Sep 15, 2022

Deutsche Bahn Docker

If you have Docker installed on Linux, you can’t log into the Wifi on a train with Deutsche Bahn. After searching for a while, I found out that the captive portal, which is needed to accept the Terms of Service is accessible on 172.18.0.1 - unfortunatley docker already did set up a bridge br-296018cca038 with the same IP address.

One can remove the bridge with sudo ip link d br-296018cca038 until docker restarts or remove unused bridges with docker network prune -f.

To solve the root of the problem one has to change the address pool docker uses in the /etc/docker/daemon.json like this:

{
  "bip": "172.26.0.1/16",
  "default-address-pools": [
    { "base": "172.27.0.0/16", "size": 20 }
  ]
}

Of course, this can lead to problems in other corporate networks where this address pool is already used, but for WIFIonICE this is a solution for now.