A method and apparatus for dynamic home address assignment by a home agent in multiple network interworking. The invention provides a method and apparatus send a key authorization request from a mobile station to a network device, the request indicating that the mobile station wishes to use a foreign agent care-of address to continue to receive data. The network device assigns a temporary address to the mobile station and creates a security policy database for the mobile station. The mobile station receives agent advertisements from foreign agents that may be able to provide service. The mobile station registers with a foreign agent. The network device then modifies the security policy database to reflect the information of the foreign agent. The Home Agent then assigns a home address to the mobile station and the network device updates the security policy database to include only the mobile device's home address as a selector.