264 lines
9.1 KiB
Plaintext
264 lines
9.1 KiB
Plaintext
---
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layout: intro
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page_title: Consul Connect
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description: >-
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Connect is a feature of Consul that provides service-to-service connection
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authorization and encryption using mutual TLS. This ensures that all service
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communication in your datacenter is encrypted and that the rules of what
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services can communicate is centrally managed with Consul.
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---
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# Connect
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We've now registered our first service with Consul and we've shown how you
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can use the HTTP API or DNS interface to query the address and directly connect
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to that service. Consul also provides a feature called **Connect** for
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automatically connecting via an encrypted TLS connection and authorizing
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which services are allowed to connect to each other.
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Applications do not need to be modified at all to use Connect.
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[Sidecar proxies](/docs/connect/proxies) can be used
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to automatically establish TLS connections for inbound and outbound connections
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without being aware of Connect at all. Applications may also
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[natively integrate with Connect](/docs/connect/native)
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for optimal performance and security.
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-> **Security note:** The getting started guide will show Connect features and
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focus on ease of use with a dev-mode agent. We will _not setup_ Connect in a
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production-recommended secure way. Please read the [Connect production
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guide](/docs/guides/connect-production) to understand the tradeoffs.
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## Starting a Connect-unaware Service
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Let's begin by starting a service that is unaware of Connect. To keep it simple,
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let's just use `socat` to start a basic echo service. This service will accept
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TCP connections and echo back any data sent to it. If `socat` isn't installed on
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your machine, it should be easily available via a package manager.
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```shell-session
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$ socat -v tcp-l:8181,fork exec:"/bin/cat"
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```
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You can verify it is working by using `nc` to connect directly to it. Once
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connected, type some text and press enter. The text you typed should be
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echoed back:
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```shell-session
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$ nc 127.0.0.1 8181
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hello
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hello
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echo
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echo
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```
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`socat` is a decades-old Unix utility and our process is configured to
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only accept a basic TCP connection. It has no concept of encryption, the
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TLS protocol, etc. This can be representative of an existing service in
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your datacenter such as a database, backend web service, etc.
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## Registering the Service with Consul and Connect
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Next, let's register the service with Consul. We'll do this by writing
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a new service definition. This is the same as the previous step in the
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getting started guide, except this time we'll also configure Connect.
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```shell-session
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$ cat <<EOF | sudo tee /etc/consul.d/socat.json
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{
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"service": {
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"name": "socat",
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"port": 8181,
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"connect": { "sidecar_service": {} }
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}
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}
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EOF
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```
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After saving this, run `consul reload` or send a `SIGHUP` signal to Consul
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so it reads the new configuration.
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Notice the only difference is the line starting with `"connect"`. The existence
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of this empty configuration notifies Consul to register a sidecar proxy for this
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process. The proxy process represents that specific service. It accepts inbound
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connections on a dynamically allocated port, verifies and authorizes the TLS
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connection, and proxies back a standard TCP connection to the process.
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The sidecar service registration here is just telling Consul that a proxy should
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be running, Consul won't actually run a proxy process for you.
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We need to start the proxy process in another terminal:
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```shell-session
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$ consul connect proxy -sidecar-for socat
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==> Consul Connect proxy starting...
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Configuration mode: Agent API
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Sidecar for ID: socat
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Proxy ID: socat-sidecar-proxy
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...
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```
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## Connecting to the Service
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Next, let's connect to the service. We'll first do this by using the `consul connect proxy` command again directly. This time we use the command to configure
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and run a local proxy that can represent a service. This is a useful tool for
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development since it'll let you masquerade as any service (that you have
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permissions for) and establish connections to other services via Connect.
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The command below starts a proxy representing a service "web". We request
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an upstream dependency of "socat" (the service we previously registered)
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on port 9191. With this configuration, all TCP connections to 9191 will
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perform service discovery for a Connect-capable "socat" endpoint and establish
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a mutual TLS connection identifying as the service "web".
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```shell-session
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$ consul connect proxy -service web -upstream socat:9191
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==> Consul Connect proxy starting...
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Configuration mode: Flags
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Service: web
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Upstream: socat => :9191
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Public listener: Disabled
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...
