1. Install NIC and give it an IP address on a different network than the production interface. Point your DNS at this name
2. Make sure your master server has an acceptable route to this network - the master *MUST* be able to talk to the client
3. Make sure the media server has an acceptable route to the client's new name
2. Update your NBU policy to use this new name
It really is as simple as that. You don't need to use the required interface stuff at all. Let the network stacks do the routing.
.../Ed