Administrator Guide

240 Stacking
• Remove all the member ports of any Port-Channels (LAGs) so there will
not be any control traffic destined to those ports connected to this member.
• Statically re-route any traffic going through this unit.
When a unit in the stack fails, the stack master removes the failed unit from
the stack. The failed unit reboots with its original running-config. If the stack
is configured in a ring topology, then the stack automatically routes around
the failed unit. If the stack is not configured in a ring topology, then the stack
may split, and the isolated members will reboot and re-elect a new stack
master. No changes or configuration are applied to the other stack members;
however, the dynamic protocols will try to reconverge as the topology could
change because of the failed unit.
If you remove a unit and plan to renumber the stack, issue a no member unit
command in Stack Configuration mode to delete the removed switch from
the configured stack member information.
How is the Firmware Updated on the Stack?
When adding a new switch to a stack, the Stack Firmware Synchronization
feature, if enabled, automatically synchronizes the firmware version with the
version running on the stack master per the configuration on the master
switch. The synchronization operation may result in either upgrade or
downgrade of firmware on the mismatched stack member. Use the boot auto-
copy-sw command to enable stack firmware synchronization.
Upgrading the firmware on a stack of switches is the same as upgrading the
firmware on a single switch. After downloading a new image by using the File
Download page or copy command, the downloaded image is distributed to all
the connected units of the stack. For more information about downloading
and installing images, see "Images and File Management" on page 511.
What is Stacking Standby?
The standby unit may be pre-configured or automatically selected. If the
current stack master fails, the standby unit becomes the stack master. If no
switch is pre-configured as the standby unit, the software automatically
selects a standby unit from among the existing stack units.
When the failed master resumes normal operation, it joins the stack as a
member (not as the master) if the new stack master has already been elected.