Gaining AP capacity with secondary 5508 wireless controller

[Steven Shelton]

My customer has three 5508 controllers but only one in production which is licensed for 500 APs.  Upcoming wireless expansion will exceed the 500 AP limit on the current production WLC.  First question, can someone point to the documentation regarding using multiple 5508 WLCs for capacity or explain the configuration requirements.  Secondly, assuming the second controller is in production, is it possible for the third WLC to be a backup controller for the two production controllers?

Thank you

[Scott Fella]

You first need to determine if all WLC's have licenses or not. This is a requirement for access points to join. So in your case, I'm assuming you don't have any HA Sku WLC's and all controllers will have licenses.  Here is a link in how to define what the primary, secondary or tertiary WLC for a given access point is. 

http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/69639-wlc-failover.html

-Scott

[Steven Shelton]

Thank you for the link.  As part of the expansion project, additional AP licensing would be purchased along with the APs.  Is it correct to say if the customer remains on the 5508 platform and their total AP count is >500, then a HA design would not be possible?

[Scott Fella]

There are various ways to achieve HA.  What I would do in your case is maybe have two WLC's with 500 AP license or just enough for the access points you need. These will be considered primary for those access points. Then the 3rd WLC you only need a 50 license and then set that up as HA N+1 and this will be he backup for up to 500 access points. Now even though this has a 50 license, with v7.4 code, you are allowed to set this up as a backup.  

Here is a link describing HA N+1:

http://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide.pdf

-Scott

[Steven Shelton]

The HA N+1 design is definitely the desired architecture.  Looking at the HA docs previously, I wasn't sure it would work in a design with 750 APs and two 5508 WLCs.  

Thanks, I'll take another look at the HA Doc.

[Scott Fella]

You will not be able to support both primary controllers failing if it does happen, since the backup will only support 500 max. 

-Scott