A few days ago I had severe network issues (which are now resolved) but has left me with DNS issues I can't get my head round. I have a Windows 2008 R2 domain, Exch 2K7 CCR, EMC SAN for files, and Windows 7 clients.

From my PC I can ping everything and access all network services such as file and print and exchange etc. This is the same across the network and all users are ok.

My exchange server (E1 passive node of the 2) has stopped recieving data from the active node (E2) as it can't find it.

I can ping both domain controllers from either exchange server by name and it resolves the IP address when replying. I cannot however NSLOOKUP from either exchange server as it can't find the primary dns server (which it can ping!!)

I did a dcdiag on the domain controller DC1 and the results were that it couldn't find itself!!!!

Many thanks,