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IGMP Snooping requires that one central switch or router periodically query all end-devices on the network to announce their multicast memberships. This central device is the "IGMP Querier". The IGMP query responses, known as IGMP reports, keep the switch updated with the current multicast group membership on a port-by- port basis. If the switch does not receive updated membership information in a timely fashion, it will stop forwarding multicasts to the port where the end device is located.
This section describes commands used to configure and display information on IGMP Snooping Queriers on the network and, separately, on VLANs.
Use this command to enable IGMP Snooping Querier on the system, using Global Config mode, or on a VLAN. Using this command, you can specify the IP Address that the Snooping Querier switch should use as the source address while generating periodic queries.
If a VLAN has IGMP Snooping Querier enabled and IGMP Snooping is operationally disabled on it, IGMP Snooping Querier functionality is disabled on that VLAN. IGMP Snooping functionality is re-enabled if IGMP Snooping is operational on the VLAN.
Note: The Querier IP Address assigned for a VLAN takes preference over global configuration.
The IGMP Snooping Querier application supports sending periodic general queries on the VLAN to solicit membership reports.
Use this command to disable IGMP Snooping Querier on the system. Use the optional address parameter to reset the querier address to 0.0.0.0.
Use this command to set the IGMP Querier Query Interval time. It is the amount of time in seconds that the switch waits before sending another general query.
Use this command to set the IGMP Querier Query Interval time to its default value.
Use this command to set the IGMP Querier timer expiration period. It is the time period that the switch remains in Non-Querier mode once it has discovered that there is a Multicast Querier in the network.
Use this command to set the IGMP Querier timer expiration period to its default value.
Use this command to set the IGMP version of the query that the snooping switch is going to send periodically.
Use this command to set the IGMP Querier version to its default value.
Use this command to enable the Snooping Querier to participate in the Querier Election process when it discovers the presence of another Querier in the VLAN. When this mode is enabled, if the Snooping Querier finds that the other Querier’s source address is better (less) than the Snooping Querier’s address, it stops sending periodic queries. If the Snooping Querier wins the election, then it will continue sending periodic queries.
Use this command to set the Snooping Querier not to participate in querier election but go into non-querier mode as soon as it discovers the presence of another querier in the same VLAN.
Use this command to display IGMP Snooping Querier information. Configured information is displayedwhether or not IGMP Snooping Querier is enabled.
When the optional argument vlanid is not used, the command displays the following information.
When you specify a value for vlanid, the following additional information appears.
When the optional argument detail is used, the command shows the global information and the information for all Querier-enabled VLANs.