Switch Stack Configuration Files - Cisco WS-C3750-48PS-S Software Configuration Manual

Understanding Switch Stacks
Major Incompatibility Between Switches
Switches with different Cisco IOS software versions likely have different stack protocol versions.
Switches with different major stack protocol version numbers are incompatible and cannot exist in the
same switch stack.
Minor Incompatibility Between Switches
Switches with the same major version number but a different minor version number as the stack master
are considered partially compatible. When connected to a switch stack, partially compatible switches
enter into version mismatch (VM) mode and cannot join the stack. The stack master downloads the
software version it is using to any switch in VM mode.
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The port LEDs on switches in VM mode remain off and pressing the Mode button does not change the
LED mode.
You can also use the show switch user EXEC command to see if any stack members are in VM mode.

Switch Stack Configuration Files

The configuration files record these settings:
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The stack master has the saved and running configuration files for the switch stack. All stack members
periodically receive synchronized copies of the configuration files from the stack master. If the stack
master becomes unavailable, any stack member assuming the role of stack master has the latest
configuration files.
Note We recommend that all stack members are installed with Cisco IOS Release 12.1(14)EA1 or later to
ensure that the interface-specific settings of the stack master are saved, in case the stack master is
replaced without saving the running configuration to the startup configuration.
When a new, out-of-box switch joins a switch stack, it uses the system-level settings of that switch stack.
If a switch is moved to a different switch stack, that switch loses its saved configuration file and uses the
system-level configuration of the new switch stack.
Catalyst 3750 Switch Software Configuration Guide
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If there is a stack member that is not in VM mode and is running software that can also run on the
switch in VM mode, the stack master uses that software to upgrade (or downgrade) the software on
the switch in VM mode. The switch in VM mode automatically reloads and joins the stack as a fully
functioning member.
The stack master does not automatically install EMI software on an SMI-running switch or SMI
software on an EMI-running switch.
If none of the stack members are running software that can be installed on the switch in VM mode,
the stack master scans the switch stack to see if there are any other recommended actions.
Recommended actions appear in the system message log. If there are no other actions to try, the
stack master displays the recommended action to upgrade the software running on the switch stack.
System-level (global) configuration settings—such as IP, STP, VLAN, and SNMP settings—that
apply to all stack members
Stack member interface-specific configuration settings, which are specific for each stack member
Chapter 5 Managing Switch Stacks
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