G.INP / G.998.4 and routers/modems (ISP)

Hey everyone and anyone that works at the ISP level or deals with modem/routers, I've ran into what I think is going to be a huge issue for us, and I'm needing confirmation on my theory, or at least I hope proof that I'm wrong and out to lunch, about seems to be happening with our connections.

So we're a tier 3 ISP, last mile provider doing PPPoE over the local telco's lines. We have the following equipment deployed deployed within telco's service area for our clients to provide either dedicated circuits for voice, or data, or both;

• Cisco 1841, or 1921 with either adsl or VDSL2 WIC/HWIC's
• Cisco 1841, or 1921 connected to a Zyxel router/modem
• ZyXel 1432, or 3925

These circuits have been running without issue for anywhere from 4 years to a month, and in the last 4 months we've ran into the exact same issue twice - PPPoE PADI goes out, but nothing ever comes back, this is confirmed by telco, and our servers show no logs of the PPPoE connection being attempted. After too many hours troubleshooting and fighting with telco - who of course is insisting its our equipment, even though we've had 0 issues with it anywhere and tried swapping out router/modems to no success until coming to the exact same solution both times.

Starting back in Oct, telco started rolling out upgrades to their circuits with the G.INP / G.998.4 standard to, well to do exactly what that standard does, improve SNR on DSL circuits so as you can bump up the speeds and distances some because it lowers the amount of noise induced on the lines.

So now my theory - at least until I can get exact model numbers off the VDSL cards - from what I have found on the docs for Cisco ADSL and VDSL2 WIC's, they don't support G.INP / G.998.4, our ZyXel 1432 don't seem to either. But the ZyXel 3925 do explicitly state support for it.

The fix was putting in a new (new to us, just started deploying them in the last 6 months) ZyXel 3925 in bridge mode, the plugging our Cisco into it, and everything was good to go again.

So either I'm not googling the right terms for what I'm looking for, or people who know enough about this standard know what the issue is already and haven't posted about it online. So here I am, am I way off on this, if so, please point me in the right direction.

Thanks in advanced!

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