Examples
This example shows how to configure two interfaces as Flex Links:
Switch# configure terminal
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2
Switch(conf-if)# end
This example shows how to configure the Fast Ethernet interface to always preempt the backup:
Switch# configure terminal
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 preemption forced
Switch(conf-if)# end
This example shows how to configure the Fast Ethernet interface preemption delay time:
Switch# configure terminal
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 preemption delay 150
Switch(conf-if)# end
This example shows how to configure the Fast Ethernet interface as the MMU primary VLAN:
Switch# configure terminal
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 mmu primary vlan 1021
Switch(conf-if)# end
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 Backup Interface State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Up/Backup Up
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 Backup Interface State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Down/Backup Up
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 Backup Interface State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Up/Backup Up
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 Backup Interface State
------------------------------------------------------------------------
FastEthernet0/3 FastEthernet0/4 Active Down/Backup Up
Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Preemption Mode : off
Bandwidth : 10000 Kbit (Fa0/3), 100000 Kbit (Fa0/4)
Mac Address Move Update Vlan : auto
Thanks,
satish
