Problem with Exchange mail flow when DC is down
Posted on 2009-04-09
I currently have two W2K Domain controllers, DC1 (physical) and DC2 (virtual). DC1 is the primary DNS server, DC2 the secondary. I have an Exchange 2K server that is configured to use DC1 as primary DNS and DC2 as secondary. We're planning on decommissioning DC1 and replacing it with a new virtual DC (different name, hopefully the same IP if all goes well). We'd like to keep the same IP so we don't have to change all of our static DNS configs.
I've moved all the FSMO roles off of DC1 onto DC2. I've pointed the Exchange RUS services from DC1 to DC2. In the past, I was told that there was always a problem with taking down DC1 and having mail flow correctly. To test, I turned off DC1. I rebooted our Exchange server and even though all services came up OK, mail would not flow. As soon as I turned DC1 back on again, mail flowed successfully.
I didn't want to tinker with the DNS settings since it's still a production environment, but to me it seems like there is more going on. It should just fail over to the secondary DNS if the primary is down, so I don't know if that's the issue. Is there something I'm missing with Exchange and it's relationship to a "primary" DC? Outside of the RUS services, I've found no reference to DC1 in the ESM.
Any help would be greatly appreciated,