The Certified Geek

In a normal switch stack of Cisco Catalyst 3750 (several switches connected with each other functioning as one virtual switch), one switch will make itself the master switch (the one which controls the operations of the stack). In order to make the switch elect itself as master, it needs to have the highest priority number.

Here we have a switch with a priority “1″

Switch#show switch
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
*1 Master 0023.344b.de80 1 0 Ready


We need to increase its priority number in order to force it to become the master when it joins the switch stack

Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#switch 1 ?
priority Set the priority of the specified switch
provision Configure Switch provision / offline config
renumber Renumber the specified switch number

Switch(config)#switch 1 priority 15
Changing the Switch Priority of Switch Number 1 to 15
Do you want to continue?[confirm]
New Priority has been set successfully


For here, we can check the switch status and priority number set to “15″

Switch#sh switch
Switch/Stack Mac Address : 0023.344b.de80
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
*1 Master 0023.344b.de80 15 0 Ready


When this stack is joined in a switch stack, it will elect itself as the switch master (check the Master LED after booting). Note that the switch stack can only handle only 9 stacked switches, so priority number 15 should be more than enough. Then the only problem if somebody set another switch with priority number 15 too, we will check on that later