I am pretty sure the majority of us are affected by IPv6 being turned on in our modems.
As of this writing my SB6120 has been up 8 days 2 hours. I had the same problems everyone else has described (from late June-Aug 7), including dealing with phone calls and e-mails with Comcast support, two tech visits, purchasing a new SB6121, purchasing new cable and connectors, etc. My upstream is typically 50-52db. The techs told me that is as good as I am going to get it for my area--Staunton, VA.
Where the cable enters the house I have 46db-48db, add one splitter -3.5db and I am at 50-52, so I guess that proves them out.
On August 7 around noon, I had my last reboot because of a T4 timeout error. Previously these reboots would occur from 1-5 times a day. My upload level seems to stay at 52db consistently. My download speeds are about 35Mbps, upload near 4.5Mbps.
I have looked over the modem's settings and there are two things that look different to me. The first is the Ranging Service ID. I believe it is a different number than before, but a search of the internet doesn't tell me anything about what this ID represents. The second thing that has changed is found in the Config tab I don't see a reference to IPv6 any more.
Frequency Plan: North American Standard/HRC/IRC Custom Frequency Ordering:
Default Upstream Channel ID: 4
Favorite Frequency (Hz) 627000000
DOCSIS MIMO IPv4 Only
Modem's IP Mode IPv4 Only
There is a post earlier in this thread that spoke to turning off IPv6 on your router to solve the problem, I think the person posting was using an Apple airport. I didn't try that I was figuring there was a hardware problem upstream in the Comcast infrastructure--we've had some wicked lightning storms this summer.
But now my modem has been stable for seven days. The other thing that I have now noticed is that the errored codewords (correctable and uncorrectable) don't change much if at all. Before when I kept dropping connections to the internet I would say that the uncorrectable numbers were at least 10% of the unerrored codewords and the numbers climbed together.
Channel ID 210 209 211 212
Total Unerrored Codewords 30305725694 26010758518 26010758523 26010758523
Total Correctable Codewords 21 11 8 9
Total Uncorrectable Codewords 1576 1402 1402 1402
Bottom line, if the line is stable, even at 52db upstream power level the errors seem to be non-existent and connectivity seems solid. The SB6120 spec states a max of 58db, the Motorola site says it would prefer 42-50db, but 52db is in spec and for the last 8 days 2 hours of experience it seems to be holding just find at that level.
I do have a new error I never have seen before, plus it seems to replace itself rather than adding to the log.
Aug 13 2012 14:48:13 4-Error D103.0
DHCP RENEW WARNING - Field invalid in response v4 option...
I got the first of these errors on Aug 10, 3 days after being stable, then again on the 13th. But the error from the 10th was then gone, only the error from the 13 showed at the top of the log--as if it had been overwritten. I should also mentioned that I typically got errors all day long about T3, T4, etc. In the last 8 plus days I have only received one message in the log about DHCP renew and it appears to write over itself. COOL!
If your Comcast group still shows IPv6 in your modems config I would ask them to try setting to IPv4 only. It can't hurt.
Good Luck to Us All!
