Overview of smart link

Smart link is a switch feature that provides effective, simple, and fast-converging link redundancy in network topology with dual uplink between different layers of the network. It requires an active (master) and a backup (slave) link. The active link carries the uplink traffic. Upon failure of the active link, a switchover is triggered and the traffic is directed to the backup link.

  • In the figure above, ports A1 and A2 are configured as part of a smart link group. The connection from the access switch to Distribution Switch A is the master, and the connection from the access switch to Distribution Switch B is the slave.

  • Only the master interface forwards traffic for a group of vlans (called a protected vlan group).

  • The other interface is in standby mode for this protected group. If port A1 goes down, port A2 starts forwarding traffic for this protected vlan group.

  • If port A1 comes back up, it goes to standby mode and does not forward traffic. Port A2 continues forwarding traffic. This is the case if preemption-mode is configured as “role”. If preemption-mode is not configured as “role”, when the master (A1) comes back up, it becomes Active (forwarding) after the configured ‘preemption-delay’.

  • Since a smart link group has it’s configuration information readily available for which port should be forwarding for the protected vlan group in the case of the active link failure, failover is much quicker than with STP.