Controller-less WLANs

What is Pot-master state of an Instant AP?

Potential-master state kicks in when the existing Master goes down or becomes unreachable.

  1. The IAP waits for election wait time to move from slave to Potential master.
  2. If it hears any beacon during this time, it moves back to salve.
  3. If it does not hear any master beacon it becomes a potential master.
  4. As soon as an IAP becomes a potential master, it starts sending Master-beacon as Broadcast packets in the subnet. These packets are sent with a parameter mentioning that these packets are being sent by a pot-master.
  5. Pot-master also tries to reach the last known master through unicast messages for the election wait time.
  6. If the previous master is still not reachable and the election wait time is over, it transitions into the Master.

Environment : When Multiple IAPs are part of the same subnet and on failure of master a slave transitions to Pot-master and then to Master.

 

Master election process is built in to the code. No specific configuration required.

 

As the AP becomes a Pot-master, it starts sending Master beacon with pot-master flag state set. Below master election related messages can be seen by using “debug-master-beacon”.

 

rtaImage.jpg

 

Potential master also tries to reach its last known Master through unicast (00:24:6c:cb:a5:3f).

 

rtaImage (1).jpg

 

rtaImage (2).jpg

 

In the above screen shot it can been seen that  events “Slave->Pot-Master : 1 time” and “Pot-master->Master: 1 time” have taken place once each.

Troubleshooting can be done using command "debug-master-beacon", "show election" and "show summary"

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‎07-03-2014 07:30 PM
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