Adding a switch to a live stack

[ollie1]

What sort of impact if any does adding another switch into a stack that is currently live have? The work is being completed out of hours in case of any downtime but i'm assuming the switch should just grab config from the master and recognise the priority of the master switch and take member status, is this correct? No cpnfig has been done on the new switch other than a firmware upgarde to match the current stack firmware..

Thank you in advance!

[balaji.bandi]

Here is the steps used daily basis : ( never seen any downtime, but suggest to do in maintenance window.)

01- Check Switch-1 image version, switch number and priority
02- Verify that the new switch (2 or 3) has the same IOS as Switch-1,"x.x.bin" if not update the image
03- Renumber the new switch to 2 or 3 cmd: switch1 renum switch2 or 3 and change the priority to 7(less than maser)

example :  switch 3 priorty 7
04- Add provision to the existing switch by

 switch 3 provision WS-C3750X-48PF-S  << reference for 3750
05- Turn off Switch-3

Online Steps :

06- Mount the new Switch into the cabinet or rack
07- Make sure all stack-wise cable are tightly connected as well as stack-power cable before proceed
08- Remove one stack-wise cable from switch-2 (last switch) and connect to switch-3, also connect switch-2 and switch-3 with stack-wise cable
09- Remove one stack-power cable from switch-2 and connect to switch-3, also connect switch-2 and switch-3 with stack-power cable
10- Power up switch-3
11- Check stack connections are up, switch numbers and priorities

# Show Switch
12- Check the running config by show running config command and ensure it has the same config as the existing switch.
14- Save the config.

[Leo Laohoo]

If done right, no impact.
1. Make sure the new switch has the exact same IOS version and license as the rest of the entire stack.
2. DO NOT APPLY POWER to the new switch.
3. Connect the stacking cable.
4. Apply power.
5. Once the new switch has joined the stack, configure the switch priority.

[Arshad Safrulla]

Above methods suggested are the best to go. Just to add most of the IOS-XE supported switches support software auto upgrade feature. Master switch will push the correct IOS to the new switch if it see's that it is trying to join the stack with a different IOS. So you dont have to go through the hassle of IOS upgrade.

On 2960-x auto upgrade is enabled by default.

!

conf t

 software auto-upgrade enable

!

Useful link - https://community.cisco.com/t5/networking-documents/using-the-auto-upgrade-feature-on-the-cisco-catalyst-3850/ta-p/3140319