Big-IP DNS - LTM Design Clarification

For the user point of view, the GTM gives him the public IP, that he uses to connect to the LTM. The firewall will take care of the NAT, and the traffic will arrive in the LTM with the private IP.

The GTM will have a connection with the LTM, does not matter if via internal connection or via the Internet. Using that connection, the GTM will ask the LTM about the status of the virtual server, but will use the private IP.

So, it is transparent to the LTM, that there is a NAT. Because user traffic arrives with private IP, and GTM asks the status with private IP. On the other hand, GTM must know the private and public IP, so he can use the private when talking with the LTM and public when answering DNS queries from customers.