Chapter 24 Configuring Ip Multicast Routing - Cisco WS-C3550-12G Software Configuration Manual

Configuring IP Multicast Routing
IP multicasting is a more efficient way to use network resources, especially for bandwidth-intensive
services such as audio and video. IP multicast allows a host (source) to send packets to a group of hosts
(receivers) anywhere within the IP network by using a special form of IP address called the IP multicast
group address. The sending host inserts the multicast group address into the IP destination address field
of the packet, and IP multicast routers and multilayer switches forward incoming IP multicast packets
out all interfaces that lead to members of the multicast group.
IP multicast addresses are assigned to the old class D address space by the Internet Assigned Number
Authority (IANA). The high-order bits of a Class D address are 1110. Therefore, host group addresses
can be in the range 224.0.0.0 through 239.255.255.255. The address 224.0.0.0 is guaranteed not to be
assigned to any group. The address 224.0.0.1 is assigned to the all-hosts multicast group on a subnet.
The address 224.0.0.2 is assigned to the all-multicast-routers group on a subnet.
Any host, regardless of whether it is a member of a group, can send to a group. However, only the
members of a group receive the message. Membership in a multicast group is dynamic; hosts can join
and leave at any time. There is no restriction on the location or number of members in a multicast group.
A host can be a member of more than one multicast group at a time. How active a multicast group is and
what members it has can vary from group to group and from time to time. A multicast group can be active
for a long time, or it can be very short-lived. Membership in a group can constantly change. A group that
has members can have no activity.
Note For complete syntax and usage information for the commands used in this chapter, refer to the Cisco
IOS IP and IP Routing Command Reference for Release 12.1.
This chapter describes how to configure IP multicast routing on your multilayer switch. To use this
feature, you must have the enhanced multilayer software image (EMI) installed on your switch. All
Catalyst 3550 Gigabit Ethernet switches ship with the EMI installed. Catalyst 3550 Fast Ethernet
switches can be shipped with either the standard multilayer software image (SMI) or EMI pre-installed.
You can order the Enhanced Multilayer Software Image Upgrade kit to upgrade Catalyst 3550 Fast
Ethernet switches from the SMI to the EMI.
This chapter consists of these sections:
Cisco Implementation of IP Multicast Routing, page 24-2
•
Configuring IP Multicast Routing, page 24-13
•
• Configuring Advanced PIM Features, page 24-28
• Configuring Optional IGMP Features, page 24-31
Configuring Optional Multicast Routing Features, page 24-37
•
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