see the [Consul Docker image entry point script](https://github.com/hashicorp/docker-consul/blob/master/0.X/docker-entrypoint.sh)
  for an example. If you are using Docker 1.13.0 or later, you can use the new `--init`
  option of the `docker run` command and docker will enable an init process with
  PID 1 that reaps child processes for the container. More info on [Docker docs](https://docs.docker.com/engine/reference/commandline/run/#options).

- `reconnect_timeout` This controls how long it
  takes for a failed node to be completely removed from the cluster. This defaults
  to 72 hours and it is recommended that this is set to at least double the maximum
  expected recoverable outage time for a node or network partition. WARNING: Setting
  this time too low could cause Consul servers to be removed from quorum during an
  extended node failure or partition, which could complicate recovery of the cluster.
  The value is a time with a unit suffix, which can be "s", "m", "h" for seconds,
  minutes, or hours. The value must be >= 8 hours.

- `reconnect_timeout_wan` This is the WAN equivalent
  of the [`reconnect_timeout`](#reconnect_timeout) parameter, which controls
  how long it takes for a failed server to be completely removed from the WAN pool.
  This also defaults to 72 hours, and must be >= 8 hours.

- `recursors` This flag provides addresses of upstream DNS
  servers that are used to recursively resolve queries if they are not inside the
  service domain for Consul. For example, a node can use Consul directly as a DNS
  server, and if the record is outside of the "consul." domain, the query will be
  resolved upstream. As of Consul 1.0.1 recursors can be provided as IP addresses
  or as go-sockaddr templates. IP addresses are resolved in order, and duplicates
  are ignored.

- `rpc` configuration for Consul servers.

  - `enable_streaming` ((#rpc_enable_streaming)) defaults to true. If set to false it will disable
    the gRPC subscribe endpoint on a Consul Server. All
    servers in all federated datacenters must have this enabled before any client can use
    [`use_streaming_backend`](#use_streaming_backend).

- `reporting`<EnterpriseAlert inline /> - This option allows options for HashiCorp reporting.
    - `license` - The license object allows users to control automatic reporting of license utilization metrics to HashiCorp.
      - `enabled`: (Defaults to `true`) Enables automatic license utilization reporting.

- `segment` <EnterpriseAlert inline /> - Equivalent to the [`-segment` command-line flag](/consul/docs/agent/config/cli-flags#_segment).

  ~> **Warning:** The `segment` option cannot be used with the [`partition`](#partition-1) option.

- `segments` <EnterpriseAlert inline /> - (Server agents only) This is a list of nested objects
  that specifies user-defined network segments, not including the `<default>` segment, which is
  created automatically. Refer to the [network segments documentation](/consul/docs/enterprise/network-segments/create-network-segment)for additional information.
  for more details.

  - `name` ((#segment_name)) - The name of the segment. Must be a string
    between 1 and 64 characters in length.
  - `bind` ((#segment_bind)) - The bind address to use for the segment's
    gossip layer. Defaults to the [`-bind`](#_bind) value if not provided.
  - `port` ((#segment_port)) - The port to use for the segment's gossip
    layer (required).
  - `advertise` ((#segment_advertise)) - The advertise address to use for
    the segment's gossip layer. Defaults to the [`-advertise`](/consul/docs/agent/config/cli-flags#_advertise) value
    if not provided.
  - `rpc_listener` ((#segment_rpc_listener)) - If true, a separate RPC
    listener will be started on this segment's [`-bind`](/consul/docs/agent/config/cli-flags#_bind) address on the rpc
    port. Only valid if the segment's bind address differs from the [`-bind`](/consul/docs/agent/config/cli-flags#_bind)
    address. Defaults to false.

- `server` Equivalent to the [`-server` command-line flag](/consul/docs/agent/config/cli-flags#_server).

- `server_rejoin_age_max` - controls the allowed maximum age of a stale server attempting to rejoin a cluster.
  If the server has not ran during this period, it will refuse to start up again until an operator intervenes by manually deleting the `server_metadata.json`
  file located in the data dir.
  This is to protect clusters from instability caused by decommissioned servers accidentally being started again.
  Note: the default value is 168h (equal to 7d) and the minimum value is 6h.

- `non_voting_server` - **This field is deprecated in Consul 1.9.1. See the [`read_replica`](#read_replica) field instead.**

- `read_replica` - Equivalent to the [`-read-replica` command-line flag](/consul/docs/agent/config/cli-flags#_read_replica).

- `session_ttl_min` The minimum allowed session TTL. This ensures sessions are not created with TTLs
  shorter than the specified limit. It is recommended to keep this limit at or above
  the default to encourage clients to send infrequent heartbeats. Defaults to 10s.

- `skip_leave_on_interrupt` This is similar
  to [`leave_on_terminate`](#leave_on_terminate) but only affects interrupt handling.
  When Consul receives an interrupt signal (such as hitting Control-C in a terminal),
  Consul will gracefully leave the cluster. Setting this to `true` disables that
  behavior. The default behavior for this feature varies based on whether or not
  the agent is running as a client or a server (prior to Consul 0.7 the default value
  was unconditionally set to `false`). On agents in client-mode, this defaults to
  `false` and for agents in server-mode, this defaults to `true` (i.e. Ctrl-C on
  a server will keep the server in the cluster and therefore quorum, and Ctrl-C on
  a client will gracefully leave).

- `translate_wan_addrs` If set to true, Consul
  will prefer a node's configured [WAN address](/consul/docs/agent/config/cli-flags#_advertise-wan)
  when servicing DNS and HTTP requests for a node in a remote datacenter. This allows
  the node to be reached within its own datacenter using its local address, and reached
  from other datacenters using its WAN address, which is useful in hybrid setups
  with mixed networks. This is disabled by default.

  Starting in Consul 0.7 and later, node addresses in responses to HTTP requests will also prefer a
  node's configured [WAN address](/consul/docs/agent/config/cli-flags#_advertise-wan) when querying for a node in a remote
  datacenter. An [`X-Consul-Translate-Addresses`](/consul/api-docs/api-structure#translated-addresses) header
  will be present on all responses when translation is enabled to help clients know that the addresses
  may be translated. The `TaggedAddresses` field in responses also have a `lan` address for clients that
  need knowledge of that address, regardless of translation.

  The following endpoints translate addresses:

  - [`/v1/catalog/nodes`](/consul/api-docs/catalog#list-nodes)
  - [`/v1/catalog/node/<node>`](/consul/api-docs/catalog#retrieve-map-of-services-for-a-node)
  - [`/v1/catalog/service/<service>`](/consul/api-docs/catalog#list-nodes-for-service)
  - [`/v1/health/service/<service>`](/consul/api-docs/health#list-nodes-for-service)
  - [`/v1/query/<query or name>/execute`](/consul/api-docs/query#execute-prepared-query)

- `unix_sockets` - This allows tuning the ownership and
  permissions of the Unix domain socket files created by Consul. Domain sockets are
  only used if the HTTP address is configured with the `unix://` prefix.

  It is important to note that this option may have different effects on
  different operating systems. Linux generally observes socket file permissions
  while many BSD variants ignore permissions on the socket file itself. It is
  important to test this feature on your specific distribution. This feature is
  currently not functional on Windows hosts.

  The following options are valid within this construct and apply globally to all
  sockets created by Consul:

  - `user` - The name or ID of the user who will own the socket file.
  - `group` - The group ID ownership of the socket file. This option
    currently only supports numeric IDs.
  - `mode` - The permission bits to set on the file.

- `use_streaming_backend` defaults to true. When enabled Consul client agents will use
  streaming rpc, instead of the traditional blocking queries, for endpoints which support
  streaming. All servers must have [`rpc.enable_streaming`](#rpc_enable_streaming)
  enabled before any client can enable `use_streaming_backend`.

- `watches` - Watches is a list of watch specifications which
  allow an external process to be automatically invoked when a particular data view
  is updated. See the [watch documentation](/consul/docs/dynamic-app-config/watches) for more detail.
  Watches can be modified when the configuration is reloaded.

## ACL Parameters

- `acl` ((#acl)) - This object allows a number of sub-keys to be set which
  controls the ACL system. Configuring the ACL system within the ACL stanza was added
  in Consul 1.4.0

  The following sub-keys are available:

  - `enabled` ((#acl_enabled)) - Enables ACLs.

  - `policy_ttl` ((#acl_policy_ttl)) - Used to control Time-To-Live caching
    of ACL policies. By default, this is 30 seconds. This setting has a major performance
    impact: reducing it will cause more frequent refreshes while increasing it reduces
    the number of refreshes. However, because the caches are not actively invalidated,
    ACL policy may be stale up to the TTL value.

  - `role_ttl` ((#acl_role_ttl)) - Used to control Time-To-Live caching
    of ACL roles. By default, this is 30 seconds. This setting has a major performance
    impact: reducing it will cause more frequent refreshes while increasing it reduces
    the number of refreshes. However, because the caches are not actively invalidated,
    ACL role may be stale up to the TTL value.

  - `token_ttl` ((#acl_token_ttl)) - Used to control Time-To-Live caching
    of ACL tokens. By default, this is 30 seconds. This setting has a major performance
    impact: reducing it will cause more frequent refreshes while increasing it reduces
    the number of refreshes. However, because the caches are not actively invalidated,
    ACL token may be stale up to the TTL value.

  - `down_policy` ((#acl_down_policy)) - Either "allow", "deny", "extend-cache"
    or "async-cache"; "extend-cache" is the default. In the case that a policy or
    token cannot be read from the [`primary_datacenter`](#primary_datacenter) or
    leader node, the down policy is applied. In "allow" mode, all actions are permitted,
    "deny" restricts all operations, and "extend-cache" allows any cached objects
    to be used, ignoring the expiry time of the cached entry. If the request uses an
    ACL that is not in the cache, "extend-cache" falls back to the behavior of
    `default_policy`.
    The value "async-cache" acts the same way as "extend-cache"
    but performs updates asynchronously when ACL is present but its TTL is expired,
    thus, if latency is bad between the primary and secondary datacenters, latency
    of operations is not impacted.

  - `default_policy` ((#acl_default_policy)) - Either "allow" or "deny";
    defaults to "allow" but this will be changed in a future major release. The default
    policy controls the behavior of a token when there is no matching rule. In "allow"
    mode, ACLs are a denylist: any operation not specifically prohibited is allowed.
    In "deny" mode, ACLs are an allowlist: any operation not specifically
    allowed is blocked. **Note**: this will not take effect until you've enabled ACLs.

  - `enable_key_list_policy` ((#acl_enable_key_list_policy)) - Boolean value, defaults to false.
    When true, the `list` permission will be required on the prefix being recursively read from the KV store.
    Regardless of being enabled, the full set of KV entries under the prefix will be filtered
    to remove any entries that the request's ACL token does not grant at least read
    permissions. This option is only available in Consul 1.0 and newer.

