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Cisco IE 3010 Switch Software Configuration Guide
OL-23145-01
Chapter 20 Configuring Flex Links and the MAC Address-Table Move Update Feature
Understanding Flex Links and the MAC Add ress-Table Move Update
1 228.1.5.1 igmp v2 Fa0/1, Fa0/2, Fa0/3
1 228.1.5.2 igmp v2 Fa0/1, Fa0/2, Fa0/3
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 on ly on FastEthernet0/1,
because the backup port FastEthernet0/2 is blocked. When the active link, FastEthe rnet0/1, goes down,
the backup port, FastEthernet0/2, begins forwarding.
As soon as this port starts forwarding, the switch sends proxy r eports 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 mult icast
data. This is the default behavior of Flex Link. This behavior changes when the user configures fast
convergence using the switchport backup interface FastEthernet0/2 multicast fast-convergence
command. This example shows how this feature is configure d:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface FastEthernet0/1
Switch(config-if)# switchport backup interface FastEthernet0/2 multicast fast-convergence
Switch(config-if)# exit
Switch# show interfaces switchport backup detail
Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
FastEthernet0/1 FastEthernet0/2 Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : Off
Bandwidth : 100000 Kbit (Fa0/1), 100000 Kbit (Fa0/2)
Mac Address Move Update Vlan : auto
This output shows a querier for VLAN 1 and 401 with their queries reaching the switch through the
configured port:
Switch# show ip igmp snooping querier
Vlan IP Address IGMP Version Port
-------------------------------------------------------------
1 1.1.1.1 v2 Fa0/1
401 41.41.41.1 v2 Fa0/1
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 Fa0/1(dynamic), Fa0/2(dynamic)
401 Fa0/1(dynamic), Fa0/2(dynamic)
Similarly, both the Flex Link ports are a part of the learned groups. In this example, the port 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 Fa0/1, Fa0/2, Fa0/3
1 228.1.5.2 igmp v2 Fa0/1, Fa0/2, Fa0/3
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 the configured FastEthernet0/1, it is also leaked to the backup port FastEthernet0/2. The
upstream router learns the groups and starts forwarding multicast data, which is dropped at the ingress