docker network connect

Description

Connects a container to a network. You can connect a container by name or by ID. Once connected, the container can communicate with other containers in the same network.

Options

Examples

Connect a running container to a network

$ docker network connect multi-host-network container1

Connect a container to a network when it starts

You can also use the docker run --network=<network-name> option to start a container and immediately connect it to a network.

$ docker run -itd --network=multi-host-network busybox

Specify the IP address a container will use on a given network (--ip)

You can specify the IP address you want to be assigned to the container's interface.

$ docker network connect --ip 10.10.36.122 multi-host-network container2

Use the legacy --link option (--link)

You can use --link option to link another container with a preferred alias.

$ docker network connect --link container1:c1 multi-host-network container2

Create a network alias for a container (--alias)

--alias option can be used to resolve the container by another name in the network being connected to.

$ docker network connect --alias db --alias mysql multi-host-network container2

Set sysctls for a container's interface (--driver-opt)

sysctl settings that start with net.ipv4. and net.ipv6. can be set per-interface using --driver-opt label com.docker.network.endpoint.sysctls. The name of the interface must be replaced by IFNAME.

To set more than one sysctl for an interface, quote the whole value of the driver-opt field, remembering to escape the quotes for the shell if necessary. For example, if the interface to my-net is given name eth3, the following example sets net.ipv4.conf.eth3.log_martians=1 and net.ipv4.conf.eth3.forwarding=0.

$ docker network connect --driver-opt=\"com.docker.network.endpoint.sysctls=net.ipv4.conf.IFNAME.log_martians=1,net.ipv4.conf.IFNAME.forwarding=0\" multi-host-network container2

Note

Network drivers may restrict the sysctl settings that can be modified and, to protect the operation of the network, new restrictions may be added in the future.

Network implications of stopping, pausing, or restarting containers

You can pause, restart, and stop containers that are connected to a network. A container connects to its configured networks when it runs.

If specified, the container's IP address(es) is reapplied when a stopped container is restarted. If the IP address is no longer available, the container fails to start. One way to guarantee that the IP address is available is to specify an --ip-range when creating the network, and choose the static IP address(es) from outside that range. This ensures that the IP address is not given to another container while this container is not on the network.

$ docker network create --subnet 172.20.0.0/16 --ip-range 172.20.240.0/20 multi-host-network

$ docker network connect --ip 172.20.128.2 multi-host-network container2

To verify the container is connected, use the docker network inspect command. Use docker network disconnect to remove a container from the network.

Once connected in network, containers can communicate using only another container's IP address or name. For overlay networks or custom plugins that support multi-host connectivity, containers connected to the same multi-host network but launched from different Engines can also communicate in this way.

You can connect a container to one or more networks. The networks need not be the same type. For example, you can connect a single container bridge and overlay networks.