  - `enable_token_replication` ((#acl_enable_token_replication)) - By default
    secondary Consul datacenters will perform replication of only ACL policies and
    roles. Setting this configuration will will enable ACL token replication and
    allow for the creation of both [local tokens](/consul/api-docs/acl/tokens#local) and
    [auth methods](/consul/docs/security/acl/auth-methods) in connected secondary datacenters.

    ~> **Warning:** When enabling ACL token replication on the secondary datacenter,
    global tokens already present in the secondary datacenter will be lost. For
    production environments, consider configuring ACL replication in your initial
    datacenter bootstrapping process.

  - `enable_token_persistence` ((#acl_enable_token_persistence)) - Either
    `true` or `false`. When `true` tokens set using the API will be persisted to
    disk and reloaded when an agent restarts.

  - `tokens` ((#acl_tokens)) - This object holds all of the configured
    ACL tokens for the agents usage.

    - `initial_management` ((#acl_tokens_initial_management)) - This is available in
      Consul 1.11 and later. In prior versions, use [`acl.tokens.master`](#acl_tokens_master).

      Only used for servers in the [`primary_datacenter`](#primary_datacenter).
      This token will be created with management-level permissions if it does not exist.
      It allows operators to bootstrap the ACL system with a token Secret ID that is
      well-known.

      The `initial_management` token is only installed when a server acquires cluster
      leadership. If you would like to install or change it, set the new value for
      `initial_management` in the configuration for all servers. Once this is done,
      restart the current leader to force a leader election. If the `initial_management`
      token is not supplied, then the servers do not create an initial management token.
      When you provide a value, it should be a UUID. To maintain backwards compatibility
      and an upgrade path this restriction is not currently enforced but will be in a
      future major Consul release.

    - `master` ((#acl_tokens_master)) **Renamed in Consul 1.11 to
      [`acl.tokens.initial_management`](#acl_tokens_initial_management).**

    - `default` ((#acl_tokens_default)) - When provided, this agent will
      use this token by default when making requests to the Consul servers
      instead of the [anonymous token](/consul/docs/security/acl/tokens#anonymous-token).
      Consul HTTP API requests can provide an alternate token in their authorization header
      to override the `default` or anonymous token on a per-request basis,
      as described in [HTTP API Authentication](/consul/api-docs/api-structure#authentication).

    - `agent` ((#acl_tokens_agent)) - Used for clients and servers to perform
      internal operations. If this isn't specified, then the
      [`default`](#acl_tokens_default) will be used.

      This token must at least have write access to the node name it will
      register as in order to set any of the node-level information in the
      catalog such as metadata, or the node's tagged addresses.

    - `agent_recovery` ((#acl_tokens_agent_recovery)) - This is available in Consul 1.11
      and later. In prior versions, use [`acl.tokens.agent_master`](#acl_tokens_agent_master).

      Used to access [agent endpoints](/consul/api-docs/agent) that require agent read or write privileges,
      or node read privileges, even if Consul servers aren't present to validate any tokens.
      This should only be used by operators during outages, regular ACL tokens should normally
      be used by applications.

    - `agent_master` ((#acl_tokens_agent_master)) **Renamed in Consul 1.11 to
      [`acl.tokens.agent_recovery`](#acl_tokens_agent_recovery).**

    - `config_file_service_registration` ((#acl_tokens_config_file_service_registration)) - Specifies the ACL
      token the agent uses to register services and checks from [service](/consul/docs/services/usage/define-services) and [check](/consul/docs/services/usage/checks) definitions
      specified in configuration files or fragments passed to the agent using the `-hcl`
      flag.

      If the `token` field is defined in the service or check definition, then that token is used to
      register the service or check instead. If the `config_file_service_registration` token is not
      defined and if the `token` field is not defined in the service or check definition, then the
      agent uses the [`default`](#acl_tokens_default) token to register the service or check.

      This token needs write permission to register all services and checks defined in this agent's
      configuration. For example, if there are two service definitions in the agent's configuration
      files for services "A" and "B", then the token needs `service:write` permissions for both
      services "A" and "B" in order to successfully register both services. If the token is missing
      `service:write` permissions for service "B", the agent will successfully register service "A"
      and fail to register service "B". Failed registration requests are eventually retried as part
      of [anti-entropy enforcement](/consul/docs/architecture/anti-entropy). If a registration request is
      failing due to missing permissions, the the token for this agent can be updated with
      additional policy rules or the `config_file_service_registration` token can be replaced using
      the [Set Agent Token](/consul/commands/acl/set-agent-token) CLI command.

    - `replication` ((#acl_tokens_replication)) - The ACL token used to
      authorize secondary datacenters with the primary datacenter for replication
      operations. This token is required for servers outside the [`primary_datacenter`](#primary_datacenter) when ACLs are enabled. This token may be provided later using the [agent token API](/consul/api-docs/agent#update-acl-tokens) on each server. This token must have at least "read" permissions on ACL data but if ACL token replication is enabled then it must have "write" permissions. This also enables service mesh data replication, for which the token will require both operator "write" and intention "read" permissions for replicating CA and Intention data.

      ~> **Warning:** When enabling ACL token replication on the secondary datacenter,
      policies and roles already present in the secondary datacenter will be lost. For
      production environments, consider configuring ACL replication in your initial
      datacenter bootstrapping process.

    - `managed_service_provider` ((#acl_tokens_managed_service_provider)) <EnterpriseAlert inline /> - An
      array of ACL tokens used by Consul managed service providers for cluster operations.

      <CodeTabs heading="Example managed_service_provider configuration">

      ```hcl
      managed_service_provider {
        accessor_id = "ed22003b-0832-4e48-ac65-31de64e5c2ff"
        secret_id = "cb6be010-bba8-4f30-a9ed-d347128dde17"
      }
      ```

      ```json
      "managed_service_provider": [
        {
          "accessor_id": "ed22003b-0832-4e48-ac65-31de64e5c2ff",
          "secret_id": "cb6be010-bba8-4f30-a9ed-d347128dde17"
        }
      ]
      ```

      </CodeTabs>

- `acl_datacenter` - **This field is deprecated in Consul 1.4.0. See the [`primary_datacenter`](#primary_datacenter) field instead.**

  This designates the datacenter which is authoritative for ACL information. It must be provided to enable ACLs. All servers and datacenters must agree on the ACL datacenter. Setting it on the servers is all you need for cluster-level enforcement, but for the APIs to forward properly from the clients,
  it must be set on them too. In Consul 0.8 and later, this also enables agent-level enforcement
  of ACLs. Please review the [ACL tutorial](/consul/tutorials/security/access-control-setup-production) for more details.

- `acl_default_policy` ((#acl_default_policy_legacy)) - **Deprecated in Consul 1.4.0. See the [`acl.default_policy`](#acl_default_policy) field instead.**
  Either "allow" or "deny"; defaults to "allow". The default policy controls the
  behavior of a token when there is no matching rule. In "allow" mode, ACLs are a
  denylist: any operation not specifically prohibited is allowed. In "deny" mode,
  ACLs are an allowlist: any operation not specifically allowed is blocked. **Note**:
  this will not take effect until you've set `primary_datacenter` to enable ACL support.

- `acl_down_policy` ((#acl_down_policy_legacy)) - **Deprecated in Consul
  1.4.0. See the [`acl.down_policy`](#acl_down_policy) field instead.** Either "allow",
  "deny", "extend-cache" or "async-cache"; "extend-cache" is the default. In the
  case that the policy for a token cannot be read from the [`primary_datacenter`](#primary_datacenter)
  or leader node, the down policy is applied. In "allow" mode, all actions are permitted,
  "deny" restricts all operations, and "extend-cache" allows any cached ACLs to be
  used, ignoring their TTL values. If a non-cached ACL is used, "extend-cache" acts
  like "deny". The value "async-cache" acts the same way as "extend-cache" but performs
  updates asynchronously when ACL is present but its TTL is expired, thus, if latency
  is bad between ACL authoritative and other datacenters, latency of operations is
  not impacted.

- `acl_agent_master_token` ((#acl_agent_master_token_legacy)) - **Deprecated
  in Consul 1.4.0. See the [`acl.tokens.agent_master`](#acl_tokens_agent_master)
  field instead.** Used to access [agent endpoints](/consul/api-docs/agent) that
  require agent read or write privileges, or node read privileges, even if Consul
  servers aren't present to validate any tokens. This should only be used by operators
  during outages, regular ACL tokens should normally be used by applications. This
  was added in Consul 0.7.2 and is only used when [`acl_enforce_version_8`](#acl_enforce_version_8) is set to true.

- `acl_agent_token` ((#acl_agent_token_legacy)) - **Deprecated in Consul
  1.4.0. See the [`acl.tokens.agent`](#acl_tokens_agent) field instead.** Used for
  clients and servers to perform internal operations. If this isn't specified, then
  the [`acl_token`](#acl_token) will be used. This was added in Consul 0.7.2.

  This token must at least have write access to the node name it will register as in order to set any
  of the node-level information in the catalog such as metadata, or the node's tagged addresses.

- `acl_enforce_version_8` - **Deprecated in
  Consul 1.4.0 and removed in 1.8.0.** Used for clients and servers to determine if enforcement should
  occur for new ACL policies being previewed before Consul 0.8. Added in Consul 0.7.2,
  this defaults to false in versions of Consul prior to 0.8, and defaults to true
  in Consul 0.8 and later. This helps ease the transition to the new ACL features
  by allowing policies to be in place before enforcement begins.

- `acl_master_token` ((#acl_master_token_legacy)) - **Deprecated in Consul
  1.4.0. See the [`acl.tokens.master`](#acl_tokens_master) field instead.**

- `acl_replication_token` ((#acl_replication_token_legacy)) - **Deprecated
  in Consul 1.4.0. See the [`acl.tokens.replication`](#acl_tokens_replication) field
  instead.** Only used for servers outside the [`primary_datacenter`](#primary_datacenter)
  running Consul 0.7 or later. When provided, this will enable [ACL replication](/consul/tutorials/security-operations/access-control-replication-multiple-datacenters)
  using this ACL replication using this token to retrieve and replicate the ACLs
  to the non-authoritative local datacenter. In Consul 0.9.1 and later you can enable
  ACL replication using [`acl.enable_token_replication`](#acl_enable_token_replication) and then
  set the token later using the [agent token API](/consul/api-docs/agent#update-acl-tokens)
  on each server. If the `acl_replication_token` is set in the config, it will automatically
  set [`acl.enable_token_replication`](#acl_enable_token_replication) to true for backward compatibility.

  If there's a partition or other outage affecting the authoritative datacenter, and the
  [`acl_down_policy`](/consul/docs/agent/config/config-files#acl_down_policy) is set to "extend-cache", tokens not
  in the cache can be resolved during the outage using the replicated set of ACLs.

