DNS Failover

Good Morning All,

I have a question about DNS failover?

I have and internal domain, which has ‘Forward Lookup Zones’ to both the internal and DMZ zones. When the internal PDC goes down, I would expect that the secondary internal DC / DNS server would pick up the slack. What I am finding is that when I take the PDC off-line the other DC/DNS server is not picking up the slack. I have a TTL of 1 hour on both DC?s. With a Refresh Interval of 15 minutes, Retry Interval of 10 minutes, and expires after 12 hours. Is there some other issue / configuration setting that I am missing? Any advice will be greatly appreciated.

Regards,
Paul