Reply with External DNS IP's with Internal LTM VIP's

TJ,

F5 DNS has a feature that seems to solve your issue. When defining the servers in DNS, you have the option to set a Translation Address and a Destination Address. The destination address is the address returned upon a DNS request whereas the translation address would be the actual IP that is checked for health monitoring. This allows you to have two IP addresses associated with each server, one for internal use (pre-NAT) and one for external use (post-NAT).

Here is some helpful documentation on how it is configured.

Hope this helps.