Page "Open Shortest Path First" Paragraph 9

OSPF uses multicast addressing for route flooding on a broadcast network link.

For non-broadcast networks special provisions for configuration facilitate neighbor discovery.

OSPF multicast IP packets never traverse IP routers, they never travel more than one hop.

OSPF reserves the multicast addresses < tt > 224. 0. 0. 5 </ tt > for IPv4 or < tt > FF02 :: 5 </ tt > for IPv6 ( all SPF / link state routers, also known as < tt > AllSPFRouters </ tt >) and < tt > 224. 0. 0. 6 </ tt > for IPv4 or < tt > FF02 :: 6 </ tt > for IPv6 ( all Designated Routers, < tt > AllDRouters </ tt >), as specified in RFC 2328 and RFC 5340.