4000 Router Series IP Multicast Configuration Guide

Multicast addresses

IP multicast addresses

• IPv4 multicast addresses:

IANA assigns the Class D address block (224.0.0.0 to 239.255.255.255) to IPv4 multicast.

Table 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. Other IP addresses can be used by routing protocols and

for topology searching, and protocol maintenance. Table 3 lists

common permanent group addresses. A packet destined for an

address in this block will not be forwarded beyond the local subnet

regardless of the TTL value in the IP header.

224.0.1.0 to 238.255.255.255

Globally scoped group addresses. This block includes the following

types of designated group addresses:

• 232.0.0.0/8—SSM group addresses.

• 233.0.0.0/8—Glop group addresses.

239.0.0.0 to 239.255.255.255

Administratively scoped multicast addresses. These addresses are

considered locally unique rather than globally unique. You can

reuse them in domains administered by different organizations

without causing conflicts. For more information, see RFC 2365.

NOTE:

"Glop" is a mechanism for assi

nin

multicast addresses between different ASs. By fillin

an AS numbe

into the middle two bytes of 233.0.0.0, you get 255 multicast addresses for that AS. For more

information, see RFC 2770.

Table 3 Some reserved multicast addresses

Address Description

224.0.0.1 All systems on this subnet, including hosts and routers.

224.0.0.2 All multicast routers on this subnet.

224.0.0.3 Unassigned.

224.0.0.4 DVMRP routers.

224.0.0.5 OSPF routers.

224.0.0.6 OSPF designated routers and backup designated routers.

224.0.0.7 Shared Tree (ST) routers.

224.0.0.8 ST hosts.

224.0.0.9 RIPv2 routers.

224.0.0.11 Mobile agents.

224.0.0.12 DHCP server/relay agent.

224.0.0.13 All Protocol Independent Multicast (PIM) routers.