6
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 is not 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:
"Glop" is a mechanism for assigning multicast addresses between different 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 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.
224.0.0.14 RSVP
encapsulation.
224.0.0.15 CBT
routers.
224.0.0.16 Designated
SBM.
224.0.0.17 All
SBMs.
224.0.0.18 Virtual
Router
Redundancy Protocol (VRRP).