One Computer Will Talk to the Router But Other Two Computers Won't Talk to the Router

Reader James Biddle wrote to ask for help with a strange networking problem:

I ran into a unique problem that has defied the experts so far.
I have three computers hooked to a router. One day two of the three won't connect to the internet via the router. They will on direct connect.
On the older computer, I decided to install Ubuntu to see if that would change anything (thinking the issue might be related to the os--it had Xp when this problem raised its ugly head).
No luck. Nothing appeared to be wrong in the set up (net working).
Like I said all three run on direct connect.
The only computer that works via the router is my XP Pro machine (about two years old. My new Gaming machine using Vista) with a quad core is one that quit working.
The other machine is about 4 years old runs Ubuntu.

What would cause two out of three computers NOT to recognize the routers. I have substituted three routers and a hub all with the same dismal results.
HELP!

Thanks, and love the newsletter and the web site.

I wrote back to James to give him some suggestions on possible solutions.

One trick that you may have tried, but didn't mention. Computers and routers remember the MAC address at the other end of the wire. Sometimes you have to power all the computers and the router down, then power the router on, then power the computers on.

You would definitely have the problem with a hub, as your ISP is probably only assigning one IP address from your cable or DSL modem.

With a router, you can have a similar problem if you have the upstream cable connected to a regular LAN port on the router instead of to the WAN port on the router. The WAN (wide area network) port should be connected by Ethernet cable to the cable or dsl modem. The individual computers should be connected to LAN (local area network) ports on the router.

Yes to all you questions. They are hooked up correctly. They had all been working. Then one day this happened. Hence why I replaced the router. My computers are powered down at night. I did recycle both router and cable modem. I spend hours and hours on the phone with the cable company and the router (DLink) people. All agreed, that if one computer worked, then the router and cable modem work. The two other computers work ok on direct connect. But out of the clear blue won't go thru a router. I've tried three different one with the same results. I even hooked up a wireless card to test one of the computers and still nothing.

None of the techs I consulted can explain it. I had one tech out her for five hours and nothing he could do would make the computers see the router (other than the one). We even plugged them in one at a time to see if that would work. Nada. It's really baffling to say the least. This is the first computer problem that has ever defeated me.

Unfortunately, I don't have another solution for James. If you have a suggestion, please post your suggestion as a comment in my blog, send it to me via the Contact link at the bottom of the page.

Copyright © 2009 Terry A. Stockdale. All rights reserved.