SCENARIO:
Two Cisco 3750 series switches in stack.
Master C3750G-48TS
Slave C3750-24TS

GOAL:
Replace slave switch (C3750-24TS) with another slave C3750G-48TS switch witch has the same version of IOS as master switch. In the end we have 2 equal switches in rack. More interfaces and faster speed on second switch.

HOW TO DO IT:
1. backup all configurations

# copy running-config tftp

2. prepare configuration for interfaces witch where on 24 port switch for 48 port giga switch (in config replace FastEthernet with GigaEthernet)
3. write down cable arrangement (from patch panel to switch)
4. shutdown slave switch (unplug electrical cable)
5. remove stack cable(s) from slave switch
6. remove utp cables from switch
6. remove slave switch from rack
7. add new slave switch to rack
8. reconnect stack cables to new switch
9. power on new switch
10.reconnect utp cables,…
11. repair configuration on stack for newly added interfaces
12. check if everything is working as it should with;

# sh stack ...
# sh int bri
# ping ...