A system and method are provided for mobile Internet Protocol (IP) addressing, in a multi-mode wireless communications access terminal (AT). The method provides an AT with an IP address (ATA), and a care-of-address (CoA) in each of a plurality of networks. In one aspect, the AT selects a first network for transmission, from the plurality of networks. The AT sends an IP packet to a correspondent node (CN) via a first mobile node (MN) external device. Regardless of the network selected, the AT is able to use the ATA as a source address. Sending the IP packet to the CN may include creating a tunnel between the first MN and the HA. The IP packet is sent to the HA using the first CoA as a tunnel source address, and the HA sends the IP packet to the CN using the ATA as the source address.