- `acl_token` ((#acl_token_legacy)) - **Deprecated in Consul 1.4.0. See
  the [`acl.tokens.default`](#acl_tokens_default) field instead.**

- `acl_ttl` ((#acl_ttl_legacy)) - **Deprecated in Consul 1.4.0. See the
  [`acl.token_ttl`](#acl_token_ttl) field instead.**Used to control Time-To-Live
  caching of ACLs. By default, this is 30 seconds. This setting has a major performance
  impact: reducing it will cause more frequent refreshes while increasing it reduces
  the number of refreshes. However, because the caches are not actively invalidated,
  ACL policy may be stale up to the TTL value.

- `enable_acl_replication` **Deprecated in Consul 1.11. Use the [`acl.enable_token_replication`](#acl_enable_token_replication) field instead.**
  When set on a Consul server, enables ACL replication without having to set
  the replication token via [`acl_replication_token`](#acl_replication_token). Instead, enable ACL replication
  and then introduce the token using the [agent token API](/consul/api-docs/agent#update-acl-tokens) on each server.
  See [`acl_replication_token`](#acl_replication_token) for more details.

  ~> **Warning:** When enabling ACL token replication on the secondary datacenter,
  policies and roles already present in the secondary datacenter will be lost. For
  production environments, consider configuring ACL replication in your initial
  datacenter bootstrapping process.

## Advertise Address Parameters

- `advertise_addr` Equivalent to the [`-advertise` command-line flag](/consul/docs/agent/config/cli-flags#_advertise).

- `advertise_addr_ipv4` This was added together with [`advertise_addr_ipv6`](#advertise_addr_ipv6) to support dual stack IPv4/IPv6 environments. Using this, both IPv4 and IPv6 addresses can be specified and requested during eg service discovery.

- `advertise_addr_ipv6` This was added together with [`advertise_addr_ipv4`](#advertise_addr_ipv4) to support dual stack IPv4/IPv6 environments. Using this, both IPv4 and IPv6 addresses can be specified and requested during eg service discovery.

- `advertise_addr_wan` Equivalent to the [`-advertise-wan` command-line flag](/consul/docs/agent/config/cli-flags#_advertise-wan).

- `advertise_addr_wan_ipv4` This was added together with [`advertise_addr_wan_ipv6`](#advertise_addr_wan_ipv6) to support dual stack IPv4/IPv6 environments. Using this, both IPv4 and IPv6 addresses can be specified and requested during eg service discovery.

- `advertise_addr_wan_ipv6` This was added together with [`advertise_addr_wan_ipv4`](#advertise_addr_wan_ipv4) to support dual stack IPv4/IPv6 environments. Using this, both IPv4 and IPv6 addresses can be specified and requested during eg service discovery.

- `advertise_reconnect_timeout` This is a per-agent setting of the [`reconnect_timeout`](#reconnect_timeout) parameter.
  This agent will advertise to all other nodes in the cluster that after this timeout, the node may be completely
  removed from the cluster. This may only be set on client agents and if unset then other nodes will use the main
  `reconnect_timeout` setting when determining when this node may be removed from the cluster.

## Bootstrap Parameters

- `bootstrap` Equivalent to the [`-bootstrap` command-line flag](/consul/docs/agent/config/cli-flags#_bootstrap).

- `bootstrap_expect` Equivalent to the [`-bootstrap-expect` command-line flag](/consul/docs/agent/config/cli-flags#_bootstrap_expect).

## Self-managed HCP Parameters

- `cloud` This object specifies settings for connecting self-managed clusters to HCP. This was added in Consul 1.14

  - `client_id` The OAuth2 client ID for authentication with HCP. This can be overridden using the `HCP_CLIENT_ID` environment variable.

  - `client_secret` The OAuth2 client secret for authentication with HCP. This can be overridden using the `HCP_CLIENT_SECRET` environment variable.

  - `resource_id` The HCP resource identifier. This can be overridden using the `HCP_RESOURCE_ID` environment variable.

## Service Mesh Parameters ((#connect-parameters))

The noun _connect_ is used throughout this documentation to refer to the connect
subsystem that provides Consul's service mesh capabilities.

- `connect` This object allows setting options for the Connect feature.

  The following sub-keys are available:

  - `enabled` ((#connect_enabled)) (Defaults to `true`) Controls whether Connect features are
    enabled on this agent. Should be enabled on all servers in the cluster
    in order for service mesh to function properly.
    Will be set to `true` automatically if `auto_config.enabled` or `auto_encrypt.allow_tls` is `true`.

  - `enable_mesh_gateway_wan_federation` ((#connect_enable_mesh_gateway_wan_federation)) (Defaults to `false`) Controls whether cross-datacenter federation traffic between servers is funneled
    through mesh gateways. This was added in Consul 1.8.0.

  - `ca_provider` ((#connect_ca_provider)) Controls which CA provider to
    use for the service mesh's CA. Currently only the `aws-pca`, `consul`, and `vault` providers are supported.
    This is only used when initially bootstrapping the cluster. For an existing cluster,
    use the [Update CA Configuration Endpoint](/consul/api-docs/connect/ca#update-ca-configuration).

  - `ca_config` ((#connect_ca_config)) An object which allows setting different
    config options based on the CA provider chosen. This is only used when initially
    bootstrapping the cluster. For an existing cluster, use the [Update CA Configuration
    Endpoint](/consul/api-docs/connect/ca#update-ca-configuration).

    The following providers are supported:

    #### AWS ACM Private CA Provider (`ca_provider = "aws-pca"`)

    - `existing_arn` ((#aws_ca_existing_arn)) The Amazon Resource Name (ARN) of
      an existing private CA in your ACM account. If specified, Consul will
      attempt to use the existing CA to issue certificates.

    #### Consul CA Provider (`ca_provider = "consul"`)

    - `private_key` ((#consul_ca_private_key)) The PEM contents of the
      private key to use for the CA.

    - `root_cert` ((#consul_ca_root_cert)) The PEM contents of the root
      certificate to use for the CA.

    #### Vault CA Provider (`ca_provider = "vault"`)

    - `address` ((#vault_ca_address)) The address of the Vault server to
      connect to.

    - `token` ((#vault_ca_token)) The Vault token to use. In Consul 1.8.5 and later, if
      the token has the [renewable](/vault/api-docs/auth/token#renewable)
      flag set, Consul will attempt to renew its lease periodically after half the
      duration has expired.

    - `root_pki_path` ((#vault_ca_root_pki)) The path to use for the root
      CA pki backend in Vault. This can be an existing backend with a CA already
      configured, or a blank/unmounted backend in which case Consul will automatically
      mount/generate the CA. The Vault token given above must have `sudo` access
      to this backend, as well as permission to mount the backend at this path if
      it is not already mounted.

    - `intermediate_pki_path` ((#vault_ca_intermediate_pki))
      The path to use for the temporary intermediate CA pki backend in Vault. **Consul
      will overwrite any data at this path in order to generate a temporary intermediate
      CA**. The Vault token given above must have `write` access to this backend,
      as well as permission to mount the backend at this path if it is not already
      mounted.

    - `auth_method` ((#vault_ca_auth_method))
      Vault auth method to use for logging in to Vault.
      Please see [Vault Auth Methods](/vault/docs/auth) for more information
      on how to configure individual auth methods. If auth method is provided, Consul will obtain a
      new token from Vault when the token can no longer be renewed.

       - `type` The type of Vault auth method.

       - `mount_path` The mount path of the auth method.
      If not provided the auth method type will be used as the mount path.

       - `params` The parameters to configure the auth method.
      Please see [Vault Auth Methods](/vault/docs/auth) for information on how
      to configure the auth method you wish to use. If using the Kubernetes auth method, Consul will
      read the service account token from the default mount path `/var/run/secrets/kubernetes.io/serviceaccount/token`
      if the `jwt` parameter is not provided.

    #### Common CA Config Options

    There are also a number of common configuration options supported by all providers:

    - `csr_max_concurrent` ((#ca_csr_max_concurrent)) Sets a limit on the number
      of Certificate Signing Requests that can be processed concurrently. Defaults
      to 0 (disabled). This is useful when you want to limit the number of CPU cores
      available to the server for certificate signing operations. For example, on an
      8 core server, setting this to 1 will ensure that no more than one CPU core
      will be consumed when generating or rotating certificates. Setting this is
      recommended **instead** of `csr_max_per_second` when you want to limit the
      number of cores consumed since it is simpler to reason about limiting CSR
      resources this way without artificially slowing down rotations. Added in 1.4.1.

    - `csr_max_per_second` ((#ca_csr_max_per_second)) Sets a rate limit
      on the maximum number of Certificate Signing Requests (CSRs) the servers will
      accept. This is used to prevent CA rotation from causing unbounded CPU usage
      on servers. It defaults to 50 which is conservative – a 2017 Macbook can process
      about 100 per second using only ~40% of one CPU core – but sufficient for deployments
      up to ~1500 service instances before the time it takes to rotate is impacted.
      For larger deployments we recommend increasing this based on the expected number
      of server instances and server resources, or use `csr_max_concurrent` instead
      if servers have more than one CPU core. Setting this to zero disables rate limiting.
      Added in 1.4.1.

    - `leaf_cert_ttl` ((#ca_leaf_cert_ttl)) Specifies the upper bound on the expiry
      of a leaf certificate issued for a service. In most cases a new leaf
      certificate will be requested by a proxy before this limit is reached. This
      is also the effective limit on how long a server outage can last (with no leader)
      before network connections will start being rejected. Defaults to `72h`.

      You can specify a range from one hour (minimum) up to one year (maximum) using
      the following units: `h`, `m`, `s`, `ms`, `us` (or `µs`), `ns`, or a combination
      of those units, e.g. `1h5m`.

      This value is also used when rotating out old root certificates from
      the cluster. When a root certificate has been inactive (rotated out)
      for more than twice the _current_ `leaf_cert_ttl`, it will be removed
      from the trusted list.

    - `intermediate_cert_ttl` ((#ca_intermediate_cert_ttl)) Specifies the expiry for the
      intermediate certificates. Defaults to `8760h` (1 year). Must be at least 3 times `leaf_cert_ttl`.

    - `root_cert_ttl` ((#ca_root_cert_ttl)) Specifies the expiry for a root certificate.
      Defaults to 10 years as `87600h`. This value, if provided, needs to be higher than the
      intermediate certificate TTL.

      This setting applies to all Consul CA providers.

      For the Vault provider, this value is only used if the backend is not initialized at first.

      This value is also applied on the `ca set-config` command.

    - `private_key_type` ((#ca_private_key_type)) The type of key to generate
      for this CA. This is only used when the provider is generating a new key. If
      `private_key` is set for the Consul provider, or existing root or intermediate
      PKI paths given for Vault then this will be ignored. Currently supported options
      are `ec` or `rsa`. Default is `ec`.

      It is required that all servers in a datacenter have
      the same config for the CA. It is recommended that servers in
      different datacenters use the same key type and size,
      although the built-in CA and Vault provider will both allow mixed CA
      key types.

