The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 4 (IP, IPv4)                      9  IP Addressing                           9  IP "Classful" (Conventional) Addressing

IP Reserved, Loopback and Private Addresses 1 2 Problems With "Classful" IP Addressing

Well-Known Multicast Addresses

The first block of 256 addresses is used to define special, well-known multicast address blocks. These do not represent arbitrary groups of devices and cannot be assigned in that manner. Instead, they have special meaning that allows a source to send a message to a predefined group. Table 49 shows some of the “well-known” multicast addresses:

Delivery of IP multicast traffic is more complex than unicast traffic due to the existence of multiple recipients. Instead of the normal resolution method through the ARP protocol used for unicast datagrams, a special mapping is performed between the IP multicast group and a hardware multicast group.

IP Reserved, Loopback and Private Addresses 1 2 Problems With "Classful" IP Addressing