The setup we have is as follows: 2 - Exchange 2007 CAS/HUB servers (Load balanced with NLB) 2 - Exchange 2007 Mailbox servers (CCR Cluster) A couple of weeks ago, I got warnings for event id 2105 & 2106 (MSExchange ADAccess) in the application event on one of the CAS/HUB servers. It eventually ends up causing OWA and Activesync issues. Here is the message: Process MSEXCHANGEADTOPOLOGYSERVICE.EXE (PID=1736). Exchange Active Directory Provider failed to obtain DNS records for forest. DNS Priority and Weight for the Global Catalog servers in this forest will be set to the default values 0 (priority) and 100 (weight). After rebooting the server, everything is fine and there are no problems on that server. A couple of weeks later, the same issue happens on the other CAS/HUB server. After rebooting this server, everything is fine and nothing is wrong with the other server. I have checked the DC in question and everything seems to be fine. Any ideas as to why this would be happening? It has only happened once on each server since they have been put in to production a year and a half ago. Thanks in advance for any help.

I have seen these kind of issues because of DNS reach problem. at the point of problem does DNS perfom good from problamatic servers.Best Rgds, Ashish | Unified Comunication | MCTS | MCITP | Please remember to select option "Propose As Answer" if solution work for you | My posts hold no assurances, no promises, and they measured no rights.

Yes, DNS appears to be working fine from the box at those times.

Please see the descriptions in the articles below Event 2105 Event 2106 As the issue has gone currently, it’d be difficult to prove the root cause since the system are working normally again Please run “DCDiag /v /a” and “NetDiag /v” to check the health of DC and connection to DC from the CAS/HUB servers Please run ExBPA against the CAS/HUB servers for health checkPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.