User Manual

M4300 Intelligent Edge Series Fully Managed Stackable Switches
Manage Stacking User Manual165
Upgrading the firmware on a stack of switches is the same as upgrading the firmware on a
single switch. After you download a new image by using the File Download page or SCC, the
downloaded image is distributed to all the connected units of the stack.
Note: We recommend that you set the active image for all stack members
the same as the active image of the stack master. In other words, if
image1 is the active image on the stack master, all units must use
image1 as the active image. For information about configuring the
active image, see Configure Dual Image Settings on page 684.
Stack Configuration Maintenance
The stack master stores and maintains the saved and running configuration files for the
switch stack. The configuration files include the system-level settings for the switch stack and
the interface-level settings for all stack members. Each stack member retains a copy of the
saved file for backup purposes. If the master is removed from the stack or becomes
unavailable, another member is elected master and then runs from that saved configuration.
The switch master copies its running configuration to the stack member configured as the
standby unit whenever it changes (subject to some restrictions to reduce overhead).
This
enables the standby unit to take over the stack operation with minimal interruption if the stack
master becomes unavailable. The running-config synchronization also occurs when the
running configuration is auto-saved on the stack master or when the standby unit changes.
Stack Master Election
All stack members are eligible stack masters. If the stack master becomes unavailable, the
remaining stack members participate in electing a new stack master from among themselves.
The following factors determine which switch is elected the stack master:
• The switch that is master always has priority to retain the role of master
.
• Assigned priority
.
• MAC address.
When the stack is powered up and completes the boot process or the original stack master
becomes unavailable, the stack master is determined through an election process.
The rules for stack master election are as follows:
• If a unit was elected stack master previously
, then it remains the stack master and other
units are stack members.
• If no units were stack masters, or more than one unit was a stack master
, then the unit
with the highest management preference is elected stack master. The management