Remove switch 3 from 5 x 3850 stack

[hmc2500]

We have a stack of 5 x 3850 switches.  3 switches are model WS-C3850-48T and 2 are model WS-C3850-24XS.

Stack:

Switch 1 - 3 WS-C3850-48T

Switch 4 - 5 WS-C3850-24XS

The stack also has stack power (2 rings) configured. 

We would like to remove Switch 3 from the stack. What is the proper way to remove switch 3 and reconnecting the cables?

[Enes Simnica]

hello @hmc2500 and based on ur stack configuration, u have a healthy 5-switch stack with three 48T models (Switches 1-3) and two 24XS models (Switches 4-5). The stack-power shows adequate available power (1140W for the main stack), so removing Switch 3 shouldn't cause power issues. If u can verify the current stack topology with the show switch detail, and show stack-power detail.

Before physically removing Switch 3, you'll want to prepare the stack by reconfiguring the connections. Since your topology shows a ring configuration (Switch 1 -  2 - 3 - 4 - 5 - 1), u'll need to maintain the ring after removal: 

• Switch 4 will now be connected between Switch 2 and Switch 5
• The remaining switches will renumber if needed (optional)
• The standby switch may change

and if u want to clean up the config, just remove any switch-specific configs for switch 3 with the,: switch 3 renumber 1, and no switch 3 provision ws-c3820-48t...

The entire process should take less than 5 minutes with minimal disruption, as the 3850 supports hot removal. The stack will briefly reconverge (typically 1 minute) as it adjusts to the new topology. HOPE THE ANSWER IS NOT THAT LONG, AND HOPE IT HELPS...

https://www.cisco.com/en/US/docs/switches/lan/catalyst3850/software/release/3se/consolidated_guide/b_consolidated_3850_3se_cg_chapter_01101101.html

-Enes

[pieterh]

@Enes Simnica 's post contains valuable information, read that carefully

broken down into individual steps it will be:
( added later: evacuate all networkconections away from switch-3, (if not already done))
- power down switch 3
- reconfigure cabling power-stack-1    1 -  2 - 3 - 4 - 5 - 1 -> 1 -  2  - 4 - 5 - 1
- reconfigure cabling power-stack-11  1 -  2 - 3 - 4 - 5 - 1 -> 1 -  2  - 4 - 5 - 1
- reconfigure cabling data-stack          1 -  2 - 3 - 4 - 5 - 1 -> 1 -  2  - 4 - 5 - 1
- reconfigure the stack configuration (on the stack-master)
   no switch 3 provision ws-c3820-48t... (+ save configuration)
- NB! switch-4 remains switch-4 after changing cables, even after reboot
   if desired renumber switch 4 and 5. NB! requires reboot to effectuate,
   switch 4 renumber 3   (portnumbers will be renumbered after reboot Gi4/0/1 -> Gi3/0/3 etc.)
   switch 5 renumber 4  (same 5 -> 4 ))

perform the following actions on switch-3
- power-on (stand-alone no network)
- erase configuration
   write erase   
- NB write erase will, not renumber switch-3 to number-1, therefore command below
   switch 3 renumber 1

[balaji.bandi]

what is the reason of removing switch ?

do you want to remove with out any downtime ?

best is take downtime and re-arrange the switch numbers / priority and stack cable for Long term

also if any upgrade required perform in same maintenance window.

[hmc2500]

Management would like to consolidate the used ports and get rid of hardware that is no longer required. It's a 24x7 datacenter, so we have to minimize downtime as much as possible. POE is not used much.

[balaji.bandi]

Then you can move all the connected links to different switch, and safe remove and adjust the stack cable. since POE not required, easy to remove the switch.

you see error when show switch (member 3 removed)

but when you get downtime adjust the switch numbers and reboot will fix that issue (other wise just cosmetic)

[paul driver]

Hello
By the looks of it sw3 is in a power stack in sharing mode and has the most power being consumed - if you do drop that switch the stack poe devices may not continue to function  

as for the removal of the switch itself - obviously you need to be aware if it has port related to any trunk/port channels etc.. as they will be lost also