Modify Docker Default Bridge Address

A colleague from the school studio reported that after using Docker, its default 172 bridge address conflicted with a subnet in one of the dorm buildings, preventing students in that area from accessing Docker applications properly. After going through the official documentation, I found a way to modify the default bridge address.

First, stop the Docker service:

$ sudo service docker stop

Next, delete Docker’s default bridge docker0:

$ sudo ip link set dev docker0 down
$ sudo brctl delbr docker0
$ sudo iptables -t nat -F POSTROUTING

Then, create a new bridge. Note that you can replace bridge0 with any other name, and 192.168.5.1/24 can also be replaced with another subnet of your choice:

$ sudo brctl addbr bridge0
$ sudo ip addr add 192.168.5.1/24 dev bridge0
$ sudo ip link set dev bridge0 up

Check if the new bridge is functioning correctly:

$ ip addr show bridge0
4: bridge0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state UP group default
    link/ether 66:38:d0:0d:76:18 brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.1/24 scope global bridge0
       valid_lft forever preferred_lft forever

Now, write the new bridge configuration into Docker’s default configuration file and start Docker:

$ echo 'DOCKER_OPTS="-b=bridge0"' >> /etc/default/docker
$ sudo service docker start

Reference: https://docs.docker.com/v1.8/articles/networking/#bridge-building