Hi
Just wanted to provide an update on this issue and close the loop.
While we haven't nailed down the exact lines of code causing the problem, we have at least been able to confirm that it is related to the way apache and glibc handle the configuration of the resolver.
We were able to confirm through adinfo queries that when firewalled off from specific DCs, the system migrated to the correct next available DC quickly and correctly, and that any of the system functionality we use outside of apache migrated correctly when the DC/DNS server was cut off.
We appreciate your help on this issue!
Thanks again,
Ryan