
6
IP multicast addresses
1.
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.
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, protocol maintenance, and so
on.
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 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 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, and can
be reused in domains administered by different organizations
without causing conflicts. For more information, see RFC 2365.
NOTE:
•
The membership of a group is dynamic. Hosts can join or leave multicast groups at any time.
•
"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. 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
Distance Vector Multicast Routing Protocol (DVMRP) routers
224.0.0.5
Open Shortest Path First (OSPF) routers
224.0.0.6
OSPF designated routers/backup designated routers
224.0.0.7
Shared Tree (ST) routers
224.0.0.8 ST
hosts
224.0.0.9
Routing Information Protocol version 2 (RIPv2) routers
224.0.0.11 Mobile
agents
224.0.0.12
Dynamic Host Configuration Protocol (DHCP) server/relay agent
224.0.0.13
All Protocol Independent Multicast (PIM) routers
224.0.0.14 Resource
Reservation Protocol (RSVP) encapsulation
224.0.0.15
All Core-Based Tree (CBT) routers