Lantiq VR9 fix for Ikanos DSLAM compatibility


I own a Zyxel VES-1608FA-35 DSLAM (why not) but it's quite old and not 100% compliant to standard.
In every place I know where Ikanos DSLAMS where deployed (Belgacom - Belgium and Bell Stinger - Canada) usually only Ikanos Modems or specially modified ones (special mode which can be enabled in Firmware) are reported to work at all. But all of this modems are getting quite old now (and I would expect the DSLAM to outlive the el cheapo CPEs...)

TLDR; Now to the question:
How much of the Handshake/Training protocol is handled on the CPU (kernel module and user space daemon) vs the firmware blob?

Best case just some pre-standard feature flags need to be send/accepted and the lantiq can sync - Worst case a SDR firmware patch would be needed which would be a dead end of course (unless there is Ghidra support for the architecture and the blobs aren't signed, but still meh)
The more magic is happening on the CPU (and the code to which we have sources), the higher are my chances to debug/understand the issue.

Did you get anywhere? I own a VES-1608FA-35 but I cannot even get a Fritzbox 7930 with an Ikanos Chipsatz to work and the official am Firmware to work, let alone openwrt.

Did you find any documentation on the wiring? Could you elaborate on your setup? I only have 4 wires in the walls and Ethernet barely connects. Using a DSLAM and multiple routers in house might allow better traffic control for the kids...

Yes I asked a million places. I eventually learned that Chaosvermittlung has deployed these DSLAMs along their field phone service on some CCC conference. They were apparently able to source a newer Firmware which conforms better with the VDSL2 standard and supports most modems.

It runs very stable for me with mostly default settings and FritzBoxes (e.g. used 7412) as well as an SFP modem from

The updated Firmware is V3.60(AYZ.5)b11, I guess you are running V3.60(ARN) ?

I will send you a link via DM. Although it might be possible this can be uploaded to as well since the support basically ended 10 years ago but I am not sure.