Your own router with Deutsche Telekom
Using your own router behind "Glasfaser Modem 2" is really simple. It's just that Deutsche Telekom aren't very helpful.
There's a nice guide here for OpenWRT routers. The basic steps apply to any router:
- Use PPPoE for the WAN interface
- Use your Internet-Zugangsnummer as the username
- Use your Persönliches Kennwort as the password
- VLAN-tag your internet traffic with 7 (and IPTV with 8)
Every router has these settings in different places, most of which make little sense to me. Below, I'll show what you need to do on three different routers:
DD-WRT
First, select PPPoE in WAN Connection Type. Then fill out the username and password. Next, check Advanced Settings three lines below, and then select T-Online VLAN 7 Support.
At this point, you probably want to restart your router, and then it should all work!
Asus AC3200
In WAN Settings, pick PPPoE and fill out the username and password. Go to LAN and then IPTV. There, you can enable VLAN tagging — just fill in 7 for internet, possibly restart, and it should start working.
Netgear R7000
Similar to the Asus for WAN settings, but I never configured VLAN tagging here since I got the Asus working and then installed DD-WRT on this router. However, their guide here describes how to tag properly.
Why make it so hard?
Deutsche Telekom is valued at around 85 billion USD. It's fascinating that they can't just put something like this in their guides:
For the smoothest experience with setting up your new fibre connection, we recommend using one of these five routers, where you will get full Telekom support.
If you prefer using a router Telekom doesn't support, you will need to tag your traffic with 7 for normal internet traffic and 8 for IPTV. Your credentials can be found on "this page" in your account. Be aware that Telekom will not be able to offer support.
Then, if you don't want to throw away perfectly good hardware and you have the knowledge, you can do so without spending a lot of time searching the internet. If it feels overwhelming, or if you need a new router anyway, you can just go with one of theirs.