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GotNoRice
Internet Cynic

join:2001-12-04
Pleasant Hill, CA

[Business] SMC D3G Dropping internet for 1 minute at a time.

I've been having this issue with my Comcast Business Internet for a few months now. The internet works great for the most part but it will drop for about 1-3 minutes several times per day. This happens most often between the hours of 10am and 5pm, more often toward the middle of that time period, and never at night.

About a month or two ago we had a Comcast tech come over who couldn't find anything wrong, but did mention about bad firmware that had been pushed to the modems. He did a hard reset of the modem and it loaded different firmware. After that I couldn't log-in to the modem anymore, and had to call in to have them reset the password.

That did seem to help things at least initially but within a fairly short time the problems returned. It could be that the problems in-fact never went away - as the disconnections are sporadic enough that if I'm not on a VoIP call, I might not notice when it goes down.

What is perhaps the most aggravating about this situation is that the problems are so brief. The internet is always working fine when I'm on the phone with support, or when the tech is here, and obviously it's more difficult to fix something when it doesn't appear to be broken...

But even with the internet only going down for a minute at a time, that is long enough to drop VoIP calls, wreak havoc with the VPN, etc.

I have a tech coming out tomorrow, 12-4pm, but I'm not exactly optimistic that the tech is going to be able to solve the problem, since he couldn't solve it last time. Is there anyone that has had a similar experience who could point me in the right direction to see what might be causing the problem?

I'm using firmware version: 1.4.0.49.7-CCR

Upstream power is 45.5dBmV on the 64QAM channel and 41.75 on the 16QAM channel.

Downstream SNR is ~35.9 across all 4 downstream channels

Downstream power is 1.6-1.9dBmV on 3 of the channels, and -0.3dBmV on the other

It doesn't *seem* to be a signal issue, and the internet works very well other than the brief periods of disconnect.

Whenever the internet disconnects, I can log into the modem and see it going through the reconnection process.



JohnInSJ
Premium
join:2003-09-22
San Jose, CA

Your modem logs should be showing any disconnect/range error/sync issue - they should be able to see your modem log (you can't, it's behind the other login we don't get)

Have the tech access the management account, and look at the modem log while you watch so you can have him explain to you what all the errors in your log mean
--
My place : »www.schettino.us


chimerax

join:2012-07-25
reply to GotNoRice

I have had similar problems but it is not a big issue. Mostly when modem gets overheated the connection will drop. There is no problem with your modem or firmware or your cables. It is a usual one. When you are not using the internet for a brief time or when your modem gets overheated the connection will drop for some time and then it will resume.



NetFixer
From my cold dead hands
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage
·Comcast

1 edit
reply to GotNoRice

Are you actually dropping the Comcast connection, or are you only not able to get IP connectivity to the internet? If you are actually dropping the Comcast connection, that will be visible in the status LEDs on the front of the SMCD3G, and in the status displayed in the Cable Modem status display page (if you are near enough to to the SMCD3G while the connection is down to see those symptoms).

If you are only losing IP connectivity, the problem may be that the "Disable Gateway Smart Packet Detection" check box is not checked in the "Firewall Options" page. I have seen that so-called DoS protection feature cause more problems than a real DoS attack. The symptoms are often that you will lose IP connectivity to the Internet (and sometimes even to the admin pages in the router) for several minutes at a time (not unlike what you seem to be describing). It is so sensitive, that just normal Internet noise will trigger it, and I have seen something as normal as multiple video streams also trigger it.



--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.


GotNoRice
Internet Cynic

join:2001-12-04
Pleasant Hill, CA
reply to GotNoRice

Well the tech came over, and couldn't find anything wrong. Every test he did basically came back as perfect. He then said that the behavior I described means it is likely something on my end.

I'm not sure I understand how something on my LAN, behind NAT, could cause the Cablemodem to reconnect. He claimed that it's probably my router and out of date firmware, but I'm running the latest version of m0n0wall on a system with an Intel processor, intel motherboard, and an intel dual port Pro/1000 MT adapter. All pretty rock-solid stuff really. My connection to the modem is never disrupted, and I can clearly see it reconnecting until the connection comes back.

One thing I've never liked is how there is no way to disable the onboard router in the D3G with a dynamic IP. I have to have my router set as DMZ in the D3G. I'd like to take that out of the loop. I think I'm going to get an SB6121 and see if that does any better.



GotNoRice
Internet Cynic

join:2001-12-04
Pleasant Hill, CA
reply to GotNoRice

I ended up replacing my D3G with a SB6121, but even having eliminated that double-NAT situation, the problem is still there. SB6121 logs are a bit more descriptive, showing tons of T3 timeouts and T4 reboots. Example:

quote:
Aug 08 2012 03:08:24 6-Notice I401.0 TLV-11 - unrecognized OID;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 08 2012 03:08:24 5-Warning Z00.0 MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13 6-Notice N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Aug 08 2012 03:07:38 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 08 2012 01:53:18 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:27:52 6-Notice I401.0 TLV-11 - unrecognized OID;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:27:52 5-Warning Z00.0 MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:20 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13 6-Notice N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:26:57 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:26:27 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:26:27 3-Critical R06.0 Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:26:27 3-Critical R03.0 Ranging Request Retries exhausted;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 18:26:26 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 17:04:14 6-Notice I401.0 TLV-11 - unrecognized OID;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Aug 07 2012 17:04:14 5-Warning Z00.0 MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:22 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:13 6-Notice N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=X:X:X:X:X:X;CMTS-MAC=00:01:5c:24:b2:86;CM-QOS=1.1;CM-VER=3.0;
I'm still not quite sure how something on my LAN could be causing the modem to reboot, as the tech implied, but I went ahead and rebuilt my router anyway. I was running m0n0wall and switched to PFsense (something I'd been wanting to do for a while anyway) and put in another dual-port pro/1000 server adapter, but it didn't fix the problem either.

I'm really running out of ideas on what could even possibly be the problem, at least when talking about things under my control.


NetFixer
From my cold dead hands
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage
·Comcast

If your SB6121 is rebooting, it is not a problem with your LAN connections.

You need to make Comcast fix the problem. Even if the problem is with your internal coax cabling, Comcast should fix it for a business class customer (although you may get a bill for it).

If you are not able to get Comcast support to do anything for you (are you calling the business class support number 800-391-3000?), I would suggest opening a thread in the »Comcast Direct forum.
--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.



GotNoRice
Internet Cynic

join:2001-12-04
Pleasant Hill, CA
reply to GotNoRice

Yeah I'm going to pursue it for sure, don't really have much choice. I've had techs out twice so far, but once they plug my line into their tester and everything comes back as "pass", they seem to switch into "it must be the customer's problem" mode. The random nature of the disconnects mean it's usually working fine when the tech is over. They say that it's hard for them to diagnose the issue when they don't see anything wrong, and I sympathize, but something clearly is wrong.

About maybe 6-7 years ago I was having issues with low SNR (~29) and high upstream power levels (53+) and they ran a new cable from the street. Ever since then my signal levels have been basically perfect. My signal levels are still very good, ~36 SNR and less than 42 upstream power level - so I think the problem is something else but who knows?