In fact, IPv4 and IPv6 both have a reserved range of multicast addresses (formerly called "Class D"): https://en.wikipedia.org/wiki/Multicast_address https://e

In fact, IPv4 and IPv6 both have a reserved range of multicast addresses (formerly called "Class D"): https://en.wikipedia.org/wiki/Multicast_address https://en.wikipedia.org/wiki/Multicast_address There were more than a few people who spotted how disused this range had become after mbone experiments, and sometimes suggested reclaiming the range as IPv4 address space was being exhausted. Interestingly, there are reserved multicast addresses (yes, addresses, not ports) not only for OSPF, but for many other interior routing protocols, as well as mDNS, LLMNR, and NTP. Conspicuously absent is any reservation for BGP.