Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 Multicast Overview
1-7
hosts, and the TCP/IP stack must support reception and transmission of multicast
data.
1.3.1 Multicast Addresses
To allow communication between multicast sources and multicast group members,
network-layer multicast addresses, namely, multicast IP addresses must be provided.
In addition, a technique must be available to map multicast IP addresses to link-layer
multicast MAC addresses.
I. IPv4 multicast addresses
Internet Assigned Numbers Authority (IANA) assigned the Class D address space
(224.0.0.0 to 239.255.255.255) for IPv4 multicast. The specific address blocks and
usages are shown in
Table 1-2
Class D IP address blocks and description
Address block
Description
224.0.0.0 to
224.0.0.255
Reserved permanent group addresses. The IP address
224.0.0.0 is reserved, and other IP addresses can be used
by routing protocols and for topology searching, protocol
maintenance, and so on. Commonly used permanent group
addresses are listed in
. A packet destined for an
address in this block will not be forwarded beyond the local
subnet regardless of the Time to Live (TTL) value in the IP
header.
224.0.1.0 to
238.255.255.255
Globally scoped group addresses. This block includes two
types of designated group addresses:
z
232.0.0.0/8: SSM group addresses, and
z
233.0.0.0/8: Glop group addresses; for details, see RFC
2770.
239.0.0.0 to
239.255.255.255
Administratively scoped multicast addresses. These
addresses are considered to be locally rather than globally
unique, and can be reused in domains administered by
different organizations without causing conflicts. For details,
refer to RFC 2365.
Note:
z
The membership of a group is dynamic. Hosts can join or leave multicast groups at
any time.
z
“Glop” is a mechanism for assigning multicast addresses between different
autonomous systems (ASs). By filling an AS number into the middle two bytes of
233.0.0.0, you get 255 multicast addresses for that AS.
