Networking problems help please

[LinuxRandal]

I am trying to diagnose a cable/internet connection problem. I haven't had any issues for the several years I have had it and in the last couple of weeks, I have had to use other peoples access. My modem (Motorola SB3100) has four green lights that all light up and one yellow/talk light. It would give the connected firewall an ip address, and that would get broken about 14 minutes later and not be seen again without both being rebooted (sometimes not for hours).
I disconnected the cable modem from the firewall, and hooked it directly to my normal use pc. I tested all cables (they all work and I can see my internal network but not out), and the same issue with the computer as with the firewall (about 20 minutes maximum online, average a DAY, then not seen again).

I am needing a way to test the modem itself (if any) to see if it is actually going bad (network port) and not allowing anything after it to get an IP. I have tried (once) comcast support, and they only read from a script (got me online for then hungup and I was off again two minutes later).

Pings keep up till it breaks the IP, traceroute will work until I loose my IP.

[LCHIEN]

I am trying to diagnose a cable/internet connection problem. I haven't had any issues for the several years I have had it and in the last couple of weeks, I have had to use other peoples access. My modem (Motorola SB3100) has four green lights that all light up and one yellow/talk light. It would give the connected firewall an ip address, and that would get broken about 14 minutes later and not be seen again without both being rebooted (sometimes not for hours).
I disconnected the cable modem from the firewall, and hooked it directly to my normal use pc. I tested all cables (they all work and I can see my internal network but not out), and the same issue with the computer as with the firewall (about 20 minutes maximum online, average a DAY, then not seen again).

I am needing a way to test the modem itself (if any) to see if it is actually going bad (network port) and not allowing anything after it to get an IP. I have tried (once) comcast support, and they only read from a script (got me online for then hungup and I was off again two minutes later).

Pings keep up till it breaks the IP, traceroute will work until I loose my IP.

sounds like you need a new modem, but you probably already figured that out.

After I came home from Ike, my internet wasn't working. No lights on the modem except power and enet. I figured the modem was broken, AT&T (DSL) tech help was worthless, they kep checking the line it was ok, the next guy told me service wa s out and it be back on later. Finally (and fortunately) I dug out an old modem and subbed it - that worked. No help to AT&T tech support.

[bmyers]

Do you loose the "online" light on the modem when the problem is present?

I had a similar problem a few weeks back. I would just drop off the face of the earth and the modem would loose connectivity.

Turned out that the modem was fed from the next room over and the cable line was under the leg of a recently moved dresser. Crushed the cable and left me with a flakey connection.

Try connecting the modem as close as you can to the source of cable in your house and see if the connection stays up. Don't use any T's upstream from your modem.

Bill

[cgallery]

Try connecting the modem as close as you can to the source of cable in your house and see if the connection stays up. Don't use any T's upstream from your modem.

Bill

+1

If you can disconnect any splitters and feed the modem with an unsplit feed from the cable company (right as it enters the house), you'll be able to determine whether the modem is bad (sounds pretty likely) or if you don't have enough signal (this can happen when neighbors change and the new neighbor adds splitters galore).

The cable modem requires more signal than the TV. So it is possible that TV's would still work fine, but that the cablemodem would still blink out.

[LinuxRandal]

No loss of the online light (lets see if this will post), and it is the first thing in. I didn't even have the tv section hooked up for years (only did it recently due to the signal stuff).

Going to have to find out what modems run, and what works with Comcast today I guess. So my internal assessment of the modem sounds correct (I was SO hoping I was overlooking something).

[bmyers]

If you're not loosing the online light then comcast tech support can test the modem and look at packet discards, retries and other badness. They can tell you if the modem is on it's way out.

If they're not seeing errors, your problem is most likely something else. Make sure you're using DNS settings that they tell you to use. Things do change..


Are you wireless? Another problem I had was that most of my setup is wireless. A shabby old 2.8 Ghz wireless phone in my house was booting me off the network when it was in use. THAT was a PITA to find...

Pings keep up till it breaks the IP, traceroute will work until I loose my IP.

Ping to what? www.yahoo.com or to your firewall/gateway?

Bill

[LinuxRandal]

If you're not loosing the online light then comcast tech support can test the modem and look at packet discards, retries and other badness. They can tell you if the modem is on it's way out.

If they're not seeing errors, your problem is most likely something else. Make sure you're using DNS settings that they tell you to use. Things do change..


Are you wireless? Another problem I had was that most of my setup is wireless. A shabby old 2.8 Ghz wireless phone in my house was booting me off the network when it was in use. THAT was a PITA to find...



Ping to what? www.yahoo.com or to your firewall/gateway?

Bill

The addresses used were known ones. Comcasts local gateway, DNS, I believe one of the early ones I tried was google (when I figured a glitch).

As far as I know on the modem, they can only determine what is going on between it and them, as they only have a connection on the cable side (correct or not?). I believe the problem likes between it and the outbound networking port, internally (with my luck something like a cold solder joint that failed).


Edit, this morning, I have had to reboot the modem and nothing else, 3 times so far.

[JR]

Just take that modem over to the Comcast office for a swapout. They'll have a customer service window to deal with that kind of interaction.

JR

[Mr__Bill]

Comcast can talk to your modem and diagnose problems and even download new firmware to it. Set the DL speed and all that stuff. That is, if you get a tech person who is not too busy and know the what and how.
good luck

bill

[wbsettle]

And I thought my 4100 was a dinosaur. In service since 08/01. Tempted to take it in for a swap every now and then "just because".

Anyway, as others have said, assuming Comcast works like TWC, just take it into the nearest office and swap up a couple of generations. You've earned it.

A quick Google for the 3100 suggests that network speed increases over the years may not make it happy. Remember, when that thing was issued, 1.5Mbps was the max speed for most services...now the "standard" TWC Roadrunner package is 7Mbps. It's possible Comcast did a recent upgrade in your area that's finally taken its toll on the poor thing. Or it just broke.

If you own the modem, not Comcast, Best Buy/Circuit City usually have cable modems for purchase that are free after rebate. Even without rebate, the current SurfBoard 5101 is $80 @ CC. As yourself how much you've already spent in time trying to fix this relic from the Dark Ages.

Barring all that, if you haven't already, you can peek inside the modem and see what it has to say. Point your browser at 192.168.100.1. The 4100 has a log file of internal activity as well as current status pages. Couldn't find full internal info for the 3100, but what screen shots I did find looked just like my 4100 display.

-Brent

[LinuxRandal]

Update, still using elsewhere for internet.

The 3100 is OWNED by me, and my father also bought one but he moved about 6 months later. I went over and we found where he stashed his, brought it home, called them and hooked it up. After they entered it, all the lights came up, I received a valid IP, and two minutes later no connection and looking for a new address. The logs showed that all night (not modem logs).
I rebooted both this morning (after letting them set off for about 15 minutes), and same thing.
I am going to have to call them later. The ONLY part of my stuff that hasn't been changed or checked, is the cable between the modem and the outside (about 10 feet). From looking online, I think either someone has spliced into the line again (knocking something out of phase, like a neighbor did years ago), or something is out of spec, and causing interference (which would be picked up by their plug in tester, but maybe not their online diagnostics).