When a host is connected to a link or network, it acquires an IP address and all communication take place using that IP address on that link. As soon as, the same host changes its physical location, that is, moves into another area / subnet / network / link, its IP address changes accordingly, and all the communication taking place on the host using old IP address, goes down.

IPv6 mobility provides a mechanism for the host to roam around different links without losing any communication/connection and its IP address.

Care-of Address: When a Mobile Node gets attached to a Foreign Link, it acquires a new IP address of that Foreign Link’s subnet. Home Agent maintains the information of both Home Address and Care-of Address. Multiple Care-of addresses can be assigned to a Mobile Node, but at any instance, only one Care-of Address has binding with the Home Address.