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```
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With that running, we can verify it works by establishing a connection:
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```shell-session
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$ nc 127.0.0.1 9191
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hello
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hello
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```
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**The connection between proxies is now encrypted and authorized.**
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We're now communicating to the "socat" service via a TLS connection.
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The local connections to/from the proxy are unencrypted, but in production
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these will be loopback-only connections. Any traffic in and out of the
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machine is always encrypted.
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## Registering a Dependent Service
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We previously established a connection by directly running `consul connect proxy` in developer mode. Realistically, services need to establish connections
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to dependencies over Connect. Let's register a service "web" that registers
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"socat" as an upstream dependency in its sidecar registration:
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```shell-session
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$ cat <<EOF | sudo tee /etc/consul.d/web.json
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{
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"service": {
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"name": "web",
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"port": 8080,
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"connect": {
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"sidecar_service": {
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"proxy": {
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"upstreams": [{
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"destination_name": "socat",
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"local_bind_port": 9191
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}]
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}
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}
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}
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}
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}
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EOF
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```
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This registers a sidecar proxy for the service "web" that
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should listen on port 9191 to establish connections to "socat" as "web". The
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"web" service should then use that local port to talk to socat rather than
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directly attempting to connect.
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With that file in place, use `consul reload` or SIGHUP to reload Consul. If the
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proxy command from the previous section (with the inline upstream listener) is
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still running, stop it with `Ctrl-C`. Now we can start the web proxy using the
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configuration from the sidecar registration as we did for socat.
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```shell-session
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$ consul connect proxy -sidecar-for web
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==> Consul Connect proxy starting...
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Configuration mode: Agent API
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Sidecar for ID: web
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Proxy ID: web-sidecar-proxy
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==> Log data will now stream in as it occurs:
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2018/10/09 12:34:20 [INFO] 127.0.0.1:9191->service:default/socat starting on 127.0.0.1:9191
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2018/10/09 12:34:20 [INFO] Proxy loaded config and ready to serve
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2018/10/09 12:34:20 [INFO] TLS Identity: spiffe://df34ef6b-5971-ee61-0790-ca8622c3c287.consul/ns/default/dc/dc1/svc/web
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2018/10/09 12:34:20 [INFO] TLS Roots : [Consul CA 7]
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```
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Note in the first log line that the proxy discovered its configuration from the
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local agent and setup a local listener on port 9191 that will proxy to the socat
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service just as we configured in the sidecar registration.
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You can also see the identity URL from the certificate it loaded from the agent
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identifying it as the "web" service and the set of trusted root CAs it knows
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about.
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-> **Security note:** The Connect security model requires trusting
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loopback connections when proxies are in use. To further secure this,
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tools like network namespacing may be used.
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We can verify it works by establishing a new connection:
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```shell-session
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$ nc 127.0.0.1 9191
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hello
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hello
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```
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## Controlling Access with Intentions
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Intentions are used to define which services may communicate. Our connections
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above succeeded because in a development mode agent, the ACL system is "allow
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all" by default.
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Let's insert a rule to deny access from web to socat:
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```shell-session
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$ consul intention create -deny web socat
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Created: web => socat (deny)
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```
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With the proxy processes running that we setup previously, connection
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attempts now fail:
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```shell-session
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$ nc 127.0.0.1 9191
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$
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```
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Try deleting the intention and attempt the connection again.
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```shell-session
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$ consul intention delete web socat
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Intention deleted.
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$ nc 127.0.0.1 9191
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hello
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hello
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```
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Intentions allow services to be segmented via a centralized control plane
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(Consul). To learn more, read the reference documentation on
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[intentions](/docs/connect/intentions).
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Note that in the current release of Consul, changing intentions will not
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affect existing connections. Therefore, you must establish a new connection
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to see the effects of a changed intention. This will be addressed in the near
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term in a future version of Consul.
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## Discover More Connect
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This quick guide has given a taste of what Connect can do but there is much
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more. Take a look at [getting started with
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Connect](/docs/connect#getting-started-with-connect) for more guides
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on setting up Connect with Envoy proxy, with Docker and in Kubernetes.
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## Next Steps
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We've now configured a service on a single agent and used Connect for
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automatic connection authorization and encryption. This is a great feature
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highlight but let's explore the full value of Consul by [setting up our
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first cluster](/intro/getting-started/join)!
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