Cisco Catalyst 2975 Software Configuration Manual page 501

Chapter 19 Configuring Flex Links and the MAC Address-Table Move Update Feature
This output shows a querier for VLANs 1 and 401, with their queries reaching the switch through Gigabit
Ethernet1/0/11:
Switch# show ip igmp snooping querier
Vlan
-------------------------------------------------------------
1
401
Here is output for the show ip igmp snooping mrouter command for VLANs 1 and 401:
Switch# show ip igmp snooping mrouter
Vlan
----
1
401
Similarly, both Flex Link ports are part of learned groups. In this example, Gigabit Ethernet2/0/11 is a
receiver/host in VLAN 1, which is interested in two multicast groups:
Switch# show ip igmp snooping groups
Vlan
-----------------------------------------------------------------------
1
1
When a host responds to the general query, the switch forwards this report on all the mrouter ports. In
this example, when a host sends a report for the group 228.1.5.1, it is forwarded only on Gigabit
Ethernet1/0/11, because the backup port Gigabit Ethernet1/0/12 is blocked. When the active link,
Gigabit Ethernet1/0/11, goes down, the backup port, Gigabit Ethernet1/0/12, begins forwarding.
As soon as this port starts forwarding, the switch sends proxy reports for the groups 228.1.5.1 and
228.1.5.2 on behalf of the host. The upstream router learns the groups and starts forwarding multicast
data. This is the default behavior of Flex Link. This behavior changes when the user configures fast
convergence using the switchport backup interface gigabitEthernet 1/0/12 multicast
fast-convergence command. This example shows turning on this feature:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet 1/0/11
Switch(config-if)# switchport backup interface gigabitethernet 1/0/12 multicast
fast-convergence
Switch(config-if)# exit
Switch# show interfaces switchport backup detail
Switch Backup Interface Pairs:
Active
------------------------------------------------------------------------
GigabitEthernet1/0/11 GigabitEthernet1/0/12 Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : On
Bandwidth : 100000 Kbit (Gi1/0/11), 100000 Kbit (Gi1/0/12)
Mac Address Move Update Vlan : auto
This output shows a querier for VLAN 1 and 401 with their queries reaching the switch through Gigabit
Ethernet1/0/11:
Switch# show ip igmp snooping querier
Vlan
-------------------------------------------------------------
1
401
OL-19720-02
IP Address IGMP Version
1.1.1.1 v2
41.41.41.1 v2
ports
-----
Gi1/0/11(dynamic), Gi1/0/12(dynamic)
Gi1/0/11(dynamic), Gi1/0/12(dynamic)
Group Type Version
228.1.5.1 igmp v2
228.1.5.2 igmp v2
Interface
IP Address IGMP Version
1.1.1.1 v2
41.41.41.1 v2
Understanding Flex Links and the MAC Address-Table Move Update
Port
Gi1/0/11
Gi1/0/11
Port List
Gi1/0/11, Gi1/0/12, Gi2/0/11
Gi1/0/11, Gi1/0/12, Gi2/0/11
Backup Interface State
Port
Gi1/0/11
Gi1/0/11
Catalyst 2975 Switch Software Configuration Guide
19-5