To effect seamless transition of a mobile terminal user (16) from a first radio access network (12) to second radio access network (14), a temporary home agent (19) in the second radio access network assigns the user a co-location address which becomes the source address for all packets originated by the user while accessing the second network. Packets sent in reply to those originated with the co-location address as the source address pass directly to the mobile terminal user at the second network without first being tunneled through the first radio access network. Upon the transition of the mobile terminal user to the second radio access network, the first radio access network will forward any packets addressed to the user at the first source address.