Consider the case when a mobile node moves from one CZ to another. Once it receives an AP Beacon from the new IN, the MN sends a registration request to the new IN (its FA)3.2. This registration request contains the MN's HA3.3. The FA then sends a Home Agent Registration Request to the MN's HA, thereby informing it of the current location of the MN. On the receipt of a Home Agent Registration Acknowledgement, the FA sends a registration acknowledgement to the MN (Figure 3.1. One must however remember to periodically refresh the MN timeout value at the HA. This is achieved by sending an intimation to the HA on the receipt of an NU packet from a foreign MN.
All packets that are destined to the MN reach its HA, which tunnels those packets to the MN's FA, which in turn routes the packets to the MN using the routing protocol for CZ.