      Some CA providers (currently Vault) will not allow cross-signing a
      new CA certificate with a different key type. This means that if you
      migrate from an RSA-keyed Vault CA to an EC-keyed CA from any
      provider, you may have to proceed without cross-signing which risks
      temporary connection issues for workloads during the new certificate
      rollout. We highly recommend testing this outside of production to
      understand the impact and suggest sticking to same key type where
      possible.

      Note that this only affects _CA_ keys generated by the provider.
      Leaf certificate keys are always EC 256 regardless of the CA
      configuration.

    - `private_key_bits` ((#ca_private_key_bits)) The length of key to
      generate for this CA. This is only used when the provider is generating a new
      key. If `private_key` is set for the Consul provider, or existing root or intermediate
      PKI paths given for Vault then this will be ignored.

      Currently supported values are:

      - `private_key_type = ec` (default): `224, 256, 384, 521`
        corresponding to the NIST P-\* curves of the same name.
      - `private_key_type = rsa`: `2048, 4096`

## DNS and Domain Parameters

- `dns_config` This object allows a number of sub-keys
  to be set which can tune how DNS queries are serviced. Check the tutorial on [DNS caching](/consul/tutorials/networking/dns-caching) for more detail.

  The following sub-keys are available:

  - `allow_stale` - Enables a stale query for DNS information.
    This allows any Consul server, rather than only the leader, to service the request.
    The advantage of this is you get linear read scalability with Consul servers.
    In versions of Consul prior to 0.7, this defaulted to false, meaning all requests
    are serviced by the leader, providing stronger consistency but less throughput
    and higher latency. In Consul 0.7 and later, this defaults to true for better
    utilization of available servers.

  - `max_stale` - When [`allow_stale`](#allow_stale) is
    specified, this is used to limit how stale results are allowed to be. If a Consul
    server is behind the leader by more than `max_stale`, the query will be re-evaluated
    on the leader to get more up-to-date results. Prior to Consul 0.7.1 this defaulted
    to 5 seconds; in Consul 0.7.1 and later this defaults to 10 years ("87600h")
    which effectively allows DNS queries to be answered by any server, no matter
    how stale. In practice, servers are usually only milliseconds behind the leader,
    so this lets Consul continue serving requests in long outage scenarios where
    no leader can be elected.

  - `node_ttl` - By default, this is "0s", so all node lookups
    are served with a 0 TTL value. DNS caching for node lookups can be enabled by
    setting this value. This should be specified with the "s" suffix for second or
    "m" for minute.

  - `service_ttl` - This is a sub-object which allows
    for setting a TTL on service lookups with a per-service policy. The "\*" wildcard
    service can be used when there is no specific policy available for a service.
    By default, all services are served with a 0 TTL value. DNS caching for service
    lookups can be enabled by setting this value.

  - `enable_truncate` - If set to true, a UDP DNS
    query that would return more than 3 records, or more than would fit into a valid
    UDP response, will set the truncated flag, indicating to clients that they should
    re-query using TCP to get the full set of records.

  - `only_passing` - If set to true, any nodes whose
    health checks are warning or critical will be excluded from DNS results. If false,
    the default, only nodes whose health checks are failing as critical will be excluded.
    For service lookups, the health checks of the node itself, as well as the service-specific
    checks are considered. For example, if a node has a health check that is critical
    then all services on that node will be excluded because they are also considered
    critical.

  - `recursor_strategy` - If set to `sequential`, Consul will query recursors in the
    order listed in the [`recursors`](#recursors) option. If set to `random`,
    Consul will query an upstream DNS resolvers in a random order. Defaults to
    `sequential`.

  - `recursor_timeout` - Timeout used by Consul when
    recursively querying an upstream DNS server. See [`recursors`](#recursors) for more details. Default is 2s. This is available in Consul 0.7 and later.

  - `disable_compression` - If set to true, DNS
    responses will not be compressed. Compression was added and enabled by default
    in Consul 0.7.

  - `udp_answer_limit` - Limit the number of resource
    records contained in the answer section of a UDP-based DNS response. This parameter
    applies only to UDP DNS queries that are less than 512 bytes. This setting is
    deprecated and replaced in Consul 1.0.7 by [`a_record_limit`](#a_record_limit).

  - `a_record_limit` - Limit the number of resource
    records contained in the answer section of a A, AAAA or ANY DNS response (both
    TCP and UDP). When answering a question, Consul will use the complete list of
    matching hosts, shuffle the list randomly, and then limit the number of answers
    to `a_record_limit` (default: no limit). This limit does not apply to SRV records.

    In environments where [RFC 3484 Section 6](https://tools.ietf.org/html/rfc3484#section-6) Rule 9
    is implemented and enforced (i.e. DNS answers are always sorted and
    therefore never random), clients may need to set this value to `1` to
    preserve the expected randomized distribution behavior (note:
    [RFC 3484](https://tools.ietf.org/html/rfc3484) has been obsoleted by
    [RFC 6724](https://tools.ietf.org/html/rfc6724) and as a result it should
    be increasingly uncommon to need to change this value with modern
    resolvers).

  - `enable_additional_node_meta_txt` - When set to true, Consul
    will add TXT records for Node metadata into the Additional section of the DNS responses for several query types such as SRV queries. When set to false those records are not emitted. This does not impact the behavior of those same TXT records when they would be added to the Answer section of the response like when querying with type TXT or ANY. This defaults to true.

  - `soa` Allow to tune the setting set up in SOA. Non specified
    values fallback to their default values, all values are integers and expressed
    as seconds.

    The following settings are available:

    - `expire` ((#soa_expire)) - Configure SOA Expire duration in seconds,
      default value is 86400, ie: 24 hours.

    - `min_ttl` ((#soa_min_ttl)) - Configure SOA DNS minimum TTL. As explained
      in [RFC-2308](https://tools.ietf.org/html/rfc2308) this also controls negative
      cache TTL in most implementations. Default value is 0, ie: no minimum delay
      or negative TTL.

    - `refresh` ((#soa_refresh)) - Configure SOA Refresh duration in seconds,
      default value is `3600`, ie: 1 hour.

    - `retry` ((#soa_retry)) - Configures the Retry duration expressed
      in seconds, default value is 600, ie: 10 minutes.

  - `use_cache` ((#dns_use_cache)) - When set to true, DNS resolution will
    use the agent cache described in [agent caching](/consul/api-docs/features/caching).
    This setting affects all service and prepared queries DNS requests. Implies [`allow_stale`](#allow_stale)

  - `cache_max_age` ((#dns_cache_max_age)) - When [use_cache](#dns_use_cache)
    is enabled, the agent will attempt to re-fetch the result from the servers if
    the cached value is older than this duration. See: [agent caching](/consul/api-docs/features/caching).

    **Note** that unlike the `max-age` HTTP header, a value of 0 for this field is
    equivalent to "no max age". To get a fresh value from the cache use a very small value
    of `1ns` instead of 0.

  - `prefer_namespace` ((#dns_prefer_namespace)) <EnterpriseAlert inline /> **Deprecated in Consul 1.11.
    Use the [canonical DNS format for enterprise service lookups](/consul/docs/services/discovery/dns-static-lookups#service-lookups-for-consul-enterprise) instead.** -
    When set to `true`, in a DNS query for a service, a single label between the domain
    and the `service` label is treated as a namespace name instead of a datacenter.
    When set to `false`, the default, the behavior is the same as non-Enterprise
    versions and treats the single label as the datacenter.

- `domain` Equivalent to the [`-domain` command-line flag](/consul/docs/agent/config/cli-flags#_domain).

## Encryption Parameters

- `auto_encrypt` This object allows setting options for the `auto_encrypt` feature.

  The following sub-keys are available:

  - `allow_tls` (Defaults to `false`) This option enables
    `auto_encrypt` on the servers and allows them to automatically distribute certificates
    from the service mesh CA to the clients. If enabled, the server can accept incoming
    connections from both the built-in CA and the service mesh CA, as well as their certificates.
    Note, the server will only present the built-in CA and certificate, which the
    client can verify using the CA it received from `auto_encrypt` endpoint. If disabled,
    a client configured with `auto_encrypt.tls` will be unable to start.

  - `tls` (Defaults to `false`) Allows the client to request the
    service mesh CA and certificates from the servers, for encrypting RPC communication.
    The client will make the request to any servers listed in the `-retry-join`
    option. This requires that every server to have `auto_encrypt.allow_tls` enabled.
    When both `auto_encrypt` options are used, it allows clients to receive certificates
    that are generated on the servers. If the `-server-port` is not the default one,
    it has to be provided to the client as well. Usually this is discovered through
    LAN gossip, but `auto_encrypt` provision happens before the information can be
    distributed through gossip. The most secure `auto_encrypt` setup is when the
    client is provided with the built-in CA, `verify_server_hostname` is turned on,
    and when an ACL token with `node.write` permissions is setup. It is also possible
    to use `auto_encrypt` with a CA and ACL, but without `verify_server_hostname`,
    or only with a ACL enabled, or only with CA and `verify_server_hostname`, or
    only with a CA, or finally without a CA and without ACL enabled. In any case,
    the communication to the `auto_encrypt` endpoint is always TLS encrypted.

    ~> **Warning:** Enabling `auto_encrypt.tls` conflicts with the [`auto_config`](#auto_config) feature.
    Only one option may be specified.

  - `dns_san` (Defaults to `[]`) When this option is being
    used, the certificates requested by `auto_encrypt` from the server have these
    `dns_san` set as DNS SAN.

  - `ip_san` (Defaults to `[]`) When this option is being used,
    the certificates requested by `auto_encrypt` from the server have these `ip_san`
    set as IP SAN.

- `encrypt` Equivalent to the [`-encrypt` command-line flag](/consul/docs/agent/config/cli-flags#_encrypt).

- `encrypt_verify_incoming` - This is an optional
  parameter that can be used to disable enforcing encryption for incoming gossip
  in order to upshift from unencrypted to encrypted gossip on a running cluster.
  See [this section](/consul/docs/security/encryption#configuring-gossip-encryption-on-an-existing-cluster)
  for more information. Defaults to true.

- `encrypt_verify_outgoing` - This is an optional
  parameter that can be used to disable enforcing encryption for outgoing gossip
  in order to upshift from unencrypted to encrypted gossip on a running cluster.
  See [this section](/consul/docs/security/encryption#configuring-gossip-encryption-on-an-existing-cluster)
  for more information. Defaults to true.

## Gossip Parameters

- `gossip_lan` - **(Advanced)** This object contains a
  number of sub-keys which can be set to tune the LAN gossip communications. These
  are only provided for users running especially large clusters that need fine tuning
  and are prepared to spend significant effort correctly tuning them for their environment
  and workload. **Tuning these improperly can cause Consul to fail in unexpected
  ways**. The default values are appropriate in almost all deployments.

