Cisco catalyst 3750 Command Reference Manual page 865

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
switchport backup interface
When a Flex Link interface comes up, VLANs preferred on this interface are blocked on the peer
interface and moved to the forwarding state on the interface that has just come up. In this example, if
interface Gi1/0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi1/0/8
and forwarded on Gi1/0/6.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/6 GigabitEthernet1/0/8 Active Up/Backup Up
Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120
Catalyst 3750 Switch Command Reference
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