Ubuntu ICE wifi

A clean Ubuntu 20.04 should work well with WifiOnIce serivce, but there may occure problems when using third-party software which is using the same local ip address range as the Deutsche Bahn network.

Docker

Docker network bridge is blocking the ip range WifiOnIce is using for their services.

List all your devices

ip addr

Output should be somewhat similar to this:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc ...
    link/ether 00:2b:67:a4:21:35 brd ff:ff:ff:ff:ff:ff
3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 08:d2:3e:ed:af:17 brd ff:ff:ff:ff:ff:ff
    inet 192.168.43.189/24 brd 192.168.43.255 scope global dynamic noprefixroute wlp3s0
       valid_lft 3445sec preferred_lft 3445sec
    inet6 fe80::9599:5183:d50a:fab/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
4: br-c5332f9b3162: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 02:42:1a:91:59:2a brd ff:ff:ff:ff:ff:ff
    inet 172.18.0.1/16 brd 172.18.255.255 scope global br-c5332f9b3162
       valid_lft forever preferred_lft forever
5: br-ce81f2e3a9fa: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 02:42:43:e0:9f:b8 brd ff:ff:ff:ff:ff:ff
    inet 172.20.0.1/16 brd 172.20.255.255 scope global br-ce81f2e3a9fa
       valid_lft forever preferred_lft forever
6: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether 02:42:2c:fc:fd:6c brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever

First, figure out which bridge might block the traffic to the DB WiFi services. For me it was the network bridge with the following broadcast address:

brd 172.18.255.255

sudo ip link delete br-c5332f9b3162

Now it should work, otherwise you can try to delete all suspicous links one by one to find the right one.