Deutsche Telekom FTTH Access with OpenWRT

ftth_openwrt.md

Configuring Deutsche Telekom FTTH Access with OpenWRT

After looking for alternatves to the suggested Router from Telekom (AVM FritzBox and HUawei Speedport), I've discovered the possibility of configuring my existing OpenWRT Router to act as gateway to the Telekom FTTH (Fiber To The Home) Magenta Zuhause package.

TL;DR

The WAN interface must be configured as follows (see your Telekom letter):

• Protocol: PPPoE
• PAP/CHAP username:
  • Zugangsnummern with 12+ Digits/Chars: [email protected]
  • Zugangsnummern with less than 12 Digits/Chars: AnschlusskennungZugangsnummer#[email protected]
• PAP/CHAP password: Zugangskenntwort
• VLAN: 7
• MTU: leave empty (delete the default value 1500)

Requirements

Access Data

Old Contracts (Before 2024)

It's important to know the following information, before attempting any connection:

• Anschlusskennung
• Zugangsnummer
• Mitbenutzernummer
• Zugangskenntwort

All the above information are typically sent by Telekom at home, when activating the Internet Access.

Newer Contracts (From 2024)

The "Easy Login" option is automatically activated for new contracts. If it is activated, you can use any username/password. Otherwise it can activated in the "Kundencenter".

Otherwise it's important to know the following information, before attempting any connection:

Anschlusskennung
Zugangsnummer
Mitbenutzernummer
Zugangskenntwort

All the above information can be found oin the "Kundencenter" at "Verträge" -> "Erweiterte Optionen" -> "Internetzugang".

Hardware

You need a OpenWRT-capable router (e.g. TP-Link Archer C7 works really well), see here for an exhaustive list of supported devices.

Make sure your Telekom Fiber Modem is working properly.

Configuration

Enable VLAN

The Telekom PPPoE access requires the VLAN-ID to be set to 7. In order to do so, you have to configure the Router Ethernet interface that refers to WAN. The configuration panel can be found under the Menu entry Network->Switch (on OpenWRT 22.03 is Network -> Devices -> Add Device Config)

In this panel, you can see a table showing the VLAN(s) configured for your Router (typically 2) and they have some comboboxes with status tagged/untagged/off. One of the VLANs configured should be configured with the following information:

Port Status	CPU (eth0)	LAN1	LAN2	LAN3	LAN4	WAN
1	tagged	untagged	untagged	untagged	untagged	off
7	tagged	off	off	off	off	tagged

In case of Routers with multiple Ethernet interfaces (e.g. TP-Link Archer C7), the panel should look like this:

Port Status	CPU (eth0)	CPU (eth0)	LAN1	LAN2	LAN3	LAN4	WAN
1	tagged	tagged	untagged	untagged	untagged	untagged	off
7	tagged	tagged	off	off	off	off	tagged

Setup WAN Interface

In the Menu entry Network->Interfaces, select the WAN interface and set the following information in the General Setup tab:

• Protocol: PPPoE
• PAP/CHAP username: [email protected]
• PAP/CHAP password: Zugangskenntwort

In the tab Physical Settings, select the interface Switch VLAN eth0.7 (the one corresponding to the VLAN-ID 7).

Beware: in case your "Zugangsnummer" has less than 12 digits, the PAP/CHAP username is in the form AnschlusskennungZugangsnummer#[email protected] (see https://telekomhilft.telekom.de/t5/Telefonie-Internet/PPPOE-Einwahl-ueber-einen-Router-herstellen/ta-p/3654990 for further details)

Performance Tuning

MTU should not be set to an MTU of 1500 in any WAN, PPPOE-WAN or VLAN 7 interface - it automatically negotiates an MTU of 1492 when dialing in. Make sure that in none of the above mentioned interfaces in the field MTU is a real value in it.

Check the /etc/config/network file or execute uci show network over ssh for any configured mtu:

config interface 'wan'
option proto 'pppoe'
option device 'eth0.7'
option username '[email protected]'
option password 'xxx'
option ipv6 'auto'

This change improves the performance with Applications/Services such as MS Teams, Speedtests and many other ones.

Happy surfing!

@madduci Does telekom provide an ONT even if I select that I don't want to rent a modem and I have my own? I see an option to buy something called fiber modem 2 for 50 euros instead of renting as well. Is that the ONT? If so it seems wrong for them to sell an ONT which will probably just work for their network to people who don't want to pay rent for the modem but I couldn't find definitive answers anywhere. I just need a way to be able to use my own openwrt modem without paying rent with fiber

@osmanozturk I bought Zyxel Gigabit GPON SFP-Type SFU (telecom provide it for biz customers) works for me without paying them for modem, one downside that I observe after ~1y of usage is that on avg once in 5-6 months I may need to reconnect it (probably because of overheat, that could be specific to my setup or device), so in general you can use any fiber modem, they dont really care, but you need to be able to make vlan.7 on top with your creds, hope that helps

@v01t Thanks for the help but it didn't clear up my confusion. Sorry for my lack of knowledge when it comes to fiber. I didn't use anything other than dsl up until now. So do I have to buy the ONT myself or a modem? What I am understanding is only having a router won't cut it. Is that right?

@osmanozturk ONT - Optical Network Terminal, in simple terms device where you insert your fiber cable and that's where "fiber" terminated but that's not enough in some setups as you still need to "authorize" on top, telecom for private customers selling "modems" that do both, but depending on your need you dont require to buy/rent their "modems" and use your own device(s).

In my setup I were trying to reduce number of devices in chain, I have first switch in my network that has SFP in it, so I use above gpon modem as ONT to terminate fiber, and then inside of router I do vlan.7 over it, and then over it PAP or whatever its called to do auth (login /password)

Hope this brings more clues than confusion :)