Multicast Addresses - HP 6125G Configuration Manual

Multicast addresses

Network-layer multicast addresses (multicast IP addresses) enables communication between multicast
sources and multicast group members. In addition, a technique must be available to map multicast IP
addresses to link-layer multicast MAC addresses.
IP multicast addresses
IPv4 multicast addresses
•
Internet Assigned Numbers Authority (IANA) assigned the Class D address space (224.0.0.0 to
239.255.255.255) to IPv4 multicast.
Table 2 Class D IP address blocks and description
Address block
224.0.0.0 to 224.0.0.255
224.0.1.0 to 238.255.255.255
239.0.0.0 to 239.255.255.255
NOTE:
"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
224.0.0.1
224.0.0.2
224.0.0.3
224.0.0.4
224.0.0.5
224.0.0.6
224.0.0.7
224.0.0.8
224.0.0.9
224.0.0.11
Description
All systems on this subnet, including hosts and routers
All multicast routers on this subnet
Unassigned
Distance Vector Multicast Routing Protocol (DVMRP) routers
Open Shortest Path First (OSPF) routers
OSPF designated routers and backup designated routers
Shared Tree (ST) routers
ST hosts
Routing Information Protocol version 2 (RIPv2) routers
Mobile agents
Description
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.
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.
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.
6
Table 3