Client Dns Connection Times Out

[ChrisWanamaker]

This has been driving me nuts - and I've searched everywhere for a solution with no luck ...

 

A few weeks ago, we installed a new Server 2008 R2 box setup for DHCP, DNS and AD. At random intervals throughout the day, users will be unable to resolve domains that they were just on a few minutes prior. They get the "Diagnose Connection" screen in IE8. Everyone on the network is setup to get DHCP from the server and their primary (and only) DNS IP is that of the server as well.

 

When the problems with domain resolution occur and I do an NSLOOKUP from the client, I get the error message "DNS Query Time Out. Time Out Was 2 Seconds". I checked the server and I currently have the forwards setup with the Root Hints option unchecked and the timeout set to 10 seconds. After a few moments, everything goes back to normal and the internet begins resolving again.

 

DCDIAG returns PASS for everything ...

 

Any ideas where I should be looking and what I should be looking for?

[mmthomas]

When the ns queries fail, is it failing on just the clients, or both the clients and dns server? Does just the query time out or is it failing to connect to the ns server, too? Are you able to resolve names within the domain and only failing on external names? Are there any performance issues on the DNS server at the time of these problems (low memory, high disk usage, high proc, etc). Some possibilities: DNS server NIC is intermittently failing and then coming back online (would result in failures to resolve local names as well as external names), firewall (or router or internet connection) is intermittently failing to forward DNS traffic (local resolution would work and external would fail), intermittent failure of the ns server which you have set for forwarding (local resolution would work and external would fail; could be resolved by using root hints and not a forwarder). Check your server logs, too, for and DNS failures or hardware failures occurring at the same time.