I have two dhcp servers, one is Windows 2003 Server and the other is a DHCP Server that's on our firewall. I've set up the firewall dhcp as a backup:
- Split Scope - Windows DHCP (192.168.1.1 - 192.168.140) / Firewall DHCP (192.168.1.141 - 192.168.255)
- Microsoft Release DHCP Lease On Shutdown is set on the Windows DHCP Server (to release IPs at shutdown so it's quicker to grab from backup dhcp)
My question is should I put our internal DNS (for our AD domain) as the first DNS in the firewall's DNS settings (which has our ISP's DNS)?
This is in case just the DHCP Server in Windows goes down on the server but all else is functioning so users can still get to resources on the server. I have forwarders on our internal DNS to our ISP. I don't know how long it takes for a dhcp to look for their second dns (in case the entire server is completly down).
Also, should I place our ISP DNS as secondary/third DNS on Windows dhcp server - currently I only have our Windows DNS listed.