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If you still can't connect using German railway Deutsche Bahn's WiFi on ICE network from a Ubuntu / Linux system, the reason might be that you're a dev an using Docker with the standard configuration which has an address conflict with WIFIonICE at 172.18.0.0/16. Thanks to German UbuntuUsers forum: Probleme mit dem WIFIonICE for pointing out!
A quick workaround, unless you actually have to use Docker while working on a train (of course you do), you can stop Docker, optionally also prune its networks and try to explicitly clear 172.18.0.0/16 using the br- address that you can find out using the ifconfig command. Thus:
ip a to check if you are actually connected to any network.
ip a | grep docker to check if Docker is a potential problem and find out its name to use for shutting it down.
$ ip a | grep docker
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
$ sudo ifconfig docker0 down
$ docker network prune
WARNING! This will remove all custom networks not used by at least one container.
Are you sure you want to continue? [y/N] y
Deleted Networks:
...
Last but not least, if needed, use ifconfig to find out the conflicting broadcast address.
$ ifconfig -a | grep br
br-2abd62f2e2aa: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 172.18.0.1 netmask 255.255.0.0 broadcast 172.18.255.255
br-7eeffe1d5437: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.0.1 netmask 255.255.0.0 broadcast 172.20.255.255
br-a5a3fb8bd4be: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 172.19.0.1 netmask 255.255.0.0 broadcast 172.19.255.255
inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255
inet 172.18.105.167 netmask 255.255.0.0 broadcast 172.18.255.255
$ sudo ip -4 addr del 172.18.0.0/16 dev br-2abd62f2e2aa
RTNETLINK answers: Cannot assign requested address
See the forum post (or any other helpful documentation) on how to permanently reconfigure Docker to use an alternative network address, for example this post on ServerFault: Configuring Docker to not use the 172.17.0.0 range:
Edit or create /etc/docker/daemon.json config file for docker daemon
using the alternate address pool suggested in the comments to avoid another address collision conflict
If you still can't connect using German railway Deutsche Bahn's WiFi on ICE network from a Ubuntu / Linux system, the reason might be that you're a dev an using Docker with the standard configuration which has an address conflict with WIFIonICE at
172.18.0.0/16. Thanks to German UbuntuUsers forum: Probleme mit dem WIFIonICE for pointing out!A quick workaround, unless you actually have to use Docker while working on a train (of course you do), you can stop Docker, optionally also prune its networks and try to explicitly clear
172.18.0.0/16using thebr-address that you can find out using theifconfigcommand. Thus:ip ato check if you are actually connected to any network.ip a | grep dockerto check if Docker is a potential problem and find out its name to use for shutting it down.Last but not least, if needed, use
ifconfigto find out the conflicting broadcast address.Then reload the captive page or iceportal.de/
See the forum post (or any other helpful documentation) on how to permanently reconfigure Docker to use an alternative network address, for example this post on ServerFault: Configuring Docker to not use the 172.17.0.0 range: