Changing the IP range for docker0

Lately, I’ve been tinkering a lot with docker. Mostly, I’ve been doing it for work at The Linux Foundation. But I do have a desire to have docker instances on my local box for distros which I do not run.

While doing some testing for work on my personal laptop, I noticed that the network which docker uses for it’s bridge, aptly named docker0, was in the same network as one of our VPNs.

# ip a s docker0
7: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 ...
 link/ether fe:54:00:18:1a:fd brd ff:ff:ff:ff:ff:ff
 inet brd scope global docker0

# ip a s tun0
    inet brd scope global tun0
       valid_lft forever preferred_lft forever

As you can tell, the docker0 network bridge covers all of the tun0 network. Any time I would attempt to ssh into one of the systems inside the VPN, it would time out. I was left wondering why for a few moments.

Luckily, it’s very easy to fix this problem. All that is needed is a defined bridge for docker0 and to restart the docker service. Here’s what to do:

First, stop docker:

# service docker stop
Redirecting to /bin/systemctl stop  docker.service

Next, create the network bridge file. You can choose any IP range you like. On Fedora 19, it looks like this:

# cat /etc/sysconfig/network-scripts/ifcfg-docker0 

Restart your network services.  NOTE: service network restart may be needed.

# service NetworkManager restart
Redirecting to /bin/systemctl restart  NetworkManager.service

The docker0 bridge should now be in a range outside the VPN.

# ip a s docker0
7: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 ...
    link/ether fe:54:00:18:1a:fd brd ff:ff:ff:ff:ff:ff
    inet brd scope global docker0

Starting new containers with docker should get IP addesses in the above range:

# service docker start
Redirecting to /bin/systemctl start  docker.service

# docker run -i -t herlo/fedora:20 /bin/bash
bash-4.2# ip a s eth0
141: eth0: <BROADCAST,UP,LOWER_UP> mtu 1412 ...
    link/ether fa:5f:e3:8d:61:f2 brd ff:ff:ff:ff:ff:ff
    inet scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::f85f:e3ff:fe8d:61f2/64 scope link 
       valid_lft forever preferred_lft forever




This entry was posted in docker, Fedora, Networking and tagged , , , . Bookmark the permalink.

3 Responses to Changing the IP range for docker0

  1. Andrea says:

    Thanks – had the same problem, but how did you solve that in Ubuntu? THANKS.

  2. herlo says:

    Unfortunately, I am not as familiar with how to set up a bridge on Ubuntu. I would guess there are plenty of tutorials on how to setup a bridge on Ubuntu.

    Good luck,


  3. Steve Kamerman says:

    Here’s the script that I wrote for changing the docker0 IP on debian / ubuntu:

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