Controllerless Networks

Have the new 802.11ac IAPs been integrated into the master election hierarchy? If so is there any information available?

Thanks, Johnny.

as far as I know regardless of the type of AP as long as it is instant, it will follow the same rules for master election hierarchy.

If you have a mixed mode environment, like let's say a 225 and a 105, the 225 will take precedence over the 105 and become master

The election process is as follows below.  You can also set a preferred master.

 

The first IAP to boot is the default VC.    If it fails, the election process uses the following conditions to choose the new VC.

 

1. An IAP with an alternative uplink (3G or 4G only) receives preference.
2. If an IAP with an alternative uplink is not available, an IAP with the most capable hardware receives preference in the following descending order: [IAP225] > [IAP134/5 = RAP155] > [IAP104/5 = IAP175 = RAP108/9 = RAP3] > [IAP92/3]
3. If both of the previous considerations are not applicable, an IAP with the longest uptime receives preference.

If an IAP with one of the above joins a cluster and "outranks" the existing VC, it does NOT take over; the process only occurs on a failure of the VC.

 

 

EDIT:

on #2 above, I would assume the IAP-215 and IAP-205 would fall between the IAP-225 and IAP-13x.

Ok, so the 220 series is above the 130 in the hierarchy now - that's what I needed to know.

Thanks.

Yes it is; but again, only on a failure.   If an IAP135 is the first one up, then it will assume and keep the VC role until failure/reboot.

There are only two IAP models that make use of the HW Priortiy -- IAP-13x and RAP-155.  The HW priority comes near the end of the pecking order in the election process so even if you have an IAP-13x or RAP-155 in the network there is no guarantee that it will become the Master.

 

When you you reboot an entire swarm (with 105, 135, 225, etc), there is no guarantee that 135 will become the master as this depends on following factors:

1. Actual booting time is different for each AP model;
2. Due to switch behavior, when to unblock a port is hard to decide;
3. Each IAP has a random backoff before election

The only way to guarantee that a specific IAP becomes the Master is to use the "Preferred Master" option.

#RAP155