We have 2 Windows 2008 servers. Both are domain controllers and global catalogs. Exchange 2007 (8.1- 240.6) installed on one of the DCs. Everytime we reboot the non-Exchange DC, Exchange stops working. Why isn't Exchange using the DC it's on to continue to work? Under the Server Properties->System settings, the current DC and global catalog list only shows one server - the one Exchange is not on. How do I get the Exchange server to use itself when the other DC is offline?

Is Exchange + DC also has Global Catalog role? If not, make it GC but however.... Exchange Server is not recommended to install on DC/GC. This is normal behaviour or problem when Exchange is installed on GC/DC and DSAccess/DSProxy component fails to failover to second DC/GC when first one goes down. If possible, suggest you to install Exchange server on a member server, move Exchange data and uninstall Exchange from DC. List of side effects when you install Exchange on DC/GC is given in this article. Exchange resident on domain controller that is not a global catalog server http://technet.microsoft.com/en-us/library/aa997060.aspxAmit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

Since both DCs are GCs; 1. I recommend to check ifan alternateDNS server is available while the DC1 is being rebooted.Check the DNS server has correct RRs (Alias & directory-services related) for DCs/GCs & Exchange server itself.2. Check Exchange server's TCP/IP configuration and DNS IP address order & recheck the IPs.3. Check app events for evenyt ID 2080 & other events from source 'MSExchange ADAccess'. Increase diagnostic logging for this counter could help.4. Check DSAccess property tab for the exchange server. ensure it is the default 'Auto' and not manually setup.5. Try restarting Exchange services (MS Ex AD topology svc / system attendant / service host) and check if exchange starts workingNote: Incase the Exchange DC was recently configured as GC; ensure to reboot that server once.6. Check for any AD replication issues