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Swarm and container networks
docker, swarm, clustering, networking
Swarm and container networks

Docker Swarm is fully compatible with Docker's networking features. This includes the multi-host networking feature which allows creation of custom container networks that span multiple Docker hosts.

Before using Swarm with a custom network, read through the conceptual information in Docker container networking. You should also have walked through the Get started with multi-host networking example.

Create a custom network in a Swarm cluster

Multi-host networks require a key-value store. The key-value store holds information about the network state which includes discovery, networks, endpoints, IP addresses, and more. Through the Docker's libkv project, Docker supports Consul, Etcd, and ZooKeeper key-value store backends. For details about the supported backends, refer to the libkv project.

To create a custom network, you must choose a key-value store backend and implement it on your network. Then, you configure the Docker Engine daemon to use this store. Two required parameters, --cluster-store and --cluster-advertise, refer to your key-value store server.

Once you've configured and restarted the daemon on each Swarm node, you are ready to create a network.

List networks

This example assumes there are two nodes node-0 and node-1 in the cluster. From a Swarm node, list the networks:

$ docker network ls
NETWORK ID          NAME                   DRIVER
3dd50db9706d        node-0/host            host
09138343e80e        node-0/bridge          bridge
8834dbd552e5        node-0/none            null
45782acfe427        node-1/host            host
8926accb25fd        node-1/bridge          bridge
6382abccd23d        node-1/none            null

As you can see, each network name is prefixed by the node name.

Create a network

By default, Swarm is using the overlay network driver, a global-scope network driver. A global-scope network driver creates a network across an entire Swarm cluster. When you create an overlay network under Swarm, you can omit the -d option:

$ docker network create swarm_network
42131321acab3233ba342443Ba4312
$ docker network ls
NETWORK ID          NAME                   DRIVER
3dd50db9706d        node-0/host            host
09138343e80e        node-0/bridge          bridge
8834dbd552e5        node-0/none            null
42131321acab        node-0/swarm_network   overlay
45782acfe427        node-1/host            host
8926accb25fd        node-1/bridge          bridge
6382abccd23d        node-1/none            null
42131321acab        node-1/swarm_network   overlay

As you can see here, both the node-0/swarm_network and the node-1/swarm_network have the same ID. This is because when you create a network on the cluster, it is accessible from all the nodes.

To create a local scope network (for example with the bridge network driver) you should use <node>/<name> otherwise your network is created on a random node.

$ docker network create node-0/bridge2 -b bridge
921817fefea521673217123abab223
$ docker network create node-1/bridge2 -b bridge
5262bbfe5616fef6627771289aacc2
$ docker network ls
NETWORK ID          NAME                   DRIVER
3dd50db9706d        node-0/host            host
09138343e80e        node-0/bridge          bridge
8834dbd552e5        node-0/none            null
42131321acab        node-0/swarm_network   overlay
921817fefea5        node-0/bridge2         bridge
45782acfe427        node-1/host            host
8926accb25fd        node-1/bridge          bridge
6382abccd23d        node-1/none            null
42131321acab        node-1/swarm_network   overlay
5262bbfe5616        node-1/bridge2         bridge

Remove a network

To remove a network you can use its ID or its name. If two different networks have the same name, include the <node> value:

$ docker network rm swarm_network
42131321acab3233ba342443Ba4312
$ docker network rm node-0/bridge2
921817fefea521673217123abab223
$ docker network ls
NETWORK ID          NAME                   DRIVER
3dd50db9706d        node-0/host            host
09138343e80e        node-0/bridge          bridge
8834dbd552e5        node-0/none            null
45782acfe427        node-1/host            host
8926accb25fd        node-1/bridge          bridge
6382abccd23d        node-1/none            null
5262bbfe5616        node-1/bridge2         bridge

The swarm_network was removed from every node. The bridge2 was removed only from node-0.

Docker Swarm documentation index