Keepalive scenario

The following diagram illustrates a scenario in which both VSX switches are up, but the ISL link is down. The switches cannot exchange information.

The keepalive functionality brings down the link between Switch B and Switch C in the following diagram. The traffic is forced to go from Switch C to Switch A and then through the Layer 3 network to access Switch B. The keepalive path is over the Layer 3 network. Traffic traveling from Switch B to Switch A is also forced to go through the Layer 3 network.

Keepalive topology


Do not have the keepalive path go over ISL. Use a direct-link connection for keepalive. If the keepalive path uses ISL as its only path and an ISL link failure occurs, the VSX switches would be out of sync without the keepalive functioning.