A method is provided in one example embodiment and includes invoking a mobile access gateway function based on an end user requesting an Internet Protocol (IP) address in a wireless or a wireline network. The invocation is selective such that the mobile access gateway function is invoked if the end user requires IP mobility services. The method also includes communicating with a gateway in order to obtain the IP address. The mobile access gateway function is coupled to a network element that receives packets for a communications flow from the end user that can conduct the flow through the wireless network and through the wireline network.