Setting The Snooping Method - Cisco Catalyst 2360 Software Configuration Manual

Configuring IGMP Snooping

Setting the Snooping Method

Multicast-capable router ports are added to the forwarding table for every Layer 2 multicast entry. The
switch learns of such ports through one of these methods:
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You can configure the switch either to snoop on IGMP queries and PIM/DVMRP packets or to listen to
CGMP self-join or proxy-join packets. By default, the switch snoops on PIM/DVMRP packets on all
VLANs. To learn of multicast router ports through only CGMP packets, use the ip igmp snooping vlan
vlan-id mrouter learn cgmp global configuration command. When this command is entered, the router
listens to only CGMP self-join and CGMP proxy-join packets and to no other CGMP packets. To learn
of multicast router ports through only PIM-DVMRP packets, use the ip igmp snooping vlan vlan-id
mrouter learn pim-dvmrp global configuration command.
Note If you want to use CGMP as the learning method and no multicast routers in the VLAN are CGMP
proxy-enabled, you must enter the ip cgmp router-only command to dynamically access the router.
Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface
dynamically accesses a multicast router:
Command
Step 1 configure terminal
Step 2 ip igmp snooping vlan vlan-id mrouter
learn {cgmp | pim-dvmrp}
Step 3 end
Step 4 show ip igmp snooping
Step 5
copy running-config startup-config
To return to the default learning method, use the no ip igmp snooping vlan vlan-id mrouter learn cgmp
global configuration command.
This example shows how to configure IGMP snooping to use CGMP packets as the learning method:
Switch# configure terminal
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp
Switch(config)# end
Catalyst 2360 Switch Software Configuration Guide
15-8
Snooping on IGMP queries, Protocol-Independent Multicast (PIM) packets, and Distance Vector
Multicast Routing Protocol (DVMRP) packets
Listening to Cisco Group Management Protocol (CGMP) packets from other routers
Statically connecting to a multicast router port with the ip igmp snooping mrouter global
configuration command
Purpose
Enter global configuration mode.
Enable IGMP snooping on a VLAN. The VLAN ID range is 1 to 1001
and 1006 to 4094.
Specify the multicast router learning method:
cgmp—Listen for CGMP packets. This method is useful for
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reducing control traffic.
pim-dvmrp—Snoop on IGMP queries and PIM-DVMRP packets.
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This is the default.
Return to privileged EXEC mode.
Verify the configuration.
(Optional) Save your entries in the configuration file.
Chapter 15 Configuring IGMP Snooping
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