Neighbor Solicitation and Advertisement Messages

Neighbor solicitation and advertisement messages enable a node to determine the link-layer address of another node (neighbor) on the same link. (This function is similar to the function provided by the Address Resolution Protocol [ARP] in IPv4.) For example, node 1 on a link wants to determine the link-layer address of node 2 on the same link. To do so, node 1, the source node, multicasts a neighbor solicitation message. The neighbor solicitation message, which has a value of 135 in the Type field of the ICMP packet header, contains the following information:

  • Source address: IPv6 address of node 1 interface that sends the message.
  • Destination address: Solicited-node multicast address (FF02:0:0:0:0:1:FF00::/104) that corresponds to the IPv6 address of node 2.
  • Link-layer address of node 1.
  • A query for the link-layer address of node 2.

After receiving the neighbor solicitation message from node 1, node 2 replies by sending a neighbor advertisement message, which has a value of 136 in the Type field of the ICMP packet header. The neighbor solicitation message contains the following information:

  • Source address: IPv6 address of the node 2 interface that sends the message.
  • Destination address: IPv6 address of node 1.
  • Link-layer address of node 2.

After node 1 receives the neighbor advertisement message from node 2, nodes 1 and 2 can now exchange packets on the link.

After the link-layer address of node 2 is determined, node 1 can send neighbor solicitation messages to node 2 to verify that it is reachable. Also, nodes 1, 2, or any other node on the same link can send a neighbor advertisement message to the all-nodes multicast address (FF02::1) if there is a change in their link-layer address.

Parent topic: IPv6 Neighbor Discovery Configuration