hi @ all ...
in our little plant a cisco cmts ubr7246 with NPE-G1 12.3(23) and an old uBR-MC28u (EuroDOCSIS 2) Linecard is working fine until now we connected the AVM Fritzbox 6660 to it.
The Router´s LED is blinking and in GUI Downstream Channel found ist displayed but nothing more.
In CMTS the modem isn´t there.
So i think the Box doesn´t come in Upstream Ranging but doesn´t know why.
Maybe some of you have the same problem ? Maybe it isn´t downward compatible.
All other Boxes are perfectly online. And tested other 6660 (the same problem).
thanks
best regards
Marek
By specification DOCSIS 3.1 cable modems are not compatible with (Euro)DOCSIS 1.x/2.0.
DOCSIS 3.1 cable modems looking for a MDD (MAC Domain Descriptor) in the SC-QAM Channels. This MDD messages was introduced with (Euro)DOCSIS 3.0. Is this MDD message missing, the cable modem will leaving the SC-QAM and will scan for another SC-QAM channel.
Or in other words: DOCSIS 3.1 cable modems are ONLY backward compatible with (Euro)DOCSIS 3.0.
On Broadcom-Silicon based cable modems I saw that's possible to activate a legacy mode but this is not easy to configure. For Maxlinear-Silicon, like in the 6660 I don't know... so likely the D3.1 CM is only compatible with 3.1 with 3.0.
Sorry for having no better news.