Troubleshooting Cisco Switch Supervisor Handshake Timeout Issue

Few days back, i was working on a 4500 switch standby SUP replacement when i stumble upon an unknown issue. When inserting new supervisor module in standby slot, it is coming to COLD State which should be the ideal case.

After analysing the logs, i found “C4K_REDUNDANCY-2-HANDSHAKE_TIMEOUT_ACTIVE: The handshake messaging between active and standby has not yet started

Excerpt of #sh mod and # sh log

#sh mod

Mod  Redundancy role     Operating mode      Redundancy status

—-+——————-+——————-+———————————-

1   Active Supervisor   SSO                 Active

2   Standby Supervisor  SSO                 Disabled

%C4K_REDUNDANCY-2-HANDSHAKE_TIMEOUT_ACTIVE: The handshake messaging between active and standby has not yet started.

Explanation  :  The initial handshake message exchange between active and standby supervisor engines has not yet started. Traffic on the active supervisor engine is not affected, but supervisor engine redundancy will not work.
Solution: We need to reset and reseat active supervisor then insert standby. 
There are also other Supervisor errors you can get during replacement like : 
Case 2: 

Error Message    C4K_REDUNDANCY-2-HANDSHAKE_TIMEOUT_STANDBY: The handshake messaging between standby and active has not yet started.

Explanation    The initial handshake message exchange between standby and active supervisor engines has not yet started. If the active supervisor engine has not completed its initialization, this message may be seen temporarily on the standby supervisor engine. This condition will correct itself once the active supervisor engine initialization is complete. If problems persist after the active supervisor engine is initialized then redundancy will not work.