Billion UK Forum

I woke up this morning with no net connection. My month or two old 7800n had a syslog looking like this:

Aug 22 07:10:30 user kernel: Line 0: ADSL link down
Aug 22 07:10:32 user kernel: Line 0: xDSL G.994 training
Aug 22 07:10:37 user kernel: Line 0: ADSL G.992 started
Aug 22 07:10:40 user kernel: Line 0: ADSL G.992 channel analysis
Aug 22 07:10:44 user kernel: Line 0: ADSL link down
Aug 22 07:10:45 user kernel: Line 0: xDSL G.994 training
Aug 22 07:10:51 user kernel: Line 0: ADSL G.992 started
Aug 22 07:10:54 user kernel: Line 0: ADSL G.992 channel analysis
Aug 22 07:10:58 user kernel: Line 0: ADSL link down

... and added another four lines every few seconds as it kept retrying to connect. Everything else on the router I used was working okay. I was connected to it over wifi and the control interface worked fine. I switched microfilters to no avail, and after half an hour on the phone (which was working okay) the ISP could find no easily detectable fault on the line and prompted me to try an older router. I plugged that in instead and after a bit of a faff (as it has no wifi) I worked out that it had synced, logged in, and internet access was working fine. So, apparently the line is okay.

I haven't had any time before coming in to work to try factory resets etc. on the 7800N, but I'm just wondering if anyone has seen one fail like this before?

I have been fiddling with the SNR settings in the last couple of weeks but not tweaked anything for a few days now and it was working okay last night; so I'm guessing it's some kind of hardware fault, but limited only to the modem circuits. Is that a reasonable diagnosis, or does anyone have any other ideas?

Try the reset back to factory default normally this will resolve the issue.

Okay - It's fixed. Thanks for that.

For the record, this is what I've diagnosed had caused it. A complete factory reset got things working again (once I'd remembered my account password etc.) but a subsequent restore of the config from when it was broken did reliably break it again. I had quite a lot of settings I didn't want to have to go through entering again so I went through the diffs of the bad config with the factory reset config taking suspect settings out one at a time.

It turned out that it was the SNR tweak. If I set that back to -1 (default) it connected fine and all the other settings were restored as well. So I had a closer look at the line stats and what I think happened to cause the error is that for some reason my line improved dramatically last night! Previously I'd had the SNR up in the 12-15dB range so I'd applied a hefty SNR tweak to drop the reported value down, but when I reconnected with the factory settings just now the base SNR had dropped to ~6dB. This was lower than the amount by which the modem was configured to tweak it, so the modified value would have been negative! (Roughly -3dB, I think.) I'm not sure if that was causing some kind of underflow floating point exception, or similar, in the 7800N preventing connection; or maybe the kit at the exchange was too gripped by a giggling fit to respond.