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Configuring IP Multicast
The IP multicast feature enables a host to send packets to a subset of hosts known as a multicast group.
The hosts in the multicast group are the group members. Packets delivered to group members are
identified by a single multicast group address. Multicast packets are delivered to a group using
best-effort reliability. Any host, regardless of whether it is a member of a group, can send messages to a
group. However, only the members of a group can receive the messages.
Enhancements to the IP multicast feature provide support for broadband environments. This enhanced
IP multicast feature allows PPPoA, PPPoE, and RBE subscribers to participate in multicast groups and
to initiate multicast messages.
The IP multicast feature supports the following protocols to implement IP multicast routing:
•
Internet Group Management Protocol (IGMP)—Used between hosts on a LAN and the router(s) on
that LAN to track the multicast groups of which hosts are members.
•
Protocol-Independent Multicast (PIM)—Used between routers so that they can track which
multicast packets to forward to each other to their directly connected LANs.
•
Distance Vector Multicast Routing Protocol (DVMRP)—Used on the multicast backbone of the
Internet. The Cisco IOS software supports PIM-to-DVMRP interaction. However, you cannot run
DVMRP back-to-back between Cisco routers.
•
Cisco Group Management Protocol (CGMP)—Used on routers connected to Cisco Catalyst
switches to perform tasks similar to those performed by IGMP.
Note
For more information about the IP multicast feature, see the “IP Multicast” chapter in the
Cisco IOS IP Configuration Guide
, Release 12.2.
This chapter describes the IP Multicast feature in the following topics:
•
Feature History for IP Multicast, page 15-34
•
Restrictions for IP Multicast, page 15-34
•
Configuration Tasks for IP Multicast Routing, page 15-34
