IPv6

Neighbour discovery

Also called NDP, neighbor solicitation, neighbor advertisement, solicited-node multicast, ICMPv6

IPv6's replacement for ARP, and more: ICMPv6 messages to find neighbours and routers.

A neighbour solicitation asks for an address's MAC, sent to its solicited-node multicast group (ff02::1:ff + its last 24 bits) instead of a broadcast; the advertisement answers. The same machinery checks an address is unused before taking it (duplicate address detection) and carries router solicitations and advertisements. It is all ICMPv6, so a firewall that drops ICMPv6 breaks IPv6 itself: filter it by type.

See it on real machines

Learn it on real machines.