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z The membership of a group is dynamic. A host can join and leave a multicast group at any time.
z A multicast group can be either permanent or temporary.
z A multicast group whose addresses are assigned by IANA is a permanent multicast group. It is also
called reserved multicast group.
Note that:
z The IP addresses of a permanent multicast group keep unchanged, while the members of the
group can be changed.
z There can be any number of, or even zero, members in a permanent multicast group.
z Those IP multicast addresses not assigned to permanent multicast groups can be used by
temporary multicast groups.
Class D IP addresses range from 224.0.0.0 to 239.255.255.255. For details, see
Table 1-2.
Table 1-2 Range and description of Class D IP addresses
Class D address range Description
224.0.0.0 to 224.0.0.255
Reserved multicast addresses (IP addresses for
permanent multicast groups). The IP address
224.0.0.0 is reserved. Other IP addresses can
be used by routing protocols.
224.0.1.0 to 231.255.255.255
233.0.0.0 to 238.255.255.255
Available any-source multicast (ASM) multicast
addresses (IP addresses for temporary groups).
They are valid for the entire network.
232.0.0.0 to 232.255.255.255
Available source-specific multicast (SSM)
multicast group addresses.
239.0.0.0 to 239.255.255.255
Administratively scoped multicast addresses,
which are for specific local use only.
As specified by IANA, the IP addresses ranging from 224.0.0.0 to 224.0.0.255 are reserved for network
protocols on local networks. The following table lists commonly used reserved IP multicast addresses:
Table 1-3 Reserved IP multicast addresses
Class D address range Description
224.0.0.1 Address of all hosts
224.0.0.2 Address of all multicast routers
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
Open Shortest Path First designated routers
(OSPF DR)
224.0.0.7 Shared tree routers
224.0.0.8 Shared tree hosts
224.0.0.9 RIP-2 routers
224.0.0.11 Mobile agents
224.0.0.12 DHCP server/relay agent