This output shows a querier for VLAN 1 and 401 with their queries reaching the switch through
GigabitEthernet1/0/11:
Switch# show ip igmp snooping querier
Vlan IP Address IGMP Version Port
-------------------------------------------------------------
1 1.1.1.1 v2 Gi1/0/11
401 41.41.41.1 v2 Gi1/0/11
This is output for the show ip igmp snooping mrouter command for VLAN 1 and 401:
Switch# show ip igmp snooping mrouter
Vlan ports
---- -----
1 Gi1/0/11(dynamic), Gi1/0/12(dynamic)
401 Gi1/0/11(dynamic), Gi1/0/12(dynamic)
Similarly, both the Flex Links ports are a part of the learned groups. In this example, GigabitEthernet2/0/11
is a receiver/host in VLAN 1, which is interested in two multicast groups:
Switch# show ip igmp snooping groups
Vlan Group Type Version Port List
-----------------------------------------------------------------------
1 228.1.5.1 igmp v2 Gi1/0/11, Gi1/0/12, Gi2/0/11
1 228.1.5.2 igmp v2 Gi1/0/11, Gi1/0/12, Gi2/0/11
Whenever a host responds to the general query, the switch forwards this report on all the mrouter ports. When
you turn on this feature through the command-line port, and when a report is forwarded by the switch on
GigabitEthernet1/0/11, it is also leaked to the backup port GigabitEthernet1/0/12. The upstream router learns
the groups and starts forwarding multicast data, which is dropped at the ingress because GigabitEthernet1/0/12
is blocked. When the active link, GigabitEthernet1/0/11, goes down, the backup port, GigabitEthernet1/0/12,
begins forwarding. You do not need to send any proxy reports as the multicast data is already being forwarded
by the upstream router. By leaking reports to the backup port, a redundant multicast path has been set up, and
the time taken for the multicast traffic convergence is very minimal.
Related Topics
Multicast Fast Convergence with Flex Links Failover, on page 150
Additional References for Flex Links and MAC Address-Table
Move Update
Related Documents
Document TitleRelated Topic
Catalyst 2960-XR Switch Layer 2 Command Reference
Layer 2 command reference
Catalyst 2960-XR Switch Interface and Hardware Component
Command Reference
switchport backup interface command
Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1
OL-29424-01 165
Configuring Flex Links and the MAC Address-Table Move Update Feature
Additional References for Flex Links and MAC Address-Table Move Update
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