  - `gossip_nodes` - The number of random nodes to send
    gossip messages to per gossip_interval. Increasing this number causes the gossip
    messages to propagate across the cluster more quickly at the expense of increased
    bandwidth. The default is 3.

  - `gossip_interval` - The interval between sending
    messages that need to be gossiped that haven't been able to piggyback on probing
    messages. If this is set to zero, non-piggyback gossip is disabled. By lowering
    this value (more frequent) gossip messages are propagated across the cluster
    more quickly at the expense of increased bandwidth. The default is 200ms.

  - `probe_interval` - The interval between random
    node probes. Setting this lower (more frequent) will cause the cluster to detect
    failed nodes more quickly at the expense of increased bandwidth usage. The default
    is 1s.

  - `probe_timeout` - The timeout to wait for an ack
    from a probed node before assuming it is unhealthy. This should be at least the
    99-percentile of RTT (round-trip time) on your network. The default is 500ms
    and is a conservative value suitable for almost all realistic deployments.

  - `retransmit_mult` - The multiplier for the number
    of retransmissions that are attempted for messages broadcasted over gossip. The
    number of retransmits is scaled using this multiplier and the cluster size. The
    higher the multiplier, the more likely a failed broadcast is to converge at the
    expense of increased bandwidth. The default is 4.

  - `suspicion_mult` - The multiplier for determining
    the time an inaccessible node is considered suspect before declaring it dead.
    The timeout is scaled with the cluster size and the probe_interval. This allows
    the timeout to scale properly with expected propagation delay with a larger cluster
    size. The higher the multiplier, the longer an inaccessible node is considered
    part of the cluster before declaring it dead, giving that suspect node more time
    to refute if it is indeed still alive. The default is 4.

- `gossip_wan` - **(Advanced)** This object contains a
  number of sub-keys which can be set to tune the WAN gossip communications. These
  are only provided for users running especially large clusters that need fine tuning
  and are prepared to spend significant effort correctly tuning them for their environment
  and workload. **Tuning these improperly can cause Consul to fail in unexpected
  ways**. The default values are appropriate in almost all deployments.

  - `gossip_nodes` - The number of random nodes to send
    gossip messages to per gossip_interval. Increasing this number causes the gossip
    messages to propagate across the cluster more quickly at the expense of increased
    bandwidth. The default is 4.

  - `gossip_interval` - The interval between sending
    messages that need to be gossiped that haven't been able to piggyback on probing
    messages. If this is set to zero, non-piggyback gossip is disabled. By lowering
    this value (more frequent) gossip messages are propagated across the cluster
    more quickly at the expense of increased bandwidth. The default is 500ms.

  - `probe_interval` - The interval between random
    node probes. Setting this lower (more frequent) will cause the cluster to detect
    failed nodes more quickly at the expense of increased bandwidth usage. The default
    is 5s.

  - `probe_timeout` - The timeout to wait for an ack
    from a probed node before assuming it is unhealthy. This should be at least the
    99-percentile of RTT (round-trip time) on your network. The default is 3s
    and is a conservative value suitable for almost all realistic deployments.

  - `retransmit_mult` - The multiplier for the number
    of retransmissions that are attempted for messages broadcasted over gossip. The
    number of retransmits is scaled using this multiplier and the cluster size. The
    higher the multiplier, the more likely a failed broadcast is to converge at the
    expense of increased bandwidth. The default is 4.

  - `suspicion_mult` - The multiplier for determining
    the time an inaccessible node is considered suspect before declaring it dead.
    The timeout is scaled with the cluster size and the probe_interval. This allows
    the timeout to scale properly with expected propagation delay with a larger cluster
    size. The higher the multiplier, the longer an inaccessible node is considered
    part of the cluster before declaring it dead, giving that suspect node more time
    to refute if it is indeed still alive. The default is 6.

## Join Parameters

- `rejoin_after_leave` Equivalent to the [`-rejoin` command-line flag](/consul/docs/agent/config/cli-flags#_rejoin).

- `retry_join` - Equivalent to the [`-retry-join`](/consul/docs/agent/config/cli-flags#retry-join) command-line flag.

- `retry_interval` Equivalent to the [`-retry-interval` command-line flag](/consul/docs/agent/config/cli-flags#_retry_interval).

- `retry_max` - Equivalent to the [`-retry-max`](/consul/docs/agent/config/cli-flags#_retry_max) command-line flag.

- `retry_join_wan` Equivalent to the [`-retry-join-wan` command-line flag](/consul/docs/agent/config/cli-flags#_retry_join_wan). Takes a list of addresses to attempt joining to WAN every [`retry_interval_wan`](#_retry_interval_wan) until at least one join works.

- `retry_interval_wan` Equivalent to the [`-retry-interval-wan` command-line flag](/consul/docs/agent/config/cli-flags#_retry_interval_wan).

- `start_join` **Deprecated in Consul 1.15. Use the [`retry_join`](/consul/docs/agent/config/config-files#retry_join) field instead. This field will be removed in a future version of Consul.**
  This field is an alias of `retry_join`.

- `start_join_wan` **Deprecated in Consul 1.15. Use the [`retry_join_wan`](/consul/docs/agent/config/config-files#retry_join_wan) field instead. This field will be removed in a future version of Consul.**
  This field is an alias of `retry_join_wan`.

## Log Parameters

- `log_file` Equivalent to the [`-log-file` command-line flag](/consul/docs/agent/config/cli-flags#_log_file).

- `log_rotate_duration` Equivalent to the [`-log-rotate-duration` command-line flag](/consul/docs/agent/config/cli-flags#_log_rotate_duration).

- `log_rotate_bytes` Equivalent to the [`-log-rotate-bytes` command-line flag](/consul/docs/agent/config/cli-flags#_log_rotate_bytes).

- `log_rotate_max_files` Equivalent to the [`-log-rotate-max-files` command-line flag](/consul/docs/agent/config/cli-flags#_log_rotate_max_files).

- `log_level` Equivalent to the [`-log-level` command-line flag](/consul/docs/agent/config/cli-flags#_log_level).

- `log_json` Equivalent to the [`-log-json` command-line flag](/consul/docs/agent/config/cli-flags#_log_json).

- `enable_syslog` Equivalent to the [`-syslog` command-line flag](/consul/docs/agent/config/cli-flags#_syslog).

- `syslog_facility` When [`enable_syslog`](#enable_syslog)
  is provided, this controls to which facility messages are sent. By default, `LOCAL0`
  will be used.

## Node Parameters

- `node_id` Equivalent to the [`-node-id` command-line flag](/consul/docs/agent/config/cli-flags#_node_id).

- `node_name` Equivalent to the [`-node` command-line flag](/consul/docs/agent/config/cli-flags#_node).

- `node_meta` Available in Consul 0.7.3 and later, This object allows associating arbitrary metadata key/value pairs with the local node, which can then be used for filtering results from certain catalog endpoints. See the [`-node-meta` command-line flag](/consul/docs/agent/config/cli-flags#_node_meta) for more information.

  <CodeTabs heading="Example node_meta configuration">

  ```hcl
  node_meta {
    instance_type = "t2.medium"
  }
  ```

  ```json
  {
    "node_meta": {
      "instance_type": "t2.medium"
    }
  }
  ```

  </CodeTabs>

- `disable_host_node_id` Equivalent to the [`-disable-host-node-id` command-line flag](/consul/docs/agent/config/cli-flags#_disable_host_node_id).

## Raft Parameters

- `raft_boltdb` ((#raft_boltdb)) **These fields are deprecated in Consul v1.15.0.
  Use [`raft_logstore`](#raft_logstore) instead.** This is a nested
  object that allows configuring options for Raft's BoltDB-based log store.

  - `NoFreelistSync` **This field is deprecated in Consul v1.15.0. Use the
    [`raft_logstore.boltdb.no_freelist_sync`](#raft_logstore_boltdb_no_freelist_sync) field
    instead.** Setting this to `true` disables syncing the BoltDB freelist
    to disk within the raft.db file. Not syncing the freelist to disk
    reduces disk IO required for write operations at the expense of potentially
    increasing start up time due to needing to scan the db to discover where the
    free space resides within the file.

- `raft_logstore` ((#raft_logstore)) This is a nested object that allows
  configuring options for Raft's LogStore component which is used to persist
  logs and crucial Raft state on disk during writes. This was added in Consul
  v1.15.0.

  - `backend` ((#raft_logstore_backend)) Specifies which storage
    engine to use to persist logs. Valid options are `boltdb` or `wal`. Default
    is `boltdb`. The `wal` option specifies an experimental backend that
    should be used with caution. Refer to
    [Experimental WAL LogStore backend](/consul/docs/agent/wal-logstore)
    for more information.

  - `disable_log_cache` ((#raft_logstore_disable_log_cache)) Disables the in-memory cache for recent logs. We recommend using it for performance testing purposes, as no significant improvement has been measured when the cache is disabled. While the in-memory log cache theoretically prevents disk reads for recent logs, recent logs are also stored in the OS page cache, which does not slow either the `boltdb` or `wal` backend's ability to read them.

  - `verification` ((#raft_logstore_verification)) This is a nested object that
    allows configuring the online verification of the LogStore. Verification
    provides additional assurances that LogStore backends are correctly storing
    data. It imposes low overhead on servers and is safe to run in
    production. It is most useful when evaluating a new backend
    implementation.

    Verification must be enabled on the leader to have any effect and can be
    used with any backend. When enabled, the leader periodically writes a
    special "checkpoint" log message that includes the checksums of all log entries
    written to Raft since the last checkpoint. Followers that have verification
    enabled run a background task for each checkpoint that reads all logs
    directly from the LogStore and then recomputes the checksum. A report is output
    as an INFO level log for each checkpoint.

    Checksum failure should never happen and indicate unrecoverable corruption
    on that server. The only correct response is to stop the server, remove its
    data directory, and restart so it can be caught back up with a correct
    server again. Please report verification failures including details about
    your hardware and workload via GitHub issues. Refer to
    [Experimental WAL LogStore backend](/consul/docs/agent/wal-logstore)
    for more information.

    - `enabled` ((#raft_logstore_verification_enabled)) - Set to `true` to
    allow this Consul server to write and verify log verification checkpoints
    when elected leader.

    - `interval` ((#raft_logstore_verification_interval)) - Specifies the time
      interval between checkpoints. There is no default value. You must
      configure the `interval` and set [`enabled`](#raft_logstore_verification_enabled)
      to `true` to correctly enable intervals. We recommend using an interval
      between `30s` and `5m`. The performance overhead is insignificant when the
      interval is set to `5m` or less.

  - `boltdb` ((#raft_logstore_boltdb)) - Object that configures options for
    Raft's `boltdb` backend. It has no effect if the `backend` is not `boltdb`.

