Cisco Systems NME-16ES-1G manual Stack Master Election and Re-Election

Cisco EtherSwitch Service Modules Feature Guide

Information About the Cisco EtherSwitch Service Modules

	A standalone Cisco EtherSwitch service module or Catalyst 3750 switch is a switch stack with one stack
	member that also operates as the stack master. You can connect one standalone Cisco EtherSwitch
	service module to another Cisco EtherSwitch service module or Catalyst 3750 switch to create a switch
	stack containing two stack members, with one of them being the stack master. You can connect
	standalone modules to an existing switch stack to increase the stack membership.
	If you replace a stack member with an identical model, the new Cisco EtherSwitch service module or
	Catalyst 3750 switch functions with exactly the same configuration as the replaced Cisco EtherSwitch
	service module, assuming that the new Cisco EtherSwitch service module or switch is using the same
	member number as the replaced Cisco EtherSwitch service module or switch.
	The operation of the switch stack continues uninterrupted during membership changes unless you
	remove the stack master or you add powered-up standalone Cisco EtherSwitch service modules or
	switches.
Note	• Make sure the Cisco EtherSwitch service modules or Catalyst 3750 switches that you add to or
	remove from the switch stack are powered off.
	• After adding or removing stack members, make sure that the switch stack is operating at full
	bandwidth (32 Gbps). Press the Mode button on a stack member until the Stack mode LED is on.
	The last two port LEDs on all Cisco EtherSwitch service modules in the stack should be green.
	Depending on the Cisco EtherSwitch service module model, the last two ports are either
	10/100/1000-Mbps ports or small form-factor pluggable (SFP) service module ports. If, on any of
	the modules, one or both of the last two port LEDs are not green, the stack is not operating at full
	bandwidth.

Adding powered-up modules (merging) causes the stack masters of the merging Cisco EtherSwitch service module stacks to elect a stack master from among themselves. The re-elected stack master retains its role and configuration and so do its stack members. All remaining modules, including the former stack masters, reload and join the switch stack as stack members. They change their stack member numbers to the lowest available numbers and use the stack configuration of the re-elected stack master.

Stack Master Election and Re-Election

The stack master is elected or re-elected based on one of these factors and in the order listed:

1.The Cisco EtherSwitch service module or Catalyst 3750 switch currently the stack master

2.The Cisco EtherSwitch service module or Catalyst 3750 switch with the highest stack member priority value

Note We recommend assigning the highest-priority value to the Cisco EtherSwitch service module or Catalyst 3750 switch that you prefer to be the stack master. This ensures that the Cisco EtherSwitch service module or Catalyst 3750 switch is re-elected as stack master if a re-election occurs.

3.The Cisco EtherSwitch service module or Catalyst 3750 switch not using the default interface-level configuration

4.The Cisco EtherSwitch service module or Catalyst 3750 switch with the higher-priority service module or switch version

Cisco IOS Release 12.2(25)SEC

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