Major Version Number Incompatibility Among Switches; Minor Version Number Incompatibility Among Switches; Understanding Auto-Upgrade And Auto-Advise - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Chapter 5 Managing Switch Stacks

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. For
more information, see the
To see if there are switches in VM mode, use the show switch user EXEC command. The port LEDs on
switches in VM mode will also stay off. Pressing the Mode button does not change the LED mode.
Beginning with Cisco IOS Release 12.35(SE), you can use the boot auto-download-sw global
configuration command to specify a pathname URL for the master switch to get an image in case of
version-mismatch.

Understanding Auto-Upgrade and Auto-Advise

When the software detects mismatched software and tries to upgrade the switch in VM mode, two
software processes are involved: automatic upgrade and automatic advise.
•
OL-8550-02
"Understanding Auto-Upgrade and Auto-Advise" section on page
The automatic upgrade (auto-upgrade) process includes an auto-copy process and an auto-extract
process. By default, auto-upgrade is enabled (the boot auto-copy-sw global configuration command
is enabled). You can disable auto-upgrade by using the no boot auto-copy-sw global configuration
command on the stack master. You can check the status of auto-upgrade by using the show boot
privileged EXEC command and by checking the Auto upgrade line in the display.
Auto-copy automatically copies the software image running on any stack member to the switch
–
in VM mode to upgrade (auto-upgrade) it. Auto-copy occurs if auto-upgrade is enabled, if there
is enough flash memory in the switch in VM mode, and if the software image running on the
switch stack is suitable for the switch in VM mode.
A switch in VM mode might not run all released software. For example, new switch
Note
hardware is not recognized in earlier versions of software.
Automatic extraction (auto-extract) occurs when the auto-upgrade process cannot find the
–
appropriate software in the stack to copy to the switch in VM mode. In that case, beginning with
Cisco IOS Release 12.2(35)SE, the auto-extract process searches all switches in the stack,
whether they are in VM mode or not, for the tar file needed to upgrade the switch stack or the
switch in VM mode. The tar file can be in any flash file system in the switch stack (including
the switch in VM mode). If a tar file suitable for the switch in VM mode is found, the process
extracts the file and automatically upgrades that switch.
The auto-upgrade (auto-copy and auto-extract) processes wait for a few minutes after the
mismatched software is detected before starting.
Catalyst 3750 Switch Software Configuration Guide
Understanding Switch Stacks
5-11.
5-11