Methods and apparatus for supporting broadcast traffic in Mobile IP are disclosed. When a Mobile Node registers via a Foreign Agent supporting Mobile IP, the Foreign Agent receives a registration request from a Mobile Node and sends the registration request to a Home Agent. A registration reply received from the Home Agent has a network mask extension including a network mask associated with the home address of the Mobile Node. The Foreign Agent then sends the registration reply to the Mobile Node. Alternatively, the Mobile Node may register via a collocated care-of address, in which case the registration reply is received directly from the Home Agent. Once the Mobile Node has obtained its network mask, it may send packets such as broadcast packets, as well as roam to its Home Agent. Additionally, in accordance with various embodiments, the Foreign Agent duplicates broadcast packets for transmission to Mobile Nodes, rather than receiving the duplicated packets from the Home Agent. In this manner, broadcast traffic in a Mobile IP environment is optimized.