Setting The Snooping Method - Cisco Catalyst 2950 Software Configuration Manual

Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the
switch:
Command
Step 1
configure terminal
Step 2
ip igmp snooping
Step 3
end
Step 4 show ip igmp snooping
Step 5
copy running-config startup-config
To globally disable IGMP snooping on all VLAN interfaces, use the no ip igmp snooping global
configuration command.
Beginning in privileged EXEC mode, follow these steps to enable IGMP snooping on a VLAN interface:
Command
Step 1 configure terminal
Step 2 ip igmp snooping vlan vlan-id
Step 3
end
Step 4
show ip igmp snooping [vlan vlan-id] Display snooping configuration.
Step 5 copy running-config startup-config
To disable IGMP snooping on a VLAN interface, use the no ip igmp snooping vlan vlan-id global
configuration command for the specified VLAN number (for example, vlan1).

Setting the Snooping Method

Multicast-capable router ports are added to the forwarding table for every IP multicast entry. The switch
learns of such ports through one of these methods:
•
•
•
You can configure the switch to either snoop on PIM/DVMRP packets or to listen to CGMP self-join
packets. By default, the switch snoops on PIM/DVMRP packets on all VLANs. To learn of multicast
router ports through only CGMP self-join packets, use the ip igmp snooping vlan vlan-id mrouter
learn cgmp global configuration command. When this command is used, the router listens only to
CGMP self-join packets and 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.
Catalyst 2950 Desktop Switch Software Configuration Guide
16-6
Purpose
Enter global configuration mode.
Globally enable IGMP snooping in all existing VLAN interfaces.
Return to privileged EXEC mode.
Display snooping configuration.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
Enable IGMP snooping on the VLAN interface.
Return to privileged EXEC mode.
(Optional) vlan-id is the number of the VLAN.
(Optional) Save your entries in the configuration file.
Snooping on Protocol Independent Multicast (PIM) packets and Distance Vector Multicast Routing
Protocol (DVMRP) packets
Listening to Cisco Group Management Protocol (CGMP) self-join packets from other routers
Statically connecting to a multicast router port with the ip igmp snooping mrouter global
configuration command
Chapter 16 Configuring IGMP Snooping and MVR
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