how does vss handle loss of switch

[carl_townshend]

Hi There

can anyone tell me how a 6509 pair handles the loss of the other vss switch, and what happens when the other comes back on ?

cheers

[Arumugam Muthaiah · Accepted solution]

Hi Carl,

• If the VSS active chassis or supervisor engine fails, the VSS initiates a stateful switchover (SSO) and the former VSS standby supervisor engine assumes the VSS active role. The failed chassis performs recovery action by reloading the supervisor engine.
  
• If the VSS standby chassis or supervisor engine fails, no switchover is required. The failed chassis performs recovery action by reloading the supervisor engine.
  
• The VSL links are unavailable while the failed chassis recovers. After the chassis reloads, it becomes the new VSS standby chassis and the VSS reinitializes the VSL links between the two chassis.
  
• The switching modules on the failed chassis are unavailable during recovery, so the VSS operates only with the MEC links that terminate on the VSS active chassis. The bandwidth of the VSS is reduced until the failed chassis has completed its recovery and become operational again. Any devices that are connected only to the failed chassis experience an outage.
  

Refer:

https://supportforums.cisco.com/thread/2003430

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vss.html#wp1083292

Regards,

Aru

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