The Certified Geek

Imagine you have a number of Cisco Wireless Access Points, say 10 spread across your office functioning as some wireless mesh. You need to replace an access point (AP) which giving some problem on the wireless infrastructure. However, you currently dont have any documentation on which APs are mounted on the ceiling. There are also no proper labelling. So, how would you determine which physically is the device?

Cisco IOS has a command which make the LED of the AP to blink in order to be identified from the pack.

ap#led flash ?
<1-3600> number of sec to flash
disable stop flashing the LEDs

ap#sh led flash
LED Flash is disabled

ap#led flash
ap#sh led flash
LED Flash is enabled


With this command, you can physically locate the APs from the ceiling.

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