DNS Forwards no longer working
Posted on 2008-10-08
Weird one here, nothing huge I'm sure, but I'm swamped and wanted to give you guys a crack at it first...
We have a Windows 2003 Domain with our Domain Controller as our primary DNS server. The DNS handles our domain DNS and forwards requests for external domains to our ISPs DNS servers (in the same datacenter). This has been working fine for months, but last night DNS forwarding stopped working mysteriously. I look at the DNS server and everything internally is resolving properly, but external domains don't work. I tried to ping the DNS server from the machine and get a response:
Reply [IP OF ROUTER]: Destination host unreachable.
I telnet into our Cisco router and ping the DNS server and it works perfectly... I can also ping external IP address (ie the Public IP address of google.com). However, when I try to ping them from the server behind the router I get the same result.
I can't reboot the router until tonight, because incoming traffic through that router is still working properly (ie, email, OWA, etc) so taking those down would make matters horrible, and the DNS servers there aren't in use by our company at our office so no users are screaming...
Our routing scheme consists of a default route 0.0.0.0 [route of ISP gateway], so it's not really all that complex, and no changes have been made to the configuration of the router overnight. Any way to narrow down the problem to make my troubleshooting tonight easier?
As a side note, I DO have Remote Desktop Access into the servers in the datacenter, so I CAN change configs on both them and the router if need be...