Can any one advise about what will happen to my existing switch stack when adding an additional slave switch?

I'm trying to confirm whether this will cause a temporary outage to my network or will the master just auto update the new slave?


After doing some additional research and trolling Cisco.com i found that the slave should auto update/download from the master and start working, without causing an outage.

Adding New Members

When the switching stack has established a master, any new switch added afterward automatically becomes a subordinate. All the current routing and addressing information is downloaded into the subordinate so that it can immediately begin transmitting traffic. Its ports become identified with the IP address of the master switch. Global information, such as QoS configuration settings, is downloaded into the new subordinate member.'2'

'1' Creation and Management of Catalyst 3750 Switch Stacks'

'2' Cisco StackWise and StackWise Plus Technology.

Note: A new election will only happen if you add a new member that has a higher priority number than the master, to be on the safe side set the priority number to the same value as the last slave.


The newly added switch will be added as a slave - as long as it doesn't trigger a new master election through some sort of catastrophic issue, then you should be safe.

On the other hand, to be on the safe side I'd still recommend doing it off-hours, in the same way I'd suggest that for adding a new supervisor blade to a 6500 chassis - a change like that definitely carries some risk.


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