Controller-less WLANs

How is master IAP elected in an IAP cluster?

by on ‎07-02-2014 01:05 PM

Environment  :  Product and Software: This article applies to Aruba Instant Access Points (IAP's) running on Aruba InstantOS 6.2.0.0-3.2.0.0 and later.

 

 

Aruba Instant does not require an external mobility controller to regulate and manage the Wi-Fi network. Instead, one IAP in every network assumes the role of a Virtual Controller (VC).
 

The Master Election Protocol enables the Aruba Instant network to dynamically elect an IAP to take on a VC role. This protocol ensures stability of the network during initial startup or when the VC goes down by allowing graceful failover to a new Virtual Controller when the existing VC is down.

Below-mentioned is the brief description on the Election Process:


  • IAP boots up, stay in ‘INITIAL’ state for a while, if it receives any master beacon, it becomes slave.
  • If no master beacon received, transition to ‘Pot-Master’ state (Pot: Point of Time) and stay for a while. If it receives any master beacon during this period, trigger the conflict resolve algorithm to compute a new master.
  • If no master beacon received, transition to ‘Master’ state and start to broadcast master beacon. If it receives any master beacon during this period, trigger the conflict resolve algorithm to compute a new master.
  • At any time, if a slave do not hear master beacon for a while, it uses the same manner to do the transition.

IAP uses following order as Conflict Resolve Algorithm, to resolve conflicts:

  1. look into IP scope. IAP with default-ip cannot win
  2. look into 3G capability
  3. look into AP class, Arran (IAP-13x) gets higher priority
  4. look into uptime, older AP gets higher priority
  5. look into AP MAC, bigger address gets higher priority

NOTE: If it is a single IAP in the network running with default-ip, then it would take  the role of VC.

Normally, adding a new IAP into a cluster will not affect the existing Master, but again there are 2 exceptions to this rule as mentioned-below:
 
  • Master is running with default-ip, a new IAP comes up and gets DHCP address and thereby becomes the new Master. At the same time, any IAP with default-ip will reboot automatically for IP recovery.
     
  • Master (without 3G dongle) is UP for less than 5 mins, then a new IAP (with 3G dongle) comes up. The new IAP becomes the new Master.

NOTE: IAP Master Election Process, do not take InstantOS in to consideration. After the Master is elected, the virtual controller can take of image synhcronization with slave IAP's.

 

Comments
jhonnyR

Hello guys,

 

This beacon works in the wired site?

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