Techniques are described for performing inline NAT functions in a forwarding element of a mobile gateway router or other device in which subscriber sessions of a mobile access network are distributed across a plurality of session management cards. The session management cards pre-allocate a public network address and port range for subscribers at the time a network connection is established in response to connection request prior to receiving any data traffic associated with the subscriber. NAT profiles are programmed into hardware forwarding elements of the mobile gateway router for inline NAT when routing subscriber traffic for the mobile access network.