Cisco Systems EA6500 Manual De Usuario

Periodically, the IGMP querier sends IGMP queries that trigger IGMP report messages from the 
switch that wants to receive IP multicast traffic.

IGMP snooping listens to these IGMP reports to establish appropriate forwarding. In a normal 
network with IP multicast routing, the IP multicast router acts as the IGMP querier. 

To enable IP multicast routing on the Catalyst 6500 series switches on a specific VLAN, enter 
the ip pim sparse-mode command, the ip pim sparse-dense-mode command, or the ip pim 
dense-mode command on that interface. See 

 for more details.

If the IP-multicast traffic in a VLAN needs to be Layer 2 switched only, an IP-multicast router is 
not required, but without an IP-multicast router on a VLAN, you must configure another switch as 
the IGMP querier so that it can send queries. You can use Cisco IOS commands to configure the 
Catalyst 6500 series switches to generate such IGMP queries on a VLAN regardless of whether or 
not IP multicast routing is enabled.

IGMP snooping querier requires Release 12.1(8a)E and later. 

When configuring the IGMP snooping querier, configure the VLAN in the VLAN database or, with 
Release 12.1(11b)E and later releases, configure the VLAN in global configuration mode (see 

).

QoS does not support IGMP packets when IGMP snooping is enabled.

You must configure an IP address on the VLAN interface for the IGMP snooping querier to start. 
(See 

). When enabled, the IGMP snooping querier uses 

the IP address as the query source address. The IGMP snooping querier disables itself if the IP 
address is cleared and restarts when you configure an IP address. 

With Release 12.1(11b)E and later, when you are in configuration mode you can enter EXEC mode-level 
commands by entering the do keyword before the EXEC mode-level command.

With Release 12.1(8a)E and later, use the IGMP snooping querier to support IGMP snooping in a VLAN 
where PIM and IGMP are not configured because the multicast traffic does not need to be routed.

To enable the IGMP snooping querier in a VLAN, perform this task:

Router(config)# interface vlan vlan_ID 

Selects the VLAN interface.

Router(config-if)# ip igmp snooping querier 

Enables the IGMP snooping querier. 

Router(config-if)# no ip igmp snooping querier 

Disables the IGMP snooping querier.