backup different WLCs with a unique WLC hosted in a central site

Unanswered Question
May 28th, 2009

Hi everybody, I'm trying to understand if there's a way to backup different WLC (in different remote sites) with a unique WLC hosted in a central site. This is an sample scenario, best explained. I have 3 remote sites, each of them with an amount of LAP (say 60 LAP) and with its own WLC. LAPs are normally registered to their local WLC and everything is fine. One local WLC dies: is there a way to use the WLC hosted in the central site to backup the WLC that has come to death? If yes, how can the backup WLC understand which is the remote dead WLC and load the exact configuration?

Please help!


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Overall Rating: 3.7 (3 ratings)
Leo Laohoo Thu, 05/28/2009 - 21:36

One method of allowing the AP's to Join another WLC when in failure is to use the "High Availability" feature. This can sometime be called Primary/Secondary/Tertiary Controller.

Depending on the firmware you are using, you can configure the AP Primary/Secondary/Tertiary Controller. So if WLC 1 dies, AP's initially joined to WLC 1 can join WLC 2 or WLC 3.

Does this answer your question?

Leo Laohoo Thu, 05/28/2009 - 21:38

Another option is to configure H-REAP. When H-REAP is enabled, when the WLC 1 dies, the AP's initially joined to to WLC 1 will operate "normally", unless you reboot the AP's. It will only search for WLC 2 or WLC 3 if the AP's are rebooted.

tecnotelsrl Fri, 05/29/2009 - 01:33

Thank you leolaohoo, your answers are really useful but leave some of my doubts...

The scenario is the following: I have one central site and many remote sites. Remote sites are equipped with a large amount of AP, from 50 to 100 for each site: the logical solution is to provide a WLC for each remote site; thus, in normal situation, all APs in a remote site will be joined to their local WLC.

The backup architecture I'm focusing on is the following: can I install a WLC in central site (no APs will be present in central site) and use it as a backup/secondary WLC in case of a remote site WLC failure? I'd like that the normally “sleeping” WLC installed in central site could “take the place” of one of the WLC installed in remote sites, the one which fails. My doubt is: how can the backup WLC understand which is the failed WLC and take the exact configuration? Is there a way to do that? Or something similar?


Leo Laohoo Sat, 05/30/2009 - 21:31

Can I install a WLC in central site (no APs will be present in central site) and use it as a backup/secondary WLC in case of a remote site WLC failure?

You sure can. In each of the WLC, you need to configure the Secondary and/or Tertiary Controllers. This way, when the primary fails, the AP's can immediately to go the Secondary and/or Tertiary Controllers for their configs.

In my previous job, we had four controllers found in three different states. Secondary and/or Tertiary Controllers, when one of the controllers failed, each of the AP's went to Secondary Controllers immediately.

The main point to consider is that each networks are similar if not the same. The only thing that is different from each of them are the sites' IP Addresses.

Hope this helps.

tecnotelsrl Tue, 06/02/2009 - 07:25

Sure, this help, thaks a lot. What happens if the configuration in different sites is different? Different number of AP, different WLAN/VLAN mapping? Thanks a lot

John.Gerlach Tue, 06/02/2009 - 08:29

If your controllers are part of the same mobility Domain you can make use of the AP Groups feature (WLANS|Advanced|AP Groups) and use the same AP Group names on both your Primary and Backup controllers. Be aware that there is overhead to consider with your controllers being on the same mobility group (client information is continually exchanged in order to be prepared for a client roam).

On your backup controller you would need likely need to create interfaces with different addresses. But then you can create all of the WLANs you need and associate them to the defined interfaces. Keeping in mind that a change in scope for the IP addresses of the various WLANs and that the role of this unit is as a backup you may be able to minimize some work and use the same interfaces for all sites but that is a personal decision (maybe you like a lot of work).

Then you can create each AP Group you need and add the required WLAN support into each one.

Or you could just create a generic default-group policy that is applied to ride you through your outage.


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