router or cable modem problem?

I have a linksys wrt54g connected directly (wired) to a desktop and wireless to 2 laptops. I actually have no problem with the wireless internet connection dropping or anything like that. My problem is the desktop gets crazy packet loss (usually around 50%) whenever the router is connected. If I take out the router and connect the desktop directly to my cable modem, the problem goes away. I RMA'd the router with linksys and just received the new unit today, with the exact same problem. Before the linksys, I had a dlink router that also had the same problem. Could it be something wrong with my cable modem even tho it works perfectly fine when there's no router connected? If so, how can I get my ISP (Comcast) to replace my modem?
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More about router cable modem problem
  1. sounds like a problem with the computer NIC or the drivers for the NIC. You might want to try reinstalling the drivers for it.
  2. Ok, my mobo has 2 built in NICs. One I guess is the nvidia generic one because my mobo chipset is an nforce4. That was the one I was using with the packet loss. This morning I switched the ethernet cable to plug into the other one, a Marvell Yukon. It still seems to be having the same problem. I tried googling and going to nvidia and marvell's website and couldn't find newer driver versions than what I already have.
  3. Try lowering your MTU in the router. Generally found under advanced setup. Or go to they have a utility to help determine the correct size for your setup. Or try 1492 for a starting point.
  4. you might also try simply running the Windows network wizard and let windows make its settings anew. sometimes this will handle problems and fix network settings that somehow got fouled. for Win XP you can find the network wizard in the control panel. for win 98, go to START, RUN, type "inetwiz" and then follow the prompts
  5. Try a new network cable.
  6. I did the ping -f -l thing that's on to find my ISP's max MTU, and it's currently set at 1400. Each router came with a different ethernet cable that I've used each time. I'll give the windows network wizard a shot and update.
  7. Tried the network wizard, no help. Then next day it fixes itself automatically. Works perfectly fine for about 2 days, now it's back to the same problem.
  8. Are you doing anything unusual in the router? Does the problem exist if you reset it to defaults? Have you checked the error log on the router? Do you have any kind of security software installed on the wired computer? Does the wired computer have any other network interfaces besides the two ethernet ports?
  9. I'm not doing anything unusual to the router, it's set up pretty normally. Problem still exists if everything's on default. I have McAfee on my wired computer, and only the 2 ethernet ports.
  10. I'd try uninstalling or disabling mcafee. Not that I think it's the problem, but you never know. If that doesn't work, download and burn a copy of Knoppix to see if you get the same problem running through that. If you don't then you can be pretty sure it's something to do with software you have loaded in Windows.
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