Comnet CWGE24MS2 Installation And Operation Manual page 89

INSTALLATION AND OPERATION MANUAL
Multicast Address
Introduction
A multicast address is associated with a group of interested receivers. According to RFC 3171,
addresses 224.0.0.0 to 239.255.255.255, the former Class D addresses, are designated as multicast
addresses in IPv4.
The IANA owns the OUI MAC address 01:00:5e, therefore multicast packets are delivered by using
the Ethernet MAC address range 01:00:5e:00:00:00 - 01:00:5e:7f:ff:ff. This is 23 bits of available
address space.
The first octet (01) includes the broadcast/multicast bit. The lower 23 bits of the 28-bit multicast
IP address are mapped into the 23 bits of available Ethernet address space. This means that there
is ambiguity in delivering packets. If two hosts on the same subnet each subscribe to a different
multicast group whose address differs only in the first 5 bits, Ethernet packets for both multicast
groups will be delivered to both hosts, requiring the network software in the hosts to discard the
unrequired packets.
Class Address Range
Class A 1.0.0.1 to 126.255.255.254
Class B 128.1.0.1 to 191.255.255.254
Class C 192.0.1.1 to 223.255.254.254
Class D 224.0.0.0 to 239.255.255.255
Class E 240.0.0.0 to 254.255.255.254
TECH SUPPORT: 1.888.678.9427
Supports
Supports 16 million hosts on each of 127 networks.
Supports 65,000 hosts on each of 16,000 networks.
Supports 254 hosts on each of 2 million networks.
Reserved for multicast groups.
Reserved for future use, or Research and
Development Purposes.
CWGE24MS2
INS_CWGE24MS2_REV–
10/05/16 PAGE 89