Slow DNS forwarding issues

[Haploe79]

I administer a network with a basic ISA RRAS setup to connect about 30-40 computers to the internet. The problem I've been having lately is that dns is taking FOREVER to resolve names across the internet now. Internal names resolve fine, and the dns servers themselves will resolve very quickly if you are logged into them.

Weird thing is, I tried installing dns on another machine thinking the other was overworked and it went very fast....for about a day, and now its slow again. This all leads me to believe it has something to do with the dns cache, but both servers are using default settings. I hope someone can help me out with this as when it gets bad my clients time out and don't resolve at all!

Setup: 2 dns servers, both ad integrated, both with forwarders enabled to the 2 isp dns servers. Both machines going through a single isa, though I've tried directly connecting one dns to the internet and no improvement. Traffic through the isa seems fine and still able to transfer very quickly(once you actually resolve the name)

 

[sgscit]

At the client, does an ipconfig/renew fix the issue for a short while?
If yes, next time it occurs does an ipconfig/flushdns fix the issue for a short while?

Do you have a server for your private (internal domain)?

How are your forwarders set up?

Do you have internal domain server high or low on the list of forwarders?

If your internal dns server is the root server (.) of your internal domain it may be fielding the requests and as it cannot use forwarders (if set up as a root) be unable to find the address, and thus time out.

Have you used NSlookup to test the various DNS servers? Can you lookup names on each server?

Cheers

Pete

 

[Haploe79]

Ok, No ipconfig /release /renew does nothing, nor does flushdns. The dns servers I have do have the internal address, but no root. Forwarders are set up with just the 2 isp dns servers as entries. As for nslookup, both internals CAN resolve external names, but as I said they do it VERY slowly.