Grouping multicast addresses

Grouping multicast addresses

Shows the space of the whole IP multicast address.

Where:

The 224.0.0.0 to 224.0.0.255 address range is reserved by IANA, and the address 224.0.0.0 is retained without allocation. Other addresses are used by routing protocols and topology search and maintenance protocols. The addresses in this range belong to the local category and will not be forwarded by the router regardless of the TTL value;

The address range from 224.0.1.0 to 238.00000000255 is used as the multicast address of the user group, which is valid for the whole network. 233/8 is the glop address. Glop is a multicast address allocation mechanism between autonomous systems. It directly fills the as number in the middle two bytes of the multicast address. Each autonomous system can obtain 255 multicast addresses;

The range of 239.0.0.0 to 239.255.255.255 addresses is the administratively scoped ses SSEs address of the Local Management Group, which is valid only for a specific local range.

When the IP layer receives the multicast datagram, it searches for the multicast forwarding table based on the target multicast address and forwards the packets.