Cisco 3750G Configuration Guide - Page 133

Major Version Number Incompatibility Among Switches, Understanding Auto-Upgrade and Auto-Advise

Page 133 highlights

Chapter 5 Managing Switch Stacks Understanding 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 "Understanding Auto-Upgrade and Auto-Advise" section on page 5-11. 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. • 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. Note A switch in VM mode might not run all released software. For example, new switch 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. OL-8550-02 Catalyst 3750 Switch Software Configuration Guide 5-11

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5-11
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 5
Managing Switch Stacks
Understanding 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
“Understanding Auto-Upgrade and Auto-Advise” section on page 5-11
.
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.
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.
Note
A switch in VM mode might not run all released software. For example, new switch
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.