LAB: FLex LInks

Flex Links feature is used as an alternative to Spanning-Tree Protocol in
environments where physical loops occur in the layer 2 network
- The backup link operates in standby mode, and waits for the line protocol of the active link to go down. If the line protocol of the active link is down, the backup link becomes active and immediately starts forwarding. When the active link’s line protocol status comes back up, the backup link goes back into standby state and stops forwarding traffic.


SW1:

interface Port-channel1
switchport trunk encapsulation dot1q
switchport mode trunk
switchport backup interface Fa0/16
switchport backup interface Fa0/16 preemption mode forced
switchport backup interface Fa0/16 preemption delay 20
!
interface FastEthernet0/13
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface FastEthernet0/14
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface FastEthernet0/16
switchport trunk encapsulation dot1q
switchport mode trunk

SW2:

interface Port-channel1
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/13
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface FastEthernet0/14
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface FastEthernet0/16
switchport trunk encapsulation dot1q
switchport mode trunk

SW3:

interface FastEthernet0/13
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/16
switchport trunk encapsulation dot1q
switchport mode trunk


verification:

SW1#show interfaces po1 switchport backup
Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
Port-channel1 FastEthernet0/16 Active Up/Backup Standby