By default using SNAT forces the BIG-IP to replace the source IP address on requests it sends to the pool. The BIG-IP automatically undoes the translation when it responds back to the client to ensure the client accepts the response.
Could you provide more detail on what exactly you are trying to accomplish?
Why is the client going through the BIG-IP to talk with a domain controller? Why is the request then going to the internal VLAN when the original request came into the BIG-IP over the external VLAN? What traffic are you trying to load balance? What is the full path the traffic is taking and what objects on the BIG-IP do you want the traffic to go through (VIPs, SNAT's, etc)?
Aaron
Nimbostratus
