237 lines
9.3 KiB
Plaintext
237 lines
9.3 KiB
Plaintext
---
|
|
layout: docs
|
|
page_title: Consul Enterprise Network Segments
|
|
description: |-
|
|
Consul Enterprise enables you create separate LAN gossip pools within one
|
|
cluster to segment network groups.
|
|
---
|
|
|
|
# Network Segments
|
|
|
|
<EnterpriseAlert>
|
|
This feature requires{' '}
|
|
<a href="https://www.hashicorp.com/products/consul/">Consul Enterprise</a>{' '}
|
|
version 0.9.3+ with the Global Visibility, Routing, and Scale module.
|
|
</EnterpriseAlert>
|
|
|
|
Consul requires full connectivity between all agents (servers and clients) in a
|
|
[datacenter](/docs/agent/options#_datacenter) within a given
|
|
LAN gossip pool. By default, all Consul agents will be a part of one shared Serf LAN
|
|
gossip pool known as the `<default>` network segment, thus requiring full mesh
|
|
connectivity within the datacenter.
|
|
|
|
|
|
|
|
In some environments, full connectivity between all agents is not possible—known as a
|
|
"segmented network". This is usually the result of business policies enforced through
|
|
network rules or firewalls. To use Consul in a segmented network, you must break up
|
|
the LAN gossip pool along network communication boundaries into separate "network
|
|
segments". Network segments are isolated LAN gossip pools that only require full
|
|
connectivity between agent members on the same segment.
|
|
|
|
|
|
|
|
To get started with network segments you can review the tutorial on HashiCorp
|
|
Learn for [Network Segments](https://learn.hashicorp.com/tutorials/consul/network-partition-datacenters).
|
|
|
|
-> **Info:** Network segments enable you to operate a Consul datacenter without full
|
|
mesh (LAN) connectivity between agents. To federate multiple Consul datacenters
|
|
without full mesh (WAN) connectivity between all server agents in all datacenters,
|
|
use [Network Areas (Enterprise)](/docs/enterprise/federation).
|
|
|
|
# Consul Networking Models
|
|
|
|
To help set context for this feature, it is useful to understand the various
|
|
Consul networking models and their capabilities.
|
|
|
|
**Cluster:** A set of Consul servers forming a Raft quorum along with a
|
|
collection of Consul clients, all set to the same
|
|
[datacenter](/docs/agent/options#_datacenter), and joined together to form
|
|
what we will call a "local cluster". Consul clients discover the Consul servers
|
|
in their local cluster through the gossip mechanism and make RPC requests to
|
|
them. LAN Gossip (OSS) is an open intra-cluster networking model, and Network
|
|
Segments (Enterprise) creates multiple segments within one cluster.
|
|
|
|
**Federated Cluster:** A cluster of clusters with a Consul server group per
|
|
cluster each set per "datacenter". These Consul servers are federated together
|
|
over the WAN. Consul clients make use of resources in federated clusters by
|
|
forwarding RPCs through the Consul servers in their local cluster, but they
|
|
never interact with remote Consul servers directly. There are currently two
|
|
inter-cluster network models which can be viewed on HashiCorp Learn:
|
|
[WAN gossip (OSS)](https://learn.hashicorp.com/tutorials/consul/federarion-gossip-wan)
|
|
and [Network Areas (Enterprise)](https://learn.hashicorp.com/tutorials/consul/federation-network-areas).
|
|
|
|
**LAN Gossip Pool**: A set of Consul agents that have full mesh connectivity
|
|
among themselves, and use Serf to maintain a shared view of the members of the
|
|
pool for different purposes, like finding a Consul server in a local cluster,
|
|
or finding servers in a remote cluster. A **segmented** LAN Gossip Pool limits a
|
|
group of agents to only connect with the agents in its segment.
|
|
|
|
# Network Segments Configuration
|
|
|
|
## Server Configuration
|
|
|
|
Server agents are members of all segments. The datacenter includes a `<default>`
|
|
segment, as well as additional segments defined in the
|
|
[`segments`](/docs/agent/options#segments) server agent configuration option.
|
|
Each additional segment is defined by:
|
|
|
|
- a non-empty name
|
|
- a unique port
|
|
- optionally, a custom bind and advertise address for the additional segment's
|
|
Serf LAN listener on the server
|
|
|
|
~> **Note:** Prior to Consul 1.7.3, a Consul server agent configured with too
|
|
many network segments may not be able to start due to [limitations](https://learn.hashicorp.com/tutorials/consul/network-partition-datacenters#network-segments-limitations)
|
|
in Serf.
|
|
|
|
### Example Server Configuration
|
|
|
|
The following server agent configuration will create two user-defined network
|
|
segments: `alpha` and `beta`.
