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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter24 Understanding and Conf iguring IP Multicast
Configuring IP Multicast Routing
Default Configuration in IP MUlticast Routing
Table24-1 shows the IP multicast default configuration.
Note Source-specific multicast and IGMP v3 are supported.
For more information about source-specific multicast with IGMPv3 and IGMP, see the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcpt3/1cfssm.htm
Enabling IP Multicast Routing
Enabling IP multicast routing allows the Catalyst4500 series switch to forward multicast packets. To
enable IP multicast routing on the router, perform this task in global configuration mode:
Enabling PIM on an Interface
Enabling PIM on an interface also enables IGMP oper ation on that interface. An interface can be
configured to be in dense mode, sparse mode, or sparse-dense mode. T he mode determines how the
Layer 3 switch or router populates its multicast routing table and how the Layer 3 switch or router
forwards multicast packets it receives from its directly connected LANs. You must enable PIM in one of
these modes for an interface to perform IP multicast routing.
Table24-1 Default IP Multicast Configuration
Feature Default Value
Rate limiting of RPF Enabled globally
IP multicast routing Disabled globally
Note When IP multicast routing is disabled, IP multicast traffic data
packets are not forwarded by the Catalyst 4500 series switch.
However, IP multicast control traffic will continue to be processed
and forwarded. Therefore, IP multicast routes can remain in the
routing table even if IP multicast routing is disabled.
PIM Disabled on all interfaces
IGMP snooping Enabled on all VLAN interfaces
Note If you disable IGMP snooping on an interface, all output po rts are
forwarded by the Integrated Switching Engine. When IGMP
snooping is disabled on an input VLAN interface, multicast packets
related to that interface are sent to all forwarding switchports in the
VLAN.
Command Purpose
Switch(config)# ip multicast-routing Enables IP multicast routing.