I’ve got a very specific problem with my home network that I can’t seem to solve. I’m pretty savvy with a computer and I know a bit about networking but it’s definitely a weak spot in my knowledge, I’m hoping you folks can help me isolate the problem and decide if it’s a hardware issue, a software issue, a configuration issue or if it’s something I need to beat up Comcast over.
Here’s the Cliff’s Notes version:
I added a second computer to my network a couple weeks ago, a new laptop that connects to my network over Wi-Fi. Ever since I added it to the network my connection through both machines screeches to a halt when I run both computers simultaneously. Initially I assumed that I was just over taxing my bottom tier bandwidth package from my ISP. After doing so digging this appears to not be the case since the slowdown happens even when the second computer is online but doing nothing. The problem disappears entirely when I take one of the computers off the network. I visited pingtest.net and speedtest.net to evaluate and was able to determine that my latency was through the roof when running 2 PCs, returning ping times well over 3000 ms. My upstream and downstream speeds are consistently solid.
So, long story short, why would adding a second PC to a network cause my ping times to increase exponentially?
Here are the main players:
Desktop PC: Vista
Laptop: Windows 7
Router: Linksys WRT160N
Modem: Motorola Surfboard SB5120
What I’ve done so far:
Tried replacing my Wireless Router. I originally had a Linksys WRT54G that I’d never had a problem with and since the issue only seemed to crop up when I was routing both computers through it I assumed it was to blame. When I bypassed the router and connected to the modem directly things were fine. However when I connect the individual computers through the router both wirelessly and wired by themselves it works fine too. When I installed the new router the problem was identical. I spent the afternoon today on the phone with Linksys phone support and they couldn’t find a problem. They are sending a warranty repair for the new router but I’m almost certain it’s not the issue since the problem is identical between two different models of router.
I’ve called Comcast and tried trouble shooting the problem with them and it’s been no help at all. They reset the modem and basically created new problems. They claim that there’s no reason that 2 computers would effect their service like this but I’m not sure if I buy that. I’m not even convinced that their techs understand what I mean when I talk about latency.
I have a service appointment scheduled for tomorrow but I’m not optimistic since the guy will most likely determine that my signal strength is fine. If there is a service issue it probably has something to do with routing or DNS farther up the line.
I’m wondering if this could be a result of my cable modem going bad, but I don’t know enough about how networking and routers work to know if my cable modem would even see a difference when 2 PCs are routed through my wireless router versus one.
That pretty much sums it up. Anyone have any ideas why my latency would go up exponentially with 2 PCs online but be excellent with one? Is there any way that this is a issue with something Comcast is doing? What is the likelihood that I’ve gotten 2 different models of routers with the same issue? What should I ask the Comcast tech about when he comes? Are there any more tests I can do?