IPv4 Internetwork control block multicast addresses

The Class D multicast addresses in the range of 224.0.1.0/8 (224.0.1.0 through 224.0.1.255) is the Internetwork control block multicast addresses. Internetwork control block addresses are similar to the link-local multicast addresses except that they are forwarded by routers. Internetwork control block addresses is used for traffic that must be routed through the public Internet. For example; Network Time Protocol (NTP) uses 224.0.1.1.

Class D multicast addresses in the range 224.0.1.0 to 224.0.1.255 are individually assigned by ICANN/IANA. Internetwork control block multicast addresses are used by different network infrastructure protocols for protocol communication. For example; Cisco Auto-RP (Rendezvous Point) uses Internetwork control block addresses 224.0.1.39 (cisco-rp-announce) and 224.0.1.40 (cisco-rp-discovery).