In correlation with the end of life (EOL) for MKE 3.6.x, maintenance of this documentation set was discontinued as of 2024-OCT-13. Click here for the latest MKE 3.x version documentation.

docker_gwbridge¶

The docker_gwbridge is a virtual network interface that connects overlay networks (including ingress) to individual MCR container networks. Initializing a Docker swarm or joining a Docker host to a swarm automatically creates docker_gwbridge in the kernel of the Docker host. The default docker_gwbridge subnet (172.18.0.0/16) is the second available subnet in default-address-pools.

To change the docker_gwbridge subnet, open daemon.json and modify the second pool in default-address-pools:

{
    "default-address-pools": [
       {"base":"172.17.0.0/16","size":16},
       {"base":"172.18.0.0/16","size":16}, <-- Modify this value
       {"base":"172.19.0.0/16","size":16},
       {"base":"172.20.0.0/16","size":16},
       {"base":"172.21.0.0/16","size":16},
       {"base":"172.22.0.0/16","size":16},
       {"base":"172.23.0.0/16","size":16},
       {"base":"172.24.0.0/16","size":16},
       {"base":"172.25.0.0/16","size":16},
       {"base":"172.26.0.0/16","size":16},
       {"base":"172.27.0.0/16","size":16},
       {"base":"172.28.0.0/16","size":16},
       {"base":"172.29.0.0/16","size":16},
       {"base":"172.30.0.0/16","size":16},
       {"base":"192.168.0.0/16","size":20}
   ]
}

Caution

Modifying the first pool to customize the docker0 subnet can affect the default docker_gwbridge subnet. Refer to docker0 for more information.
You can only customize the docker_gwbridge settings before you join the host to the swarm or after temporarily removing it.