Linksys Wireless Router and Dropped Cable Modem Connections

Which flavor (version)? Which firmware?

How do you know the problem is the cable modem? Do the lights show it as down? Did you have Comcast check the status of the cable modem?

The usual problem is the crappy firmware in the WRT54G, not the cable modem. Upgrade to the latest firmware version. If that does not help, switch to DD-WRT (build 13525) if you have a compatible model.

SURFBoard: Software Version: SB5120-2.19.0.16-SCM00-NOSH Hardware Version: 4 MIB Version: II GUI Version: 1.0 VxWorks Version: 5.4

LinkSys: Firmware Version: v8.00.8

I don't know the modem is the problem? Assuming, based on ability to stay on line with the router out of the picture (pc plugged in to modem directly)

Light do go off, when it goes off-line. Seems to go through a series of resets???

I did once, and they seemed to indicate that it appeared my modem was on-line and that they could see it...

Upgrade to the latest firmware version. If that does not help,

I'll double-check the latest version of the firmware, as well as looking into DD-WRT...

Thanks for the quick response! Todd

had the same prob (balt area, comcast, cable internet, linksys wrt54g, dropped connectivety now and then)... in my case it was power to the wireless router (summer, AC power, spikes and low voltage when ac's kicked on, not bad enuf to make clocks flash 12, but bad enuf to mess up my wrt thing) happened to have a battery backed up ups handy, used that instead of the wall wart, problem solved

simple free test, to help determine the culprit, next time it is dead, unplug the wall wart (from the power plug on the back of the wrt, not the wall) and plug it back in again (don't do anything else) if it works again, you have narrowed it down to transient voltage fluctuations on the ac line/funky wall wart thing

from what you say above, it isn't actually the cable modem itself (since you can wire direct to your pc and it works/doesn't drop), so why not try something free, to help narrow it down?

ps, newer wap/routers have better powerline filtering, and don't do that... i'd suggest give a try to the free/simple test, and if needed just get a new wap/router (new linksys/cisco about $60 at walmart)

Maybe your provider is throttling your usage that way.

If you are being a bandwidth hog on your neighborhood's last mile, they should do something about it.

read what you wrote.... " >> I work from home, and end up plugging the cable modem directly into my

ergo, your cable modem is *NOT* dropping out, so it's the wireless router that does.... don't understand how you can even wonder which (cable modem or wrt) it is, when you state very plainly it (cable modem) works.... if it was the cable modem, it would drop out when connected to your pc too.....

Interesting... I'll give that a try. Thanks!

I'm not ruling anything out. It seems to occur, though, when nothing else is using the net.

Might be worth a call to see if there is any throttling on their side, taking place. At least I wouldn't continue thinking I had hardware issues...

it would drop out when connected to your pc

I don't believe I ever suggested it was the cable modem. I actually have suspected it to be the wrt all the time... I simply asked, "Is it the wireless router? Is it the cable modem? Is it a combination of both???". I was mostly wondering if there was a compatibility issues with the modem and the router.

Thanks for you input though! I'll test the power, as you suggested above.

Best Regards, Todd

You don't mention which lights go off, which would be very helpful to know.

You can also check your cable's signal levels by pointing your browser at http://192.168.100.1/signal.html The three key areas to note are - Downstream Power, which should be between +-15dBmV, with +-10dBmV being desirable, - Downstream SNR, which should be in the mid to high 30's, with higher being better, - Upstream Power, which will probably be over 45dBmV but should be well below about 55dBmV.

Having said this, I agree that the primary issue seems to be the router, not the modem, going by what you've provided so far.

That resets the router, so you've only narrowed it down to the router, not the power adapter. The only way to narrow it down to the power adapter is to replace it with a better power adapter.

thecablemodem, it would drop out when connected to your pc

You said, "... the cable modem seems to get knocked off-line"

That sounded like you thought it was a cable modem issue. Still does. Part of the problem is that your description was and is vague.

Unlikely -- throttling is usually much more sophisticated than that.

Divide and conquer. You have 5 different points of failure and you're testing them all at the same time. There's the cable modem, the WRT54G, the wireless connection, and interconnecting cables and coax. There might also be a problem with your test computer, but I'll assume that it happens to all machines on your network. With several disconnects per hour, this should be easy.

First take the wireless out of the picture. Find a CAT5 ethernet cable and plug it directly into the WRT54G. If the problem magically goes away, you have a wireless problem. It could be bad router. Please disclose the hardware version of the WRT54G. It's on the serial number tag. v5 and v6 drove me nuts with flaky operation. It might be old or bad firmware. If you have another model router available, it's easy enough to substitute and retest.

It might also be wireless interference from other users of the 2.4Ghz band. It's not just other wireless networks that cause problems. There's a wide variety of 2.4GHz RF emitters that can cause problems.

Lately, 2.4GHz wireless security cameras are my main headache. In the past, it was cafeteria microwave ovens and RF induction heaters that drove me nuts.

Next, check or replace the CAT5 cable that's run between the cable modem and the WRT54G. If it looks home-made, replace it.

Next, plug your computer directly into the cable modem. No router and no wireless. If the problem magically goes away, there's something wrong with WRT54G. Incidentally, check the WRT54G power supply for overheating. I've had a few of the linear (non-switcher) variety die on me. Before they go to no-output mode, they became intermittent causing numerous unscheduled reboots. Watch the lights and see if this is the problem.

If problems persist when plugged directly into the cable modem, it's time to check the coax cables. I recently fixed a motel wi-fi system by simply replacing all the crappy coax cables (with miserable connector crimps) and reconfiguring the maze of power dividers. Go to:

and you might see the signal levels go up and down as you thrash on the coax cables.

Don't assume your SB5120 is perfect. I've replaced a few of those (usually with a later model SB5101) and fixed performance and disconnect problems. Check the numbers on the signal level page, especially the line levels and SNR.

After that, it's time to call the cable company. Last year, I had difficulty convincing them to make a service call until I walked over to the connection box, and found that it had been rammed by a vehicle and was now full of water.