High Availability Enhancements

Answered Question

I have two 5508 WLC v7.0. Two locations.  Assigning Primary and secondary controllers to the APs how long would a client be "down" if a controller failed (assuming all APs are on one WLC)

Would the type of wireless security be a consideration for speed of recovery?( PEAP , EAP-FAST)

Would running HREAP help, knowing the clients are considered down if they cannot reach services not on the local network.

What would be some "Best Practices" to use? We are looking for the quickest fail over time.

My first thought was to have "every other AP" assigned to different controllers. so the clients had a 50% chance of being on the controller that did not fail.

I have this problem too.
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Correct Answer by Leo Laohoo about 6 years 4 months ago

So if a controller fails there is a 5-15 second period of time the cleints will be "down" then the new controller takes over.

If my memory on the time for the AP to search for another controller is correct, yes.  The client will be down.  You can also speed up failover using the "priority" option.  Default is set to "Low".

With HREAP will the clients, while the controllers are swapping, be able to access outside traffic as they were before the controller died?

With H-REAP enabled, when the AP searches for the controller, all traffic will be pushed into the local LAN.  Basically, I've tried using a single controller and enabled H-REAP.  I turned OFF the WLC for an entire week and we were able to do wireless (including voice).  Just make sure that when this happens, DO NOT reboot your AP.

Hope this helps.  Please don't forget to rate useful posts.

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Leo Laohoo Sun, 08/08/2010 - 15:29

About 5-15 seconds, I think.  If you want "seamless" transitions without any client disruptions consider enabling H-REAP.

Correct Answer
Leo Laohoo Tue, 08/10/2010 - 14:37

So if a controller fails there is a 5-15 second period of time the cleints will be "down" then the new controller takes over.

If my memory on the time for the AP to search for another controller is correct, yes.  The client will be down.  You can also speed up failover using the "priority" option.  Default is set to "Low".

With HREAP will the clients, while the controllers are swapping, be able to access outside traffic as they were before the controller died?

With H-REAP enabled, when the AP searches for the controller, all traffic will be pushed into the local LAN.  Basically, I've tried using a single controller and enabled H-REAP.  I turned OFF the WLC for an entire week and we were able to do wireless (including voice).  Just make sure that when this happens, DO NOT reboot your AP.

Hope this helps.  Please don't forget to rate useful posts.

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