    - `no_freelist_sync` ((#raft_logstore_boltdb_no_freelist_sync)) - Set to
    `true` to disable storing BoltDB's freelist to disk within the
    `raft.db` file. Disabling freelist syncs reduces the disk IO required
    for write operations, but could potentially increase start up time
    because Consul must scan the database to find free space
    within the file.

  - - `wal` ((#raft_logstore_wal)) - Object that configures the `wal` backend.
    Refer to [Experimental WAL LogStore backend](/consul/docs/agent/wal-logstore)
    for more information.

    - `segment_size_mb` ((#raft_logstore_wal_segment_size_mb)) - Integer value
      that represents the target size in MB for each segment file before
      rolling to a new segment. The default value is `64` and is suitable for
      most deployments. While a smaller value may use less disk space because you
      can reclaim space by deleting old segments sooner, the smaller segment that results
      may affect performance because safely rotating to a new file more
      frequently can impact tail latencies. Larger values are unlikely
      to improve performance significantly. We recommend using this
      configuration for performance testing purposes.

- `raft_protocol` ((#raft_protocol)) Equivalent to the [`-raft-protocol`
  command-line flag](/consul/docs/agent/config/cli-flags#_raft_protocol).

- `raft_snapshot_threshold` ((#\_raft_snapshot_threshold)) This controls the
  minimum number of raft commit entries between snapshots that are saved to
  disk. This is a low-level parameter that should rarely need to be changed.
  Very busy clusters experiencing excessive disk IO may increase this value to
  reduce disk IO, and minimize the chances of all servers taking snapshots at
  the same time. Increasing this trades off disk IO for disk space since the log
  will grow much larger and the space in the raft.db file can't be reclaimed
  till the next snapshot. Servers may take longer to recover from crashes or
  failover if this is increased significantly as more logs will need to be
  replayed. In Consul 1.1.0 and later this defaults to 16384, and in prior
  versions it was set to 8192.

  Since Consul 1.10.0 this can be reloaded using `consul reload` or sending the
  server a `SIGHUP` to allow tuning snapshot activity without a rolling restart
  in emergencies.

- `raft_snapshot_interval` ((#\_raft_snapshot_interval)) This controls how often
  servers check if they need to save a snapshot to disk. This is a low-level
  parameter that should rarely need to be changed. Very busy clusters
  experiencing excessive disk IO may increase this value to reduce disk IO, and
  minimize the chances of all servers taking snapshots at the same time.
  Increasing this trades off disk IO for disk space since the log will grow much
  larger and the space in the raft.db file can't be reclaimed till the next
  snapshot. Servers may take longer to recover from crashes or failover if this
  is increased significantly as more logs will need to be replayed. In Consul
  1.1.0 and later this defaults to `30s`, and in prior versions it was set to
  `5s`.

  Since Consul 1.10.0 this can be reloaded using `consul reload` or sending the
  server a `SIGHUP` to allow tuning snapshot activity without a rolling restart
  in emergencies.

- `raft_trailing_logs` - This controls how many log entries are left in the log
  store on disk after a snapshot is made. This should only be adjusted when
  followers cannot catch up to the leader due to a very large snapshot size
  and high write throughput causing log truncation before an snapshot can be
  fully installed on a follower. If you need to use this to recover a cluster,
  consider reducing write throughput or the amount of data stored on Consul as
  it is likely under a load it is not designed to handle. The default value is
  10000 which is suitable for all normal workloads. Added in Consul 1.5.3.

  Since Consul 1.10.0 this can be reloaded using `consul reload` or sending the
  server a `SIGHUP` to allow recovery without downtime when followers can't keep
  up.

## Serf Parameters

- `serf_lan` ((#serf_lan_bind)) Equivalent to the [`-serf-lan-bind` command-line flag](/consul/docs/agent/config/cli-flags#_serf_lan_bind).
  This is an IP address, not to be confused with [`ports.serf_lan`](#serf_lan_port).

- `serf_lan_allowed_cidrs` ((#serf_lan_allowed_cidrs)) Equivalent to the [`-serf-lan-allowed-cidrs` command-line flag](/consul/docs/agent/config/cli-flags#_serf_lan_allowed_cidrs).

- `serf_wan` ((#serf_wan_bind)) Equivalent to the [`-serf-wan-bind` command-line flag](/consul/docs/agent/config/cli-flags#_serf_wan_bind).

- `serf_wan_allowed_cidrs` ((#serf_wan_allowed_cidrs)) Equivalent to the [`-serf-wan-allowed-cidrs` command-line flag](/consul/docs/agent/config/cli-flags#_serf_wan_allowed_cidrs).

## Telemetry Parameters

- `telemetry` This is a nested object that configures where
  Consul sends its runtime telemetry, and contains the following keys:

  - `circonus_api_token` ((#telemetry-circonus_api_token)) A valid API
    Token used to create/manage check. If provided, metric management is
    enabled.

  - `circonus_api_app` ((#telemetry-circonus_api_app)) A valid app name
    associated with the API token. By default, this is set to "consul".

  - `circonus_api_url` ((#telemetry-circonus_api_url))
    The base URL to use for contacting the Circonus API. By default, this is set
    to "https://api.circonus.com/v2".

  - `circonus_submission_interval` ((#telemetry-circonus_submission_interval)) The interval at which metrics are submitted to Circonus. By default, this is set to "10s" (ten seconds).

  - `circonus_submission_url` ((#telemetry-circonus_submission_url))
    The `check.config.submission_url` field, of a Check API object, from a previously
    created HTTPTrap check.

  - `circonus_check_id` ((#telemetry-circonus_check_id))
    The Check ID (not **check bundle**) from a previously created HTTPTrap check.
    The numeric portion of the `check._cid` field in the Check API object.

  - `circonus_check_force_metric_activation` ((#telemetry-circonus_check_force_metric_activation)) Force activation of metrics which already exist and are not currently active.
    If check management is enabled, the default behavior is to add new metrics as
    they are encountered. If the metric already exists in the check, it will **not**
    be activated. This setting overrides that behavior. By default, this is set to
    false.

  - `circonus_check_instance_id` ((#telemetry-circonus_check_instance_id)) Uniquely identifies the metrics coming from this **instance**. It can be used to
    maintain metric continuity with transient or ephemeral instances as they move
    around within an infrastructure. By default, this is set to hostname:application
    name (e.g. "host123:consul").

  - `circonus_check_search_tag` ((#telemetry-circonus_check_search_tag)) A special tag which, when coupled with the instance id, helps to narrow down
    the search results when neither a Submission URL or Check ID is provided. By
    default, this is set to service:application name (e.g. "service:consul").

  - `circonus_check_display_name` ((#telemetry-circonus_check_display_name)) Specifies a name to give a check when it is created. This name is displayed in
    the Circonus UI Checks list. Available in Consul 0.7.2 and later.

  - `circonus_check_tags` ((#telemetry-circonus_check_tags))
    Comma separated list of additional tags to add to a check when it is created.
    Available in Consul 0.7.2 and later.

  - `circonus_broker_id` ((#telemetry-circonus_broker_id))
    The ID of a specific Circonus Broker to use when creating a new check. The numeric
    portion of `broker._cid` field in a Broker API object. If metric management is
    enabled and neither a Submission URL nor Check ID is provided, an attempt will
    be made to search for an existing check using Instance ID and Search Tag. If
    one is not found, a new HTTPTrap check will be created. By default, this is not
    used and a random Enterprise Broker is selected, or the default Circonus Public
    Broker.

  - `circonus_broker_select_tag` ((#telemetry-circonus_broker_select_tag)) A special tag which will be used to select a Circonus Broker when a Broker ID
    is not provided. The best use of this is to as a hint for which broker should
    be used based on **where** this particular instance is running (e.g. a specific
    geo location or datacenter, dc:sfo). By default, this is left blank and not used.

  - `disable_hostname` ((#telemetry-disable_hostname))
    Set to `true` to stop prepending the machine's hostname to gauge-type metrics. Default is `false`.

  - `dogstatsd_addr` ((#telemetry-dogstatsd_addr)) This provides the address
    of a DogStatsD instance in the format `host:port`. DogStatsD is a protocol-compatible
    flavor of statsd, with the added ability to decorate metrics with tags and event
    information. If provided, Consul will send various telemetry information to that
    instance for aggregation. This can be used to capture runtime information.

  - `dogstatsd_tags` ((#telemetry-dogstatsd_tags)) This provides a list
    of global tags that will be added to all telemetry packets sent to DogStatsD.
    It is a list of strings, where each string looks like "my_tag_name:my_tag_value".

  - `enable_host_metrics` ((#telemetry-enable_host_metrics))
    This enables reporting of host metrics about system resources, defaults to false.

  - `filter_default` ((#telemetry-filter_default))
    This controls whether to allow metrics that have not been specified by the filter.
    Defaults to `true`, which will allow all metrics when no filters are provided.
    When set to `false` with no filters, no metrics will be sent.

  - `metrics_prefix` ((#telemetry-metrics_prefix))
    The prefix used while writing all telemetry data. By default, this is set to
    "consul". This was added in Consul 1.0. For previous versions of Consul, use
    the config option `statsite_prefix` in this same structure. This was renamed
    in Consul 1.0 since this prefix applied to all telemetry providers, not just
    statsite.

  - `prefix_filter` ((#telemetry-prefix_filter))
    This is a list of filter rules to apply for allowing/blocking metrics by
    prefix in the following format:

    <CodeTabs heading="Example prefix_filter configuration">

    ```hcl
    telemetry {
      prefix_filter = ["+consul.raft.apply", "-consul.http", "+consul.http.GET"]
    }
    ```

    ```json
    {
      "telemetry": {
        "prefix_filter": [
          "+consul.raft.apply",
          "-consul.http",
          "+consul.http.GET"
        ]
      }
    }
    ```

    </CodeTabs>

    A leading "**+**" will enable any metrics with the given prefix, and a leading "**-**" will block them. If there is overlap between two rules, the more specific rule will take precedence. Blocking will take priority if the same prefix is listed multiple times.

  - `prometheus_retention_time` ((#telemetry-prometheus_retention_time)) If the value is greater than `0s` (the default), this enables [Prometheus](https://prometheus.io/)
    export of metrics. The duration can be expressed using the duration semantics
    and will aggregates all counters for the duration specified (it might have an
    impact on Consul's memory usage). A good value for this parameter is at least
    2 times the interval of scrape of Prometheus, but you might also put a very high
    retention time such as a few days (for instance 744h to enable retention to 31
    days). Fetching the metrics using prometheus can then be performed using the
    [`/v1/agent/metrics?format=prometheus`](/consul/api-docs/agent#view-metrics) endpoint.
    The format is compatible natively with prometheus. When running in this mode,
    it is recommended to also enable the option [`disable_hostname`](#telemetry-disable_hostname)
    to avoid having prefixed metrics with hostname. Consul does not use the default
    Prometheus path, so Prometheus must be configured as follows. Note that using
    `?format=prometheus` in the path won't work as `?` will be escaped, so it must be
    specified as a parameter.

