Since packets destined for a Mobile Node may be incorrectly routed to its home network, placing Home Agents within an IPv6 edge router would allow the efficient interception of these packets, as they would likely travel through that router. However, the assumption that the packets will automatically reach this edge router cannot be relied upon. For example, consider the case of a Correspondent Node located on a Mobile Node’s home network. If the Correspondent Node were to send a packet to that Mobile Node, its routing table would dictate that the Mobile Node was directly accessible, and did not require forwarding by a router. In this case, the Home Agent would not be able to intercept the packet.

Mobile IPv6 addresses this issue through a technique call proxy neighbour discovery (proxy ND). Neighbour Discovery [RFC2461] is a standard IPv6 protocol for the discovery of MAC addresses from IPv6 addresses, similar in concept to the ARP protocol for IPv4. Proxy ND involves an IPv6 node masquerading as another node at the MAC layer, by falsely responding to neighbour solicitations with its own MAC address. Home agents use proxy ND to ensure they intercept any IPv6 packets for a Mobile Node transmitted on its home network. To accomplish this, Home Agents also maintain a proxy neighbour discovery table, which contains the IPv6 addresses to which the Home Agent is acting as a proxy for. Entries to this table are added and removed as binding update messages with the‘Home Agent’ flag set are added and removed from the binding cache.