Cisco Systems 3750E Changing the Igmp Version, Modifying the Igmp Host-Query Message Interval

Chapter 42 Configuring IP Multicast Routing

Configuring Optional IGMP Features

	Command	Purpose
Step 7
	show ip igmp interface [interface-id]	Verify your entries.
Step 8
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To disable groups on an interface, use the no ip igmp access-groupinterface configuration command.

This example shows how to configure hosts attached to a port as able to join only group 255.2.2.2:

Switch(config)# access-list 1 255.2.2.2 0.0.0.0

Switch(config-if)#interface gigabitethernet1/0/1

Switch(config-if)#ip igmp access-group 1

Changing the IGMP Version

By default, the switch uses IGMP Version 2, which provides features such as the IGMP query timeout and the maximum query response time.

All systems on the subnet must support the same version. The switch does not automatically detect Version 1 systems and switch to Version 1. You can mix Version 1 and Version 2 hosts on the subnet because Version 2 routers or switches always work correctly with IGMPv1 hosts.

Configure the switch for Version 1 if your hosts do not support Version 2.

Beginning in privileged EXEC mode, follow these steps to change the IGMP version. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify the interface to be configured, and enter interface
		configuration mode.
Step 3
	ip igmp version {1 2}	Specify the IGMP version that the switch uses.
		Note If you change to Version 1, you cannot configure the ip igmp
		query-interval or the ip igmp query-max-response-time
		interface configuration commands.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show ip igmp interface [interface-id]	Verify your entries.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To return to the default setting, use the no ip igmp version interface configuration command.

Modifying the IGMP Host-Query Message Interval

The switch periodically sends IGMP host-query messages to discover which multicast groups are present on attached networks. These messages are sent to the all-hosts multicast group (224.0.0.1) with a time-to-live (TTL) of 1. The switch sends host-query messages to refresh its knowledge of memberships present on the network. If, after some number of queries, the software discovers that no local hosts are members of a multicast group, the software stops forwarding multicast packets to the local network from remote origins for that group and sends a prune message upstream toward the source.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		42-31