I should start by mentioning that I rarely ask for help with issues as I am a PC Technician. I build computers, I write software, design web pages, etc. I'm the guy that fixes everyone's computer when it breaks. However, I've been having this really weird problem for the last couple days that even has me (my geek self) stumped. I have a network (wired with a router, not wireless) with a few computers on it. My main machine has been appearing to lose internet connection off and on. Like my connection to AIM will suddenly drop, can't load web pages, etc. I can not trace it to any repeatable event like running specific software or anything like that. It truely appears to be random. At first I thought maybe I was having network or ISP problems until I realized it was only the one computer. And I had direct IP connections going that continued to stay active when the internet connection seemed to be down. So naturally, I tried pinging some servers on the internet (by IP address) and they all ping fine. Can't ping host names though. Obviously some kind of DNS problem. The weirdest part is that if I leave it alone for a while, eventually it starts working again, no reboot or anything (though rebooting does fix it too). Eventually the DNS works again on its own after an apparent random relaxation time (lol). All of the other computers work perfectly. No drops, no DNS issues, nothing. I'm figuring there's some kind of problem with a DNS service that XP is running, but I thought I'd ask on here and see if anyone else might know before I start ripping my system settings apart. Maybe save some time. I've never heard of a problem like this that was specific to a computer so there's some kind of software problem going on. And I hate it (obviously)! Any help/ideas would be appreciated. Thanks!

I would first check hardware. Test the cable and NIC. You may want to try a different port on your switch if both of those look good.

Then double check the DNS settings on the PC in question and flush it's DNS cache (ipconfig /flushdns).

I considered the cable. I built the cable myself so I assume there's nothing wrong with it. I did use my cable tester on it and it came back fine. It seems like it got damaged in one section from my dog, but none of the wires were broken, just the jacket, and the line tester says all the nodes are fine. Plus the cable has worked fine for the last 2 months since I ran it. The next time the problem occurs I'll try that DNS flush to see if it helps. I've been up for 2 hours so far with no problems. Which is sorta bad, I'd rather the problem not fix itsself. lol I'll post again when it happens and I try the flush. Thanks.

My dad always used to tell me, "assume makes an ass out of u and me". I've made more cables than you can shake a stick at and that doesn't keep the odd one from having problems. Especially if there is damage to the outer casing. (I'm a network technician and pulling/making cables is part of my job)

What kind of cable tester? The cheap kind with blinking lights? They're not very good and can't really tell you if there's a short in the line anywhere. Try another cable that you know is working good and isn't damaged. There could be a short in it or damage to the actual wires you didn't see.

Don't forget to test the NIC and try another port on your switch.

Did you say you tried to ping the DNS servers? You can also search the internet for public DNS servers, then substitute these for your regular ones to see if it is indeed a DNS server issue.

98% of the population is asleep. The other 2% are staring around in complete amazement, abject terror, or both.

Well, it's happening again. I tried flushing the DNS, reacquiring the DHCP, I even disabled and reenabled the network card, and my other system still can not resolve DNS names. This makes no sense at all to me. It was working fine like 5 minutes ago. I actually was viewing CNN's webpage when it happened. Out of the blue for no reason.

Out of curiosity, what should be displayed when you do a ipconfig /displaydns ? Should that list your DNS servers? I'm wondiering because I flushed the DNS and then ran that displaydns and it shows a bunch of ad servers , IE www.adserver.com, www.cash2002.de, www.valuesponsor.com, etc.

I'm assuming that's not supposed to be there. I don't understand why it would be a random problem and not constant though. Any other ideas?

Curt R, yes, I have the tester that just blinks the lights to check for continuity. I normally wouldn't simply rely on that to assume the cable is fine, I'm assuming it's fine because most of the time it works fine. Even when it's not working it's basically working since I can still do everything else other than resolve DNS (including transfer large files over the network without any CRC errors). I've got another NIC in my hardware box, I'll see if I can throw that in to rule that out as a problem. And I will also test another cable just to make absolutely sure. I just doubt that's the problem. Either way, I will post here again with an update once I try those things...

I think I've resolved the problem. Not positive but I removed some forwarded ports that I set up on the router to allow incoming connections to my system and when I removed that it seems to have fixed it. I don't know whay that would cause this problem, but it seems to be what the problem was.

I have had the same problem on a number of computers. One desktop wired to a Linksys Router on a SBC DSL connection, and 2 laptops wireless to linksys, netgear, and airlink routers, using time warner roadrunner cable service. I can ping all the way through (loopback, network address, network gateway address, dns address (as reported by router), but tell it to ping "yahoo.com" and it can't resolve the host name. Different networks, different network cards, wired/wireless, different computers (home made desktop, Winbook laptop with Linksys wireless pcmcia card, fujitsu laptop with atheros built in wireless), different ISP's. The only common thread is WinXP SP2. Leave them alone for a while and they work, then all of a sudden they don't. Would love to see a post here directing me to some help.

Chuck Rudolphy
crudolphy@houston.rr.com