Flex Links

Flex Links are a pair of a Layer 2 interfaces (switchports or port channels), where one interface is
configured to act as a backup to the other. Flex Links are typically configured in service-provider or
enterprise networks where customers do not want to run STP. Flex Links provide link-level redundancy
that is an alternative to Spanning Tree Protocol (STP). STP is automatically disabled on Flex Links
interfaces.
To configure the Flex Links feature, you configure one Layer 2 interface as the standby link for the link
that you want to be primary. With Flex Links configured for a pair of interfaces, only one of the
interfaces is in the linkup state and is forwarding traffic. If the primary link shuts down, the standby link
starts forwarding traffic. When the inactive link comes back up, it goes into standby mode.

Configuring Flex Links
Flex links