Switch Stack Bridge Id And Router Mac Address - Cisco WS-C3750-48PS-S Software Configuration Manual

Chapter 5 Managing Switch Stacks
5.
6.
A stack master retains its role unless one of these events occurs:
•
•
•
•
•
In the events marked by an asterisk (*), the current stack master might be re-elected based on the listed
factors.
When you power on or reset an entire switch stack, some stack members might not participate in the
stack master election. Stack members that are powered on within the same 10-second time frame
participate in the stack master election and have a chance to become the stack master. Stack members
that are powered on after the 10-second time frame do not participate in this initial election and only
become stack members. All stack members participate in re-elections. For all powering considerations
that affect stack-master elections, refer to the "Switch Installation" chapter in the hardware installation
guide.
The new stack master becomes available after a few seconds. In the meantime, the switch stack uses the
forwarding tables in memory to minimize network disruption. The physical interfaces on the other
available stack members are not affected while a new stack master is elected and is resetting.
If a new stack master is elected and the previous stack master becomes available, the previous stack
master does not resume its role as stack master.
As described in the hardware installation guide, you can use the Master LED on the switch to see if the
switch is the stack master.

Switch Stack Bridge ID and Router MAC Address

The bridge ID and router MAC address identify the switch stack in the network. When the switch stack
initializes, the MAC address of the stack master determines the bridge ID and router MAC address.
If the stack master changes, the MAC address of the new stack master determines the new bridge ID and
router MAC address.
78-16180-02
cryptographic EMI for Cisco IOS Release 12.1(19)EA1 or later, the switch running the SMI is
selected as the stack master. This occurs because the switch running the cryptographic EMI takes 10
seconds longer to start than does the switch running the SMI. The switch running the EMI is
excluded from the master election process that lasts 10 seconds. To avoid this problem, upgrade the
switch running the SMI to a software release later than Cisco IOS Release 12.1(11)AX or manually
start the master switch and wait at least 8 seconds before starting the new member switch.
The switch with the longest system up-time.
The switch with the lowest MAC address.
*
The switch stack is reset.
The stack master is removed from the switch stack.
The stack master is reset or powered off.
The stack master has failed.
The switch stack membership is increased by adding powered-on standalone switches or switch
*
stacks.
Catalyst 3750 Switch Software Configuration Guide
Understanding Switch Stacks
5-5