Cisco Catalyst 3560-X Software Configuration Manual page 649

Chapter 1 Configuring Flex Links and the MAC Address-Table Move Update Feature
In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the switch:
Switch(config)#interface gigabitethernet 2/0/6
Switch(config-if)#switchport backup interface gigabitethernet 2/0/8 prefer vlan 60,100-120
When both interfaces are up, Gi2/0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi2/0/6
forwards traffic for VLANs 1 to 50.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
GigabitEthernet2/0/6
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
------------------------------------------------------------------------
GigabitEthernet2/0/6
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 Gi2/0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi2/0/8
and forwarded on Gi2/0/6.
Switch# show interfaces switchport backup
Switch Backup Interface Pairs:
Active Interface
------------------------------------------------------------------------
GigabitEthernet2/0/6
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
------------------------------------------------------------------------
FastEthernet1/0/3
Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Preemption Mode
Bandwidth : 10000 Kbit (Fa1/0/3), 100000 Kbit (Fa1/0/4)
Mac Address Move Update Vlan : auto
OL-25303-03
Backup Interface
GigabitEthernet2/0/8
Backup Interface
GigabitEthernet2/0/8
Backup Interface
GigabitEthernet2/0/8
Backup Interface
FastEthernet1/0/4
: off
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
Configuring Flex Links and MAC Address-Table Move Update
State
Active Up/Backup Standby
State
Active Down/Backup Up
State
Active Up/Backup Standby
State
Active Down/Backup Up
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