The relationship between a Mobile Node's home address and its current care-of address is known as a binding. All Nodes participating in MIPv6 are required to maintain a table of these bindings in a binding cache. One entry is held in the binding cache for each Mobile Node with which communication is currently taking place. The binding cache holds four pieces of information per binding which are central to the operation of MIPv6, as illustrated by Table 10-1 (other fields are present to ensure correct ordering of control messages, but these are omitted for clarity). The home address forms the key field of the cache.

When a node wishes to transmit an IPv6 packet to a remote host, the home address field of the binding cache is searched for the IPv6 address of that host. If no match is found, the packet is transmitted according to the normal IPv6 routing tables. However, if a match is found, then the packet is encapsulated prior to transmission, to redirect the packet to the care-of address specified in the binding cache. This ensures optimal routing to the Mobile Node’s current location. The form this encapsulation takes is dependant on the state of the Home Agent flag stored in the binding cache entry.