Cisco Catalyst 2960 Command Reference Manual page 574

switchport backup interface
The following example shows how to configure preferred VLANs:
Switch(config)# interface gigabitethernet 0/6
Switch(config-if)# switchport backup interface gigabitethernet 0/8 prefer vlan 60,100-120
You can verify your setting by entering the show interfaces switchport backup privileged EXEC
command.
In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the switch:
Switch(config)# interface gigabitEthernet 0/6
Switch(config-if)# switchport backup interface gigabitEthernet 0/8 prefer vlan 60,100-120
When both interfaces are up, Gi0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi0/6 forwards
traffic for VLANs 1 to 50.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
GigabitEthernet0/6
Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120
When a Flex Link interface goes down (LINK_DOWN), VLANs preferred on this interface are moved
to the peer interface of the Flex Link pair. In this example, if interface Gi0/6 goes down, Gi0/8 carries
all VLANs of the Flex Link pair.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
GigabitEthernet0/6
Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120
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 Gi0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi0/8 and
forwarded on Gi0/6.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
GigabitEthernet0/6
Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120
Switch# show interfaces switchport backup detail
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
FastEthernet0/3
Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Catalyst 2960 Switch Command Reference
2-702
Backup Interface
GigabitEthernet0/8 Active Up/Backup Up
Backup Interface
GigabitEthernet0/8 Active Down/Backup Up
Backup Interface
GigabitEthernet0/8 Active Up/Backup Up
Backup Interface
FastEthernet0/4 Active Down/Backup Up
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
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