The term "IP mobility" describes the ability of a host that is able to move its network connection from one point on the Internet to another without changing its IP address or losing connectivity. Usually when an IP host changes its point of connectivity it must also change its IP address. IP Mobility overcomes this problem by allocating a fixed IP address to the mobile host and using IP encapsulation (tunneling) with automatic routing to ensure that datagrams destined for it are routed to the actual IP address it is currently using.
A project is underway to provide a complete set of IP mobility tools for Linux. The Status of the project and tools may be obtained from the: Linux Mobile IP Home Page.