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!

}, “errors": [ { “subsystem": ‘pppoe’, “code": ”CONNECT_FAILED” } ] } -IP link: 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: ens2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr1 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x1 brd ff:ff:ff:ff:ff:ff altname enp1s0 3: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x2 brd ff:ff:ff:ff:ff:ff altname enp0s31f6 4: wls3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x3 brd ff:ff:ff:ff:ff:ff permaddr xx:xx:xx:xx:xx:x4 altname wlp2s0 5: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x2 brd ff:ff:ff:ff:ff:ff 6: vmbr1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x1 brd ff:ff:ff:ff:ff:ff 7: tap100i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master fwbr100i0 state UNKNOWN mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x5 brd ff:ff:ff:ff:ff:ff 8: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x6 brd ff:ff:ff:ff:ff:ff 9: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr1 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x7 brd ff:ff:ff:ff:ff:ff 10: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr100i0 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x6 brd ff:ff:ff:ff:ff:ff 13: veth107i0@if2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr0 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x8 brd ff:ff:ff:ff:ff:ff link-netnsid 0 14: veth107i1@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vmbr1 state UP mode DEFAULT group default qlen 1000 link/ether xx:xx:xx:xx:xx:x9 brd ff:ff:ff:ff:ff:ff link-netnsid 0

madduci/ftth_openwrt.md