Stack switch replacement with different model switch.

[CiscoAAA1]

Hi, 

  I have two  WS- c3750x-48T -L switches stacked - connected back to back with  Stack cable. 

Now one of the switch failed and I have only  WS- c3750X- 12 S stackable switch as SPARE  with me. 

So can replace 48 Port with 12 Port ?  Does it need any new configuration 

If so  what will  happen to the additional configuration of the current stack master. ( I mean 13 to 48 in current switch)

Regards,

AAA

[pman]

Hi,

You can create a stack with different models.

"A Cisco 3750 switch can be stacked with any other model of Cisco 3750 switches.
Catalyst 3750 switches that run Cisco IOS®Release 12.2(25)SEB are compatible with Cisco EtherSwitch service modules that run Cisco IOS Release 12.2(25)EZ.
Catalyst 3750 switches and Cisco EtherSwitch service modules can be in the same switch stack.
Within this switch stack, the Catalyst 3750 switch or the Cisco EtherSwitch service module can be the stack primary."

But note that switches with different major version numbers are incompatible and cannot exist in the same switch stack.

Attach information on the subject:

Major Version Number Incompatibility Among Switches

Switches with different Cisco IOS software versions likely have different stack protocol versions. Switches with different major version numbers are incompatible and cannot exist in the same switch stack.

Minor Version Number Incompatibility Among Switches

Switches with the same major version number but with a different minor version number as the stack master are considered partially compatible. When connected to a switch stack, a partially compatible switch enters version-mismatch (VM) mode and cannot join the stack as a fully functioning member. The software detects the mismatched software and tries to upgrade (or downgrade) the switch in VM mode with the switch stack image or with a tar file image from the switch stack flash memory. The software uses the automatic upgrade (auto-upgrade) and the automatic advise (auto-advise) features.

https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/71925-cat3750-create-switch-stks.html#toc-hId--622058967

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_44_se/configuration/guide/scg/swstack.html#wp1166394

[balaji.bandi]

You can add new 12S for the existing stack

new switch should be save version of Code what master running.

remove the faulty one add new one - you may see port information difference, for that you can choose different switch number. and different priority.

you see some warning about the old switch, but when later get chance to reboot whole stack, all will be settle down.

as i remember 12S all SFP ports not copper so you need Copper GLC-T for all the ports to use.

Other suggestion : there are lots of used switch available in the market, since 3750X  end of life, you get for less price.