Implementing Hardware and Software Redundancy on Modular Switches
Failure with SRM and SSO

When the switch is powered on, SRM with SSO runs between the two Supervisor Engines. The Supervisor Engine that boots first becomes the active Supervisor. The Multilayer Switch Feature Card 3 MSFC3 and Policy Feature Card 3 PFC3 become fully operational.

If the active Supervisor Engine 720 or MSFC3 fails, the redundant Supervisor Engine 720 and MSFC3 become active. The newly active Supervisor Engine 720 uses the existing PFC3 Layer 3 switching information to forward traffic while the newly active MSFC3 builds its routing table.

The routing protocols have to establish connectivity with their neighbor or peers and the Routing Information Base is built. During this time packet forwarding cannot take place.