A ''Solicited-Node multicast address'' is an

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. I ...

multicast address A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link laye ...

used by the

Neighbor Discovery Protocol The Neighbor Discovery Protocol (NDP), or simply Neighbor Discovery (ND), is a protocol of the Internet protocol suite used with Internet Protocol Version 6 (IPv6). It operates at the link layer of the Internet model, and is responsible for g ...

to verify whether a given IPv6 address is already used by the local-link or not, through a process called DAD (Duplicate Address Detection). This allows NDP to assign IPv6 addresses to hosts using SLAAC (IPv6 Stateless Address Autoconfiguration) without the risk of assigning addresses already in use. The Solicited-Node multicast addresses are generated from the host's IPv6 unicast or anycast address, and each interface must have a Solicited-Node multicast address associated with it. NDP sends out a Neighbor Solicitation message (ICMPv6 Type 135) to the Solicited-Node multicast address of the IPv6 unicast or anycast address it plans to assign using SLAAC, and if a host is present in that group, it will respond with a Neighbor Advertisement message (ICMPv6 Type 136), and NDP will know that the IPv6 unicast or anycast address it is trying to assign is already in use. A Solicited-Node address is created by taking the least-significant 24 bits of a

unicast Unicast is data transmission from a single sender (red) to a single receiver (green). Other devices on the network (yellow) do not participate in the communication. In computer networking, unicast is a one-to-one transmission from one point in ...

anycast Anycast is a network addressing and routing methodology in which a single destination IP address is shared by devices (generally servers) in multiple locations. Routers direct packets addressed to this destination to the location nearest the sen ...

address and appending them to the prefix . Updated by: RFC 5952, RFC 6052, RFC 7136, RFC 7346, RFC 7371, RFC 8064.

Example

Assume a host with a unicast/anycast IPv6 address of . Its Solicited-Node multicast address will be .

fe80::2aa:ff:fe28:9c5a                      IPv6 unicast/anycast address (compressed notation)
fe80:0000:0000:0000:02aa:00ff:fe28:9c5a     IPv6 unicast/anycast address (uncompressed notation)
                                -- ----     the least-significant 24-bits
ff02::1:ff00:0/104                          Solicited-Node multicast address prefix
ff02:0000:0000:0000:0000:0001:ff00:0000/104 (uncompressed)
---- ---- ---- ---- ---- ---- --            The first 104 bits
ff02:0000:0000:0000:0000:0001:ff28:9c5a     Solicited-Node multicast address (uncompressed notation)
ff02::1:ff28:9c5a                           Solicited-Node multicast address (compressed notation)

References

{{Reflist IPv6 Network addressing