DNS forwarding failing

[localzuk]

I have an irritating problem where DNS requests do not seem to be getting forwarded by our DNS server.

 

We have our DNS set up to forward to 2 DNS servers - the LEA ones and the SWGfL ones.

 

When we have the SWGfL servers set up as the first server to forward to, all is well with accessing SWGfL services, but our LEA services all seem to drop off (ie. we can no longer resolve LEA email servers etc...).

 

If we swap them around, so the LEA one is first to forward to, we can resolve LEA services but suddenly all our SWGfL services stop working.

 

Has anyone got any idea why this is happening? It is driving me insane!

[localzuk]

Ok, answering my own question:

 

Windows 2003 DNS servers ask servers in the list for records, and if any of the servers in the list provide a response (whether that response is 'YES I HAVE IT' or 'NO I DON'T'), rather than a timeout, then the local DNS server stops looking.

 

So, it appears that the problem in our chain is our LEA DNS servers - they're responding with 'No, we don't have the address' rather than either timing out, or forwarding the request upstream themselves.