Recently Deutsche Bahn started wifi for everyone travelling with a ICE. So far I had trips where it just worked great, on other trips I could not even connect – not on mobile phone nor on my laptop.
Today it was different
We have great signal strength, wifi on my phone works like a charm. Connecting to the wifi works nicely on the laptop as well. But I cannot connect to the login page for accepting t&c.
What happened – the analysis
I have a Thinkpad X1 Yoga laptop running Ubuntu 16.04. Among a gazillion of other packages docker is installed – mostly for dealing with lots of neo4j databases (of course ;-). The wifi (SSID: WIFIOnICE) itself is not authenticated but upon accessing the first webpage you get redirected to URL http://www.wifionice.de. Here I got a “cannot connect” error message in the browser. DNS lookups however worked fine – on couple of other WIFI issues DNS is a common culprit. Using
dig www.wifionice.de I’ve learned that this hostname resolves to IP address 172.18.10.10. Next to check are the routing tables:
stefan@x1 ➜ sudo route -n Kernel-IP-Routentabelle Ziel Router Genmask Flags Metric Ref Use Iface 0.0.0.0 172.16.0.1 0.0.0.0 UG 600 0 0 wlp4s0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 br-034d1e2af367 172.16.0.0 0.0.0.0 255.255.0.0 U 600 0 0 wlp4s0 172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0 172.18.0.0 0.0.0.0 255.255.0.0 U 0 0 0 br-034d1e2af367
Interesting, packages to 172.18.0.0/16 are routed to a weird interface called br-034d1e2af367 and are therefore not set via the wifi device. This finding justifies a loud WTF! This bridge interface is established by docker. Since I’m just a docker user without deep understanding of its internals I cannot really explain its exact purpose. But I don’t have to 😉
It’s good enough to just disable the bridge network interface while doing the wifi authentication:
ihtsudo ifconfig br-034d1e2af367 down open http://www.wifionice.de in your webbrowser and press the "go online" button sudo ifconfig br-034d1e2af367 up
After that operation I could use the internet on a ICE train without hassle.
a more elegant solution
Don’t have this one yet. I seems you can tweak the bridge’s IP number using
--bip <CIDR> upon docker startup. But I couldn’t find out the details for now. Happy to read your helpful comments here.
This post is mainly intended as a self-reminder for future train trips. If it’s helpful to others as well I’m more than happy. As a reference I’ve posted this in German language to a question on a forum of Deutsch Bahn as well.
9 replies on “WiFi at Deutsche Bahn + Ubuntu + Docker == trouble”
You saved me, thx man! I just couldn’t figure out why it was not working on my laptop while my smartphone had no problem at all!
Same for me! Thank you 🙂
Same here. Very useful! Thanks a lot!
Thanks – you made my trip much better
Saved my day)
great, works for me and you have made my day.
Dude, I didn’t know the dig command. I had all the information from the post in the Bahn forum but couldn’t make it work because the IP of wifionice.de changed. Dig showed it and… Connected!
In my case it wasn’t enough to just bring the weird interface down, I also needed to delete it.
Saved my work day! Thank you a lot! 🙂