A switch stack is a set of up to nine Catalyst 3750 switches connected through their StackWise ports. We can stack up to nine 3750 switches of different models. When introducing a new switch to a stack, make sure that it is running the same software version as the master switch to avoid version mismatch. All stack members must run the same Cisco IOS software version to ensure compatibility between stack members. This helps ensure full compatibility in the stack protocol version among the stack members. Software Compatibility can be verified by issuing the command “show platform stack-manager all”
With 3750 switches, you can mix and match any model you want and stack them together but it must run the same code with same feature set. If a switch becomes the new master, that switch should support same feature set as the master or else you will have inconsistency.
The Cisco Catalyst 3750 series switches use Switch Database Management (SDM) templates to optimize the system resources for specific features dependent on how the switch is used in the network. There are two versions of the SDM templates: Desktop and Aggregator. The 3750-12S switch alone supports both templates. All other model switches of the 3750 series support only the Desktop version.
When a Cisco Catalyst 3750 switch stack consists of 3750-12S and other models, make sure to use only the Desktop SDM template.