Kindly find the answer inline:
-- Adding an additional supervisor (w/c will be in Active-Standby) is simply opening a slot and inserting the 2nd one - See more at: https://supportforums.cisco.com/discussion/12339266/redundant-supervisors-what-do-when-i-want-maintain-one-supervisor#sthash.6dl4gvgK.dpuf
Answer: Yes, you can add a new supervisor in an up and running switch, without disturbing the current operational status of the switch.
Question:HOWEVER, what If I want to maintain one of the supervisors? Example I want to remove the current active supervisor:
If you remove current active supervisor and the standby is in "standby hot" state, it should not impact the switch, the standby sup should become the Active supervisor and the traffic should not be impacted.
however, if the standby is not in the standby hot, and is in RPR or standby cold state, there would be impact.
Hence it is recommended, as a best practice we must not bring down/remove the Active supervisor,
We can follow following steps:
-- Perform force-switchover.
-- Let the standby sup become active.
-- Verify the health state of the switch.
-- Verify the traffic status, once all seems to be working.
-- Then proceed with the removal of the standby supervisor, previously active sup.
-- Perform the desired steps.
-- Insert the Sup module back in the chassis, since you want the Old Active Sup to become Active, you can follow these steps:
-- Verify the diagnostic status of the inserted sup module.
-- Verify the redundancy status.
-- Once all looks good.
-- You can again perform force-switchover.
# show module
# show redundancy
# show diagnostic result module all
#show diagnostic result module X failure