    <CodeBlockConfig heading="Example Prometheus configuration">

    ```yaml
    metrics_path: '/v1/agent/metrics'
    params:
      format: ['prometheus']
    ```

    </CodeBlockConfig>

  - `statsd_address` ((#telemetry-statsd_address)) This provides the address
    of a statsd instance in the format `host:port`. If provided, Consul will send
    various telemetry information to that instance for aggregation. This can be used
    to capture runtime information. This sends UDP packets only and can be used with
    statsd or statsite.

  - `statsite_address` ((#telemetry-statsite_address)) This provides the
    address of a statsite instance in the format `host:port`. If provided, Consul
    will stream various telemetry information to that instance for aggregation. This
    can be used to capture runtime information. This streams via TCP and can only
    be used with statsite.

## UI Parameters

- `ui` - **This field is deprecated in Consul 1.9.0. See the [`ui_config.enabled`](#ui_config_enabled) field instead.**
  Equivalent to the [`-ui`](/consul/docs/agent/config/cli-flags#_ui) command-line flag.

- `ui_config` - This object allows a number of sub-keys to be set which controls
  the display or features available in the UI. Configuring the UI with this
  stanza was added in Consul 1.9.0.

  The following sub-keys are available:

  - `enabled` ((#ui_config_enabled)) - This enables the service of the web UI
    from this agent. Boolean value, defaults to false. In `-dev` mode this
    defaults to true. Replaces `ui` from before 1.9.0. Equivalent to the
    [`-ui`](/consul/docs/agent/config/cli-flags#_ui) command-line flag.

  - `dir` ((#ui_config_dir)) - This specifies that the web UI should be served
    from an external dir rather than the build in one. This allows for
    customization or development. Replaces `ui_dir` from before 1.9.0.
    Equivalent to the [`-ui-dir`](/consul/docs/agent/config/cli-flags#_ui_dir) command-line flag.

  - `content_path` ((#ui_config_content_path)) - This specifies the HTTP path
    that the web UI should be served from. Defaults to `/ui/`. Equivalent to the
    [`-ui-content-path`](/consul/docs/agent/config/cli-flags#_ui_content_path) flag.

  - `metrics_provider` ((#ui_config_metrics_provider)) - Specifies a named
    metrics provider implementation the UI should use to fetch service metrics.
    By default metrics are disabled. Consul 1.9.0 includes a built-in provider
    named `prometheus` that can be enabled explicitly here. It also requires the
    `metrics_proxy` to be configured below and direct queries to a Prometheus
    instance that has Envoy metrics for all services in the datacenter.

  - `metrics_provider_files` ((#ui_config_metrics_provider_files)) - An optional array
    of absolute paths to javascript files on the Agent's disk which will be
    served as part of the UI. These files should contain metrics provider
    implementations and registration enabling UI metric queries to be customized
    or implemented for an alternative time-series backend.

    ~> **Security Note:** These javascript files are included in the UI with no
    further validation or sand-boxing. By configuring them here the operator is
    fully trusting anyone able to write to them as well as the original authors
    not to include malicious code in the UI being served.

  - `metrics_provider_options_json` ((#ui_config_metrics_provider_options_json)) -
    This is an optional raw JSON object as a string which is passed to the
    provider implementation's `init` method at startup to allow arbitrary
    configuration to be passed through.

  - `metrics_proxy` ((#ui_config_metrics_proxy)) - This object configures an
    internal agent API endpoint that will proxy GET requests to a metrics
    backend to allow querying metrics data in the UI. This simplifies deployment
    where the metrics backend is not exposed externally to UI users' browsers.
    It may also be used to augment requests with API credentials to allow
    serving graphs to UI users without them needing individual access tokens for
    the metrics backend.

    ~> **Security Note:** Exposing your metrics backend via Consul in this way
    should be carefully considered in production. As Consul doesn't understand
    the requests, it can't limit access to only specific resources. For example
    **this might make it possible for a malicious user on the network to query
    for arbitrary metrics about any server or workload in your infrastructure,
    or overload the metrics infrastructure with queries**. See [Metrics Proxy
    Security](/consul/docs/connect/observability/ui-visualization#metrics-proxy-security)
    for more details.

    The following sub-keys are available:

    - `base_url` ((#ui_config_metrics_provider_base_url)) - This is required to
      enable the proxy. It should be set to the base URL that the Consul agent
      should proxy requests for metrics too. For example a value of
      `http://prometheus-server` would target a Prometheus instance with local
      DNS name "prometheus-server" on port 80. This may include a path prefix
      which will then not be necessary in provider requests to the backend and
      the proxy will prevent any access to paths without that prefix on the
      backend.

    - `path_allowlist` ((#ui_config_metrics_provider_path_allowlist)) - This
      specifies the paths that may be proxies to when appended to the
      `base_url`. It defaults to `["/api/v1/query_range", "/api/v1/query"]`
      which are the endpoints required for the built-in Prometheus provider. If
      a [custom
      provider](/consul/docs/connect/observability/ui-visualization#custom-metrics-providers)
      is used that requires the metrics proxy, the correct allowlist must be
      specified to enable proxying to necessary endpoints. See [Path
      Allowlist](/consul/docs/connect/observability/ui-visualization#path-allowlist)
      for more information.

    - `add_headers` ((#ui_config_metrics_proxy_add_headers)) - This is an
      optional list if headers to add to requests that are proxied to the
      metrics backend. It may be used to inject Authorization tokens within the
      agent without exposing those to UI users.

      Each item in the list is an object with the following keys:

      - `name` ((#ui_config_metrics_proxy_add_headers_name)) - Specifies the
        HTTP header name to inject into proxied requests.

      - `value` ((#ui_config_metrics_proxy_add_headers_value)) - Specifies the
        value in inject into proxied requests.

  - `dashboard_url_templates` ((#ui_config_dashboard_url_templates)) - This map
    specifies URL templates that may be used to render links to external
    dashboards in various contexts in the UI. It is a map with the name of the
    template as a key. The value is a string URL with optional placeholders.

    Each template may contain placeholders which will be substituted for the
    correct values in content when rendered in the UI. The placeholders
    available are listed for each template.

    For more information and examples see [UI
    Visualization](/consul/docs/connect/observability/ui-visualization#configuring-dashboard-urls)

    The following named templates are defined:

    - `service` ((#ui_config_dashboard_url_templates_service)) - This is the URL
      to use when linking to the dashboard for a specific service. It is shown
      as part of the [Topology
      Visualization](/consul/docs/connect/observability/ui-visualization).

      The placeholders available are:

      - `{{Service.Name}}` - Replaced with the current service's name.
      - `{{Service.Namespace}}` - Replaced with the current service's namespace or empty if namespaces are not enabled.
      - `{{Service.Partition}}` - Replaced with the current service's admin
        partition or empty if admin partitions are not enabled.
      - `{{Datacenter}}` - Replaced with the current service's datacenter.

- `ui_dir` - **This field is deprecated in Consul 1.9.0. See the [`ui_config.dir`](#ui_config_dir) field instead.**
  Equivalent to the [`-ui-dir`](/consul/docs/agent/config/cli-flags#_ui_dir) command-line
  flag. This configuration key is not required as of Consul version 0.7.0 and later.
  Specifying this configuration key will enable the web UI. There is no need to specify
  both ui-dir and ui. Specifying both will result in an error.

## TLS Configuration Reference

This section documents all of the configuration settings that apply to Agent TLS. Agent
TLS is used by the HTTP API, internal RPC, and gRPC/xDS interfaces. Some of these settings
may also be applied automatically by [auto_config](#auto_config) or [auto_encrypt](#auto_encrypt).

~> **Security Note:** The Certificate Authority (CA) configured on the internal RPC interface
(either explicitly by `tls.internal_rpc` or implicitly by `tls.defaults`) should be a private
CA, not a public one. We recommend using a dedicated CA which should not be used with any other
systems. Any certificate signed by the CA will be allowed to communicate with the cluster and a
specially crafted certificate signed by the CA can be used to gain full access to Consul.

- `tls` Added in Consul 1.12, for previous versions see
  [Deprecated Options](#tls_deprecated_options).

  - `defaults` ((#tls_defaults)) Provides default settings that will be applied
    to every interface unless explicitly overridden by `tls.grpc`, `tls.https`,
    or `tls.internal_rpc`.

    - `ca_file` ((#tls_defaults_ca_file)) This provides a file path to a
      PEM-encoded certificate authority. The certificate authority is used to
      check the authenticity of client and server connections with the
      appropriate [`verify_incoming`](#tls_defaults_verify_incoming) or
      [`verify_outgoing`](#tls_defaults_verify_outgoing) flags.

    - `ca_path` ((#tls_defaults_ca_path)) This provides a path to a directory
      of PEM-encoded certificate authority files. These certificate authorities
      are used to check the authenticity of client and server connections with
      the appropriate [`verify_incoming`](#tls_defaults_verify_incoming) or
      [`verify_outgoing`](#tls_defaults_verify_outgoing) flags.

    - `cert_file` ((#tls_defaults_cert_file)) This provides a file path to a
      PEM-encoded certificate. The certificate is provided to clients or servers
      to verify the agent's authenticity. It must be provided along with
      [`key_file`](#tls_defaults_key_file).

    - `key_file` ((#tls_defaults_key_file)) This provides a the file path to a
      PEM-encoded private key. The key is used with the certificate to verify
      the agent's authenticity. This must be provided along with
      [`cert_file`](#tls_defaults_cert_file).

    - `tls_min_version` ((#tls_defaults_tls_min_version)) This specifies the
      minimum supported version of TLS. The following values are accepted:
      * `TLSv1_0`
      * `TLSv1_1`
      * `TLSv1_2` (default)
      * `TLSv1_3`

      **WARNING: TLS 1.1 and lower are generally considered less secure and
      should not be used if possible.**

      The following values are also valid, but only when using the
      [deprecated top-level `tls_min_version` config](#tls_deprecated_options),
      and will be removed in a future release:

      * `tls10`
      * `tls11`
      * `tls12`
      * `tls13`

      A warning message will appear if a deprecated value is specified.

    - `tls_cipher_suites` ((#tls_defaults_tls_cipher_suites)) This specifies
      the list of supported ciphersuites as a comma-separated-list. Applicable
      to TLS 1.2 and below only. The list of all ciphersuites supported by Consul is
      available in [the TLS configuration source code](https://github.com/hashicorp/consul/search?q=%22var+goTLSCipherSuites%22).

      ~> **Note:** The ordering of cipher suites will not be guaranteed from
      Consul 1.11 onwards. See this [post](https://go.dev/blog/tls-cipher-suites)
      for details.

