All stack members must run the same 200 Series software version to ensure compatibility between stack members. The software versions on all stack members, including the stack manager, must be the same. This helps ensure full compatibility in the stack protocol version among the stack members.
If a stack member is running a software version that is not the same as the stack manager, then the stack member joins the stack but stays in code incompatible status (the stack unit is not allowed to join the stack as a fully functional member). Use the show switch command to list the stack members and the software versions. The new unit will be visible. The administrator can load the code to that new unit and reboot the unit. The ports on the unit in software mismatch state do not come up.