Solicited-node multicast address

A Solicited-Node multicast address is an IPv6 multicast address used by the Neighbor Discovery Protocol to determine the link layer address associated with a given IPv6 address, which is also used to check if an address is already being used by the local-link or not, through a process called DAD (Duplicate Address Detection). 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.

A Solicited-Node address is created by taking the least-significant 24 bits of a unicast or anycast address and appending them to the prefix ff02::1:ff00:0/104.[1]

Example

Assume a host with a unicast/anycast IPv6 address of fe80::2aa:ff:fe28:9c5a. Its Solicited-Node multicast address will be ff02::1:ff28:9c5a.

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
  1. R. Hinden; S. Deering (February 2006). IP Version 6 Addressing Architecture. Network Working Group. doi:10.17487/RFC4291. RFC 4291. Updated by: RFC 5952, RFC 6052, RFC 7136, RFC 7346, RFC 7371, RFC 8064.
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