Enabling Ip Multicast Routing - Cisco Catalyst 4500 series Administration Manual

Configuring IP Multicast Routing
Table 37-1
Feature
Rate limiting of RPF
IP multicast routing
PIM
IGMP snooping
Source-specific multicast and IGMP v3 are supported.
Note
For more information about source-specific multicast with IGMPv3 and IGMP, see the following URL:
http://www.cisco.com/en/US/docs/ios/ipmulti/configuration/guide/imc_cfg_ssm.html

Enabling IP Multicast Routing

Enabling IP multicast routing allows the Catalyst 4500 series switch to forward multicast packets. To
enable IP multicast routing on the router, enter this command:
Command
Switch(config)# ip multicast-routing
Enabling PIM on an Interface
Enabling PIM on an interface also enables IGMP operation on that interface. An interface can be
configured to be in dense mode, sparse mode, or sparse-dense mode. The 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.
When the switch populates the multicast routing table, dense-mode interfaces are always added to the
table. Sparse-mode interfaces are added to the table only when periodic join messages are received from
downstream routers, or when there is a directly connected member on the interface. When forwarding
from a LAN, sparse-mode operation occurs if there is an RP known for the group. If so, the packets are
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
37-14
Default IP Multicast Configuration
Default Value
Enabled globally
Disabled globally
When IP multicast routing is disabled, IP multicast traffic data
Note
packets are not forwarded by the Catalyst 4500 series switch.
However, IP multicast control traffic continues to be processed and
forwarded. IP multicast routes can remain in the routing table even
if IP multicast routing is disabled.
Disabled on all interfaces
Enabled on all VLAN interfaces
If you disable IGMP snooping on an interface, all output ports are
Note
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 switch ports in the
VLAN.
Chapter 37
Purpose
Enables IP multicast routing.
Configuring IP Multicast
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