I do a lot of my development work inside docker containers.  Recently I ran into an issue where, when connected to my company’s VPN network, the docker containers on my local machine running Fedora would lose the ability to connect to external resources.  Eventually I discovered the issue was that the default subnet created for the docker bridge interface on my Linux machine was overlapping with the subnet used by our corporate VPN.  So everything worked fine, as long as I wasn’t connected to the VPN.

My home network is a 10.x.x.x subnet, while my corporate VPN (and my default docker bridger interface) were bothing using 172.x.x.x.  So I opted to use 192.168.1.x for my docker bridge.  Making the change was fairly straightforward.  I needed to create the file /etc/docker/daemon.json.  The documentation describes a lot of options in this file, but all I needed was the following:

{
  "bip": "192.168.1.1/24"
}

Then I restarted docker:

sudo service docker restart

Problem solved!

Author: Eric Asberry
URL: https://a42.us/2017/06/14/SOLVED-Docker-Networking-On-Fedora-Linux-Fails-When-I-m-Connected-To-VPN/