    - `verify_incoming` - ((#tls_defaults_verify_incoming)) If set to true,
      Consul requires that all incoming connections make use of TLS and that
      the client provides a certificate signed by a Certificate Authority from
      the [`ca_file`](#tls_defaults_ca_file) or [`ca_path`](#tls_defaults_ca_path).
      By default, this is false, and Consul will not enforce the use of TLS or
      verify a client's authenticity.

    - `verify_outgoing` - ((#tls_defaults_verify_outgoing)) If set to true,
      Consul requires that all outgoing connections from this agent make use
      of TLS and that the server provides a certificate that is signed by a
      Certificate Authority from the [`ca_file`](#tls_defaults_ca_file) or
      [`ca_path`](#tls_defaults_ca_path). By default, this is false, and Consul
      will not make use of TLS for outgoing connections. This applies to clients
      and servers as both will make outgoing connections. This setting does not
      apply to the gRPC interface as Consul makes no outgoing connections on this
      interface.

  - `grpc` ((#tls_grpc)) Provides settings for the gRPC/xDS interface. To enable
    the gRPC interface you must define a port via [`ports.grpc_tls`](#grpc_tls_port).

    - `ca_file` ((#tls_grpc_ca_file)) Overrides [`tls.defaults.ca_file`](#tls_defaults_ca_file).

    - `ca_path` ((#tls_grpc_ca_path)) Overrides [`tls.defaults.ca_path`](#tls_defaults_ca_path).

    - `cert_file` ((#tls_grpc_cert_file)) Overrides [`tls.defaults.cert_file`](#tls_defaults_cert_file).

    - `key_file` ((#tls_grpc_key_file)) Overrides [`tls.defaults.key_file`](#tls_defaults_key_file).

    - `tls_min_version` ((#tls_grpc_tls_min_version)) Overrides [`tls.defaults.tls_min_version`](#tls_defaults_tls_min_version).

    - `tls_cipher_suites` ((#tls_grpc_tls_cipher_suites)) Overrides [`tls.defaults.tls_cipher_suites`](#tls_defaults_tls_cipher_suites).

    - `verify_incoming` - ((#tls_grpc_verify_incoming)) Overrides [`tls.defaults.verify_incoming`](#tls_defaults_verify_incoming).

    - `use_auto_cert` - (Defaults to `false`) Enables or disables TLS on gRPC servers. Set to `true` to allow `auto_encrypt` TLS settings to apply to gRPC listeners. We recommend disabling TLS on gRPC servers if you are using `auto_encrypt` for other TLS purposes, such as enabling HTTPS.

  - `https` ((#tls_https)) Provides settings for the HTTPS interface. To enable
    the HTTPS interface you must define a port via [`ports.https`](#https_port).

    - `ca_file` ((#tls_https_ca_file)) Overrides [`tls.defaults.ca_file`](#tls_defaults_ca_file).

    - `ca_path` ((#tls_https_ca_path)) Overrides [`tls.defaults.ca_path`](#tls_defaults_ca_path).

    - `cert_file` ((#tls_https_cert_file)) Overrides [`tls.defaults.cert_file`](#tls_defaults_cert_file).

    - `key_file` ((#tls_https_key_file)) Overrides [`tls.defaults.key_file`](#tls_defaults_key_file).

    - `tls_min_version` ((#tls_https_tls_min_version)) Overrides [`tls.defaults.tls_min_version`](#tls_defaults_tls_min_version).

    - `tls_cipher_suites` ((#tls_https_tls_cipher_suites)) Overrides [`tls.defaults.tls_cipher_suites`](#tls_defaults_tls_cipher_suites).

    - `verify_incoming` - ((#tls_https_verify_incoming)) Overrides [`tls.defaults.verify_incoming`](#tls_defaults_verify_incoming).

    - `verify_outgoing` - ((#tls_https_verify_outgoing)) Overrides [`tls.defaults.verify_outgoing`](#tls_defaults_verify_outgoing).

  - `internal_rpc` ((#tls_internal_rpc)) Provides settings for the internal
    "server" RPC interface configured by [`ports.server`](#server_rpc_port).

    - `ca_file` ((#tls_internal_rpc_ca_file)) Overrides [`tls.defaults.ca_file`](#tls_defaults_ca_file).

    - `ca_path` ((#tls_internal_rpc_ca_path)) Overrides [`tls.defaults.ca_path`](#tls_defaults_ca_path).

    - `cert_file` ((#tls_internal_rpc_cert_file)) Overrides [`tls.defaults.cert_file`](#tls_defaults_cert_file).

    - `key_file` ((#tls_internal_rpc_key_file)) Overrides [`tls.defaults.key_file`](#tls_defaults_key_file).

    - `tls_min_version` ((#tls_internal_rpc_tls_min_version)) Overrides [`tls.defaults.tls_min_version`](#tls_defaults_tls_min_version).

    - `tls_cipher_suites` ((#tls_internal_rpc_tls_cipher_suites)) Overrides [`tls.defaults.tls_cipher_suites`](#tls_defaults_tls_cipher_suites).

    - `verify_incoming` - ((#tls_internal_rpc_verify_incoming)) Overrides [`tls.defaults.verify_incoming`](#tls_defaults_verify_incoming).

      ~> **Security Note:** `verify_incoming` *must* be set to true to prevent
      anyone with access to the internal RPC port from gaining full access to
      the Consul cluster.

    - `verify_outgoing` ((#tls_internal_rpc_verify_outgoing)) Overrides [`tls.defaults.verify_outgoing`](#tls_defaults_verify_outgoing).

      ~> **Security Note:** Servers that specify `verify_outgoing = true` will
      always talk to other servers over TLS, but they still _accept_ non-TLS
      connections to allow for a transition of all clients to TLS. Currently the
      only way to enforce that no client can communicate with a server unencrypted
      is to also enable `verify_incoming` which requires client certificates too.

    - `verify_server_hostname` ((#tls_internal_rpc_verify_server_hostname)) When
      set to true, Consul verifies the TLS certificate presented by the servers
      match the hostname `server.<datacenter>.<domain>`. By default this is false,
      and Consul does not verify the hostname of the certificate, only that it
      is signed by a trusted CA.

      ~> **Security Note:** `verify_server_hostname` *must* be set to true to prevent a
      compromised client from gaining full read and write access to all cluster
      data *including all ACL tokens and service mesh CA root keys*.

- `server_name` When provided, this overrides the [`node_name`](#_node)
  for the TLS certificate. It can be used to ensure that the certificate name matches
  the hostname we declare.

### Deprecated Options ((#tls_deprecated_options))

The following options were deprecated in Consul 1.12, please use the
[`tls`](#tls-1) stanza instead.

- `ca_file` See: [`tls.defaults.ca_file`](#tls_defaults_ca_file).

- `ca_path` See: [`tls.defaults.ca_path`](#tls_defaults_ca_path).

- `cert_file` See: [`tls.defaults.cert_file`](#tls_defaults_cert_file).

- `key_file` See: [`tls.defaults.key_file`](#tls_defaults_key_file).

- `tls_min_version` Added in Consul 0.7.4.
  See: [`tls.defaults.tls_min_version`](#tls_defaults_tls_min_version).

- `tls_cipher_suites` Added in Consul 0.8.2.
  See: [`tls.defaults.tls_cipher_suites`](#tls_defaults_tls_cipher_suites).

- `tls_prefer_server_cipher_suites` Added in Consul 0.8.2. This setting will
  be ignored (see [this post](https://go.dev/blog/tls-cipher-suites) for details).

- `verify_incoming` See: [`tls.defaults.verify_incoming`](#tls_defaults_verify_incoming).

- `verify_incoming_rpc` See: [`tls.internal_rpc.verify_incoming`](#tls_internal_rpc_verify_incoming).

- `verify_incoming_https` See: [`tls.https.verify_incoming`](#tls_https_verify_incoming).

- `verify_outgoing` See: [`tls.defaults.verify_outgoing`](#tls_defaults_verify_outgoing).

- `verify_server_hostname` See: [`tls.internal_rpc.verify_server_hostname`](#tls_internal_rpc_verify_server_hostname).

### Example Configuration File, with TLS

~> **Security Note:** all three verify options should be set as `true` to enable
secure mTLS communication, enabling both encryption and authentication. Failing
to set [`verify_incoming`](#tls_defaults_verify_incoming) or
[`verify_outgoing`](#tls_defaults_verify_outgoing) either in the
interface-specific stanza (e.g. `tls.internal_rpc`, `tls.https`) or in
`tls.defaults` will result in TLS not being enabled at all, even when specifying
a [`ca_file`](#tls_defaults_ca_file), [`cert_file`](#tls_defaults_cert_file),
and [`key_file`](#tls_defaults_key_file).

See, especially, the use of the `ports` setting highlighted below.

<CodeTabs heading="Example configuration with TLS">

<CodeBlockConfig lineNumbers highlight="10-12">

```hcl
datacenter = "east-aws"
data_dir = "/opt/consul"
log_level = "INFO"
node_name = "foobar"
server = true

addresses = {
  https = "0.0.0.0"
}
ports {
  https = 8501
}

tls {
  defaults {
    key_file = "/etc/pki/tls/private/my.key"
    cert_file = "/etc/pki/tls/certs/my.crt"
    ca_file = "/etc/pki/tls/certs/ca-bundle.crt"
    verify_incoming = true
    verify_outgoing = true
  }

  internal_rpc {
    verify_server_hostname = true
  }
}
```

</CodeBlockConfig>

<CodeBlockConfig lineNumbers highlight="10-12">

```json
{
  "datacenter": "east-aws",
  "data_dir": "/opt/consul",
  "log_level": "INFO",
  "node_name": "foobar",
  "server": true,
  "addresses": {
    "https": "0.0.0.0"
  },
  "ports": {
    "https": 8501
  },
  "tls": {
    "defaults": {
      "key_file": "/etc/pki/tls/private/my.key",
      "cert_file": "/etc/pki/tls/certs/my.crt",
      "ca_file": "/etc/pki/tls/certs/ca-bundle.crt",
      "verify_incoming": true,
      "verify_outgoing": true
    },
    "internal_rpc": {
      "verify_server_hostname": true
    }
  }
}
```

</CodeBlockConfig>

</CodeTabs>

Consul will not enable TLS for the HTTP or gRPC API unless the `https` port has
been assigned a port number `> 0`. We recommend using `8501` for `https` as this
default will automatically work with some tooling.

## xDS Server Parameters

- `xds`: This object allows you to configure the behavior of Consul's
[xDS protocol](https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol)
server.

  - `update_max_per_second`: Specifies the number of proxy configuration updates across all connected xDS streams that are allowed per second. This configuration prevents updates to global resources, such as wildcard intentions, from consuming system resources at the expense of other processes, such as Raft and Gossip, which could cause general cluster instability.

    The default value is `250`. It is based on a load test of 5,000 streams connected to a single server with two CPU cores.

    If necessary, you can lower or increase the limit without a rolling restart by using the `consul reload` command or by sending the server a `SIGHUP`.
