IPv6 - Solicited Node Multicast Address

IPv6 uses the neighbor solicitation (NS) message primarily to find the layer two address of another IPv6 address on the local link. It is the counterpart to IPv4's ARP.

The destination address of an NS message will be the solicited-node multicast address of the remote host. Using solicited-node multicast addresses as the destination is far more efficient than ARP requests broadcast to all hosts.

Every IPv6 device will compute a solicited-node multicast address by taking the multicast group address FF02::1:FF /104 and adding the last six hexadecimal characters from its IPv6 address. It will then join this multicast group address and “listens” to it.

When one host wants to find the layer two address of another host, it will send the neighbor solicitation to the remote host’s solicited node multicast address. It can calculate the solicited-node multicast address of the remote host since it knows about the multicast group address and it knows the IPv6 address that it wants to reach.

The result will be that only the remote host will receive the neighbor solicitation. That’s far more efficient than a broadcast that everyone receives.