|
|
|
|
<CodeTabs heading="Example network segments configuration for server agents">
|
|
|
|
```hcl
|
|
segments = [
|
|
{
|
|
name = "alpha"
|
|
bind = "{{GetPrivateIP}}"
|
|
advertise = "{{GetPrivateIP}}"
|
|
port = 8303
|
|
},
|
|
{
|
|
name = "beta"
|
|
bind = "{{GetPrivateIP}}"
|
|
advertise = "{{GetPrivateIP}}"
|
|
port = 8304
|
|
}
|
|
]
|
|
```
|
|
|
|
```json
|
|
{
|
|
"segments": [
|
|
{
|
|
"name": "alpha",
|
|
"bind": "{{GetPrivateIP}}",
|
|
"advertise": "{{GetPrivateIP}}",
|
|
"port": 8303
|
|
},
|
|
{
|
|
"name": "beta",
|
|
"bind": "{{GetPrivateIP}}",
|
|
"advertise": "{{GetPrivateIP}}",
|
|
"port": 8304
|
|
}
|
|
]
|
|
}
|
|
```
|
|
|
|
</CodeTabs>
|
|
|
|
The server [agent configuration](/docs/agent/options) options relevant to network
|
|
segments are:
|
|
|
|
- [`ports.serf_lan`](/docs/agent/options#serf_lan_port): The Serf LAN port on this server
|
|
for the `<default>` network segment's gossip pool.
|
|
- [`segments`](/docs/agent/options#segments): A list of user-defined network segments
|
|
on this server, including their names and Serf LAN ports.
|
|
|
|
## Client Configuration
|
|
|
|
Each client agent can only be a member of one segment at a time. This will be the
|
|
`<default>` segment unless otherwise specified in the agent's
|
|
[`segment`](/docs/agent/options#_segment) agent configuration option.
|
|
|
|
### Join a Client to a Segment ((#join_a_client_to_a_segment))
|
|
|
|
For a client agent to [join](/commands/join) the Consul
|
|
datacenter, it must connect to another agent (client or server) within its
|
|
configured segment.
|
|
|
|
<Tabs>
|
|
<Tab heading="Join via another client">
|
|
|
|
Clients A and B specify the same segment S. Client B is already joined to the segment S
|
|
LAN gossip pool. Client A wants to join via Client B. In order to do so, Client A
|
|
must connect to Client B's configured [Serf LAN port](/docs/agent/options#serf_lan_port).
|
|
|
|
</Tab>
|
|
<Tab heading="Join via a server">
|
|
|
|
Client A specifies segment S and wants to join the segment S gossip pool via Server 1.
|
|
In order to do so, Client A must connect to Server 1's configured [Serf LAN port
|
|
for segment S](/docs/agent/options#segment_port).
|
|
|
|
</Tab>
|
|
</Tabs>
|
|
|
|
There are several methods to specify the port used by the join operation, listed in order
|
|
of precedence:
|
|
|
|
1. **Specify an explicit port in the join address**. This can be done at the CLI when starting
|
|
the agent (e.g., `consul agent -retry-join "client-b-address:8303"`), or in the agent's
|
|
configuration using the [retry-join option](/docs/agent/options#retry_join). This method
|
|
is not compatible with [cloud auto-join](/docs/install/cloud-auto-join#auto-join-with-network-segments).
|
|
|
|
2. **Specify an alternate Serf LAN port for the agent**. This can be done at the CLI when starting
|
|
the agent (e.g., `consul agent -retry-join "client-b-address" -serf-lan-port 8303`), or in
|
|
the agent's configuration using the [serf_lan](/docs/agent/options#serf_lan_port) option.
|
|
When a Serf LAN port is not explicitly specified in the join address, the agent will attempt to
|
|
join the target host at the Serf LAN port specified in CLI or agent configuration.
|
|
|
|
3. **Use the default Serf LAN port (8301)**. The agent will attempt to join the target host
|
|
on port 8301.
|
|
|
|
-> Agents within a segment can use different port numbers for their Serf LAN port.
|
|
For example, on the `<default>` segment, Server S can use port 8301, Client A
|
|
can use 8303, and Client B can use 8304. However, if an agent wishes to join a
|
|
segment via an agent that uses a different port number, the target agent's Serf LAN
|
|
port must be specified in the join address (method 1 above).
|
|
|
|
### Example Client Configuration
|
|
|
|
The following client agent configuration will cause the agent to:
|
|
|
|
- Open a Serf LAN listener port on 8303.
|
|
- Attempt to join the cluster via servers on port 8303 (since an alternate port is not
|
|
specified in the `retry_join` addresses).
|
|
|
|
<CodeTabs heading="Example network segment configuration for client agents">
|
|
|
|
```hcl
|
|
node_name = "consul-client1"
|
|
retry_join = ["consul-server1", "consul-server2", "consul-server3"]
|
|
segment = "alpha"
|
|
ports = {
|
|
serf_lan = 8303
|
|
}
|
|
```
|
|
|
|
```json
|
|
{
|
|
"node_name": "consul-client1",
|
|
"retry_join": ["consul-server1", "consul-server2", "consul-server3"],
|
|
"segment": "alpha",
|
|
"ports": {
|
|
"serf_lan": 8303
|
|
}
|
|
}
|
|
```
|
|
|
|
</CodeTabs>
|
|
|
|
The client [agent configuration](/docs/agent/options) options relevant to network
|
|
segments are:
|
|
|
|
- [`segment`](/docs/agent/options#segment-2): The name of the network segment this
|
|
client agent belongs to.
|
|
- [`ports.serf_lan`](/docs/agent/options#serf_lan_port):
|
|
Serf LAN port for the above segment on this client. This is not required
|
|
to match the configured Serf LAN port for other agents on this segment.
|
|
- [`retry_join`](/docs/agent/options#retry_join) or
|
|
[`start_join`](/docs/agent/options#start_join): A list of agent addresses to join
|
|
when starting. Ensure the correct Serf LAN port for this segment is used when joining
|
|
the LAN gossip pool using one of the [available configuration methods](#join_a_client_to_a_segment).
|