9.1 Multicasting Overview
9.1.3
Layer 3 multicast addressing
IP multicast addresses at Layer 3 are characterized as Class D addresses. The first four bits of IP Class D addresses are 1110. This means that IP multicast addresses have a valid range from 224.0.0.0 to 239.255.255.255. Note that multicast addresses from 224.0.0.0 to 224.0.0.255 are reserved. The reserved addresses shown in the Figure are specifically relevant to multicasting.

Usually, a network administrator assigns a multicast address to the application and must select an address not used by other applications or processes. The administrator should not use a multicast address in the reserved range.