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Hourly disconnection problems with SB5100?

For a couple of weeks now I've been having a very weird problem: every hour, at the same time (:30 minutes past the hour for example) the net will go down for 30 seconds up to 20 minutes. The SB5100 shows no errors, the router (a 3Com 3CR860-95) shows no errors, the net will just be inaccessible. I've been running PingPlotter to plot the outages.

Now, I have found that rebooting the router will usually solve the problem for a couple hours, but since the problem occurs at EXACTLY the same time, regardless of when I reboot the router, I've been informed that it's likely not the cause. I have isolated specific PCs on the router and the problem remains. Generally, rebooting the modem has no effect.

The outages seem spaced by about 60 minutes and 10 seconds - what was originally happening at :30 minutes past the hour a while ago has slowly and very evenly worked its way up to :45 minutes past the hour.

I'm on Rogers in Ontario and the problem SEEMS to have been reported by at least one or two other users (

formatting link
), but they seem to have since dropped off the face of the planet and aren't any help trying to diagnose this issue. Of course Rogers tech support is useless.

Anyone have any suggestions? What occurs once an hour like that? Here's the current modem stats:

Downstream Value Frequency 615000000 Hz Locked Signal to Noise Ratio 37 dB Power Level -5 dB The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

Upstream Value Channel ID 1 Frequency 32496000 Hz Ranged Power Level 36 dBmV

(I seem to recall that the downstream power level used to be more around the

0/+1 dB level)

- Sunfox

Reply to
Sunfox
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The ISP is currently giving a lease time of 7 days (currently 7 days remaining). The router also gives a lease time of 7 days to PCs...

- Sunfox

Reply to
Sunfox

Have you done a thorough scan for viruses recently? -Dave

Reply to
Dave C.

Just curious, what is your dhcp lease time. Look to see if the lease duration is close to the times you see. No idea how to see the lease time in your router, and in the cable modem, look at duration and time http://192.168.100.1/address.htm

Reply to
Bit Twister

Hello, I just registered here, as I found this particular thread through google. I really hate to bump a thread that's 2 years old, but I am having the *exact* same problem as this guy described. This issue has happened three times in the past oh 6-9 months or so, and when it happens it's seemingly impossible to stop and lasts for weeks/months. It's driving me insane. I'm very close to taking this modem out Office Space-style. I'm willing to provide any information needed as well as follow any instructions you provide until my problem is fixed. Thanks in advance.

Here's what I'm working with:

SB5100 modem straight to computer (I was using a router but I got tired of having to power cycle it every day to restore my ip - when the modem can't renew the ip, the router drops all wan information).

My connection drops for about 15-30 seconds, every hour like clockwork. My windows event viewer shows this under system every time it happens:

"The IP address lease [my ip] for the Network Card with network address [my nic mac] has been denied by the DHCP server [comcast's dhcp server ip] (The DHCP Server sent a DHCPNACK message)."

My windows dhcp lease time, according to ipconfig /all is 2 hours. My modem apparently likes to check every hour. I cannot modify dhcp lease time in my modem's config page (192.168.100.1). In fact, the only things I can manually do in my modem's config are "reset all defaults" and "restart cable modem" (I've yet to use either as I just found the config page but I'm very tempted to reset all defaults).

Every so often (lately about once a day) when my modem tries to renew the ip, it stays in this ip-less state until I power cycle it.

These problems always start when something happens and my modem loses all signal (i.e. becomes untrained). When it comes back online, I get disconnected 60 minutes later, and so on, and so forth.

The first time it happened, after a few weeks, I reconnected my router which I had stopped using, and the router seemingly took care of the problem until it went away on its own.

The second time it happened, I waited a couple weeks before calling comcast tech support. The tech support guy sent my modem a reset signal and instructed me to use the 'repair' button under my 'local area connection status' dialog's 'support' tab. Problem solved.

The third and current time it happened, I didn't hesitate to call comcast and have them send my modem a reset signal. 60 minutes later I was still connected without getting dropped. The success was short-lived though, as 60 minutes after that the problem started again.

I use a third-party firewall. It doesn't matter whether or not it's running, the problem happens anyway. I also also use norton antivirus, with automatic updates and weekly scans. My computer is very clean and as secure as the firewall permits.

Please help me, I am extremely frustrated with this. Comcast tech support seems to think it's my computer causing the problem as I have a very good signal and my modem stays trained, but knowing what I know, I *highly* doubt it.

My next obvious courses of action if I can't fix this are to get a new modem (I can rent one for fairly cheap but I really don't want to), and to have a technician come out if the problem truly is on comcast's end.

Thanks, Trogdor

Reply to
Trogdor

From you browser, enter 192.168.100.1 to load the modem information page. Access the Signals page and post back the downstream and upstream signal levels in dBmv and the signal-to-noise ratios, if available.

Q
Reply to
Quaoar

As of this morning, my modem refuses to interface with my computer, to include serving its config page. Looks like I'll have to replace it. Thanks anyway.

Reply to
Trogdor

Don't throw that modem away. The Motorola 5100 and 5120 have very good reputations, and it may still be good. It it does turn out to be the culprit, I'd look into a possible ventilation problem.

*TimDaniels*
Reply to
Timothy Daniels

It appears that there has been a new release of the firmware for the SB5120. That is likely the case for your SB5100 also. My SB5120 had also exhibited the inability to load that Configuration Manager page yesterday even though all modem lights were normal. After power-cycling the modem, it came back and investigation of the log showed that Comcast had pushed new firmware.

Give power-cycling a try as your ISP might be doing the same thing. You might need to also power-cycle any router you have and possibly reboot to get everything to work.

HTH Bob

Reply to
Robert Heiling

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