Cable Modem Problems - Frequent Disconnects

[PreachTru]

My setup:
Motorola SB4100 cable modem
Netgear WGR614v4 Router (newest firmware)

Cable comes from the wall and into the modem. Modem then splits off to the wireless router. My PC is hardwired to the router, and my wifes PC is using a wireless USB adapter. I have the router setup as a DHCP server and two seperate IPs assigned to the respective computers. Both PCs are able to pull down an IP via DHCP from the router.

I used the EXACT same setup at my apartment without any problems. When I moved into my new house about a month ago everything worked fine, and then about 2 weeks ago everything started crapping out on me.

Both computers are affected by the problem below.

Problem:
My net connection dies randomly and quite frequently. Sometimes it will come back in a few minutes, other times it will last for hours. Resetting the cable modem and/or router does not fix the issue.

I called Comcast and they said there were no issues in my local area, and they were also completely clueless as to what the problem could be. A technician is coming out on Monday, but I am afraid it will be working when he/she gets here and they will just say it is working fine and leave me with the problem still.

I can't check the lights on my modem when I experience the problem because I painted the modem black about 4 years ago (it is pretty old now). Could it be the cable modem is going bad?

I checked the logs on my cable modem and I see some things that are alarming to me. This error is the most common error in the logs:

************ 5-Warning D3.0 DHCP WARNING - Non-critical field invalid in response

Here are some others...

************ 4-Error D530.8 DHCP - Invalid Log Server IP Address.
************ 5-Warning D520.2 DHCP Attempt# 1 BkOff: 5s Tot DSC:1 OFF:1 REQ:1 ACK:1
************ 3-Critical R2.0 No Ranging Response received - T3 timeout
************ 3-Critical R6.0 Unicast Maintenance Ranging attempted - No response - Retries exhausted
************ 3-Critical R5.0 Started Unicast Maintenance Ranging - No Response received - T3 timeout
************ 3-Critical R2.0 No Ranging Response received - T3 timeout
************ 3-Critical R7.0 Unicast Ranging Received Abort Response - Re-initilizing MAC
060813153621 7-Information H501.2 HFC: Shutting Downstream Down
060813153621 2-Alert T507.0 Received Async Error Range Failed
060813153621 3-Critical R7.0 Unicast Ranging Received Abort Response - Re-initilizing MAC
*********** 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing
************ 8-Debug T509.0 Acquired DS with status NO FEC lock, DS Freq 105000000, US Id 0
************ 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing
************ 8-Debug T509.0 Acquired DS with status NO FEC lock, DS Freq 99000000, US Id 0
************ 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing
************ 8-Debug T509.0 Acquired DS with status NO FEC lock, DS Freq 93000000, US Id 0
************ 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing
************ 8-Debug T509.0 Acquired DS with status NO FEC lock, DS Freq 855000000, US Id 0
************ 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing
************ 8-Debug T509.0 Acquired DS with status NO FEC lock, DS Freq 849000000, US Id 0
************ 3-Critical T2.0 SYNC Timing Synchronization failure - Failed to acquire FEC framing

 

[Ken90630]

Next time this happens, pick up the phone immediately and call Comcast. Ask the rep to do a "ping" test on your modem and any other tests he/she can do remotely. That might enable you or him/her to identify the prob.

Sorry, I don't know much more than that about networking and/or connection issues. FWIW, I have Comcast and rarely have any problems (other than the ridiculous bill at the end of the month). If I were in your shoes, I'd ask the rep to replace your modem when he/she comes over tomorrow -- if you ask nicely, they'll prolly just give you another one.

You might also try taking your router out of the picture by directly connecting at least one of your computers to the modem. Run it for awhile that way and see what happens. Oh, one other thought: Is it possible one of your neighbors could be "mooching" off your wireless connection and stealing your bandwidth? I hear about this happening all the time, although I don't know if it could cause the signal to be cut off entirely. Since you just started having these probs after moving into your new house, maybe .... Just thinking out loud.

Good luck.

 

[Lord Evermore]

More than likely this is an issue with the cable signal. It's possible for it to be too strong which can cause disconnects, in which case the tech can put an attenuator into the line to drop the strength a bit. Or it might not be strong enough.

I think you can ignore the DHCP error message, since DHCP only applies when the cable modem is attempting to regain an IP address. The timing synchronization failures and no FEC lock messages, which also reference the DS frequency (downstream) also make it seem like it's having trouble aquiring a signal.

There may have been changes outside your apartment, outside your building, or back at the headend that have affected the signal quality. Somebody might even have spliced into your cable to get free TV for themselves.

Painting over status lights is, frankly, dumb. Scrape the paint off them so you can actually troubleshoot the problem. Most likely your ONLINE or SYNC light or whatever it's labelled will be flashing or orange or whatever indicates a problem on your model.

 

[corkyg]

I have Comcast cable. It is generally, excellent, however, about once week I lose the connection completely. It is not the cable modem (Motorola SB-5120) most of the time - it is my Netgear router (WGT-624). Comcast changes their IP about once a week (Thursday or Friday), and the router doesn't pick it up. So, I just unplug it and replug it (power) and voila! Back in business.

Once in a while, there is a problem, so I call Comcast, and usually in a few minutes get a tech somewhere in the USA. They ping me, and if that doesn't work, we walk through recycling the modem.

One time, my call caused them to discover a local line break they didn't know about. Some contractor cut a fiber-optic cable. Took about 3 hours to repair it.

Milord is right - those LEDs are essential to determining what is right and what is wrong. Clean 'em off!

 

[Mutilator]

I would suggest checking the modem status again and getting the noise ratios and comparing them to what's normal at dslreports.com. And something you might want to keep in mind when/if you see the tech - "intermittent sync"

Could also try connecting a PC directly to the modem w/out the router and see if it still happens... it should if it's an intermittent sync problem.

 

[PreachTru]

I should have mentioned it earlier... but I have already tried a direct connection from my PC to the cable modem. The same problem still happens. So I believe I can eliminate the router as a possible problem in this situation.

 

[TeeJay1952]

I had a cable connection that would drop in the Morning around 8 AM. After 4 - 5 "Visits" from Comcast they figured it was the sun melting ice and the water dripping on an unsecured connetion.

 

[PreachTru]

It seems that a splitter was the cause of the problem. I had the cable connection coming out of the wall and running into a two way splitter. One cable then went to my cable mode, and the other cable to my television in the same room. With the splitter hooked up it would drop my channel power to -7dBmV. With the splitter removed and the cable modem connected directly to the outlet, the channel power is -2.8dBmV.

Just to be sure it wasn't an actual problem with my old Surfboard 4100 modem I purchased a new D-Link cable modem. Download speeds are more consistent and noticeably faster with the D-Link over the old Surfboard.

 

[corkyg]

Darn! I should have mentioned that. When Comcast p[ut in my cable Internet, they did not change the splitter, but used the existing TV splitter. That caused many probs - and they returned to fix it. A different but more knowledgeable tech knew right away what the problem was - and the right splitter solved the whole thing. I still have to recycle the router about once a week when Comcast changes IPs. But - that's easy.

Glad you got the splitter fixed.