Connecting Containers Across Hosts with an Overlay Network and Cleanup

> Notice the returned **NETWORK ID** -- you will see it again when you connect to it from `host2`. 3. On `host1`, start an interactive (`-it`) container (`alpine1`) that connects to `test-net`: ```console $ docker run -it --name alpine1 --network test-net alpine / # ``` 4. On `host2`, list the available networks -- notice that `test-net` does not yet exist: ```console $ docker network ls NETWORK ID NAME DRIVER SCOPE ec299350b504 bridge bridge local 66e77d0d0e9a docker_gwbridge bridge local 9f6ae26ccb82 host host local omvdxqrda80z ingress overlay swarm b65c952a4b2b none null local ``` 5. On `host2`, start a detached (`-d`) and interactive (`-it`) container (`alpine2`) that connects to `test-net`: ```console $ docker run -dit --name alpine2 --network test-net alpine fb635f5ece59563e7b8b99556f816d24e6949a5f6a5b1fbd92ca244db17a4342 ``` > [!NOTE] > > Automatic DNS container discovery only works with unique container names. 6. On `host2`, verify that `test-net` was created (and has the same NETWORK ID as `test-net` on `host1`): ```console $ docker network ls NETWORK ID NAME DRIVER SCOPE ... uqsof8phj3ak test-net overlay swarm ``` 7. On `host1`, ping `alpine2` within the interactive terminal of `alpine1`: ```console / # ping -c 2 alpine2 PING alpine2 (10.0.0.5): 56 data bytes 64 bytes from 10.0.0.5: seq=0 ttl=64 time=0.600 ms 64 bytes from 10.0.0.5: seq=1 ttl=64 time=0.555 ms --- alpine2 ping statistics --- 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max = 0.555/0.577/0.600 ms ``` The two containers communicate with the overlay network connecting the two hosts. If you run another alpine container on `host2` that is _not detached_, you can ping `alpine1` from `host2` (and here we add the [remove option](/reference/cli/docker/container/run/#rm) for automatic container cleanup): ```sh $ docker run -it --rm --name alpine3 --network test-net alpine / # ping -c 2 alpine1 / # exit ``` 8. On `host1`, close the `alpine1` session (which also stops the container): ```console / # exit ``` 9. Clean up your containers and networks: You must stop and remove the containers on each host independently because Docker daemons operate independently and these are standalone containers. You only have to remove the network on `host1` because when you stop `alpine2` on `host2`, `test-net` disappears. a. On `host2`, stop `alpine2`, check that `test-net` was removed, then remove `alpine2`: ```console $ docker container stop alpine2 $ docker network ls $ docker container rm alpine2 ``` a. On `host1`, remove `alpine1` and `test-net`: ```console $ docker container rm alpine1 $ docker network rm test-net ``` ## Other networking tutorials - [Host networking tutorial](/manuals/engine/network/tutorials/host.md) - [Standalone networking tutorial](/manuals/engine/network/tutorials/standalone.md) - [Macvlan networking tutorial](/manuals/engine/network/tutorials/macvlan.md)

This section details connecting containers on different hosts (`host1` and `host2`) via the overlay network `test-net`. It shows how to start a detached container (`alpine2`) on `host2` connected to `test-net`, verifies the network's creation and shared NETWORK ID on both hosts, and demonstrates inter-container communication using ping from `alpine1` (on `host1`) to `alpine2` (on `host2`). It also shows running a temporary alpine container on `host2` that is not detached to ping alpine1. Finally, it outlines the cleanup process, including stopping and removing containers on both hosts independently and removing the network.