Configuring the backup controller

Unanswered Question
Apr 2nd, 2008


I am trying to get some clarity on how the backup controllers work. here is a scenario 2 controllers one in Site A and one in Site B. The APs in Site B have SSID tsunami-123 are mapped to VLAN 45. If the Site B controller went down and their backup controller is in Site A what do I have to have on the backup controller to support the Site B APs? Do I have to have the same VLAN # and the same SSID on the backup controller? What i am trying to understand is how to configure the backup controller to be able to support the users that will now be on the Site A controller.

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Scott Fella Wed, 04/02/2008 - 13:59

All you need is the ssid, so the users will not have to be reconfigured. The traffic will folw back to Site A to what ever vlan you mapped the ssid to. Make sure the subnet is large enough for failover... if you have 200 devices on each site, you will need enough dhcp adddress for 400 devices. You can't have static ip address on the client since you can't have the same subnet on both Sites. Hope this helps.

imuratov Wed, 04/02/2008 - 14:09

So what if the APs in the Site B be setup as H-REAP APs even though the controller is local. Once the controller in Site B fails the APs will now switch over to Site A controller and switch traffic locally. Would this work? The reason i am asking is that both site are big and have 4404-100 and i am maxing each controller not to have more than 50 APs connect to them. so in the event of failure they can back each other up. Both site connect to each other through DS3.

Scott Fella Wed, 04/02/2008 - 15:06

If you use H-REAP all you need to do is make sure the SSID are configured on both controllers. Also if you use AP Groups or WLAN Override. Once the AP fials to a different controller, it get the general info from that controller. the only settings that the AP keeps is what you configure on the AP itself.

imuratov Thu, 04/03/2008 - 06:51

Are there any issues on doing this type of setup? What will I loose in return? Would roaming be affected?

Scott Fella Thu, 04/03/2008 - 18:17

There is no roaming issues since the traffic will be local. In h-reap, the ap's can loose connection to the WLC and users will still have network connectivity. Only if you are using central authentication will you have issues if the ap looses connection to the wlc. If you don't have the bandwidth to keep the ap's on local mode then h-reap is your only choice.

ahmedalshami Sun, 04/06/2008 - 00:50

All what you need is configure the same SSID in the secondary controller then make group domain (same group name in both Controller)

From Wireless tab in controller click on the Access points configure and put the primary name for Controller in primary

And the secondary name in the secondary

Try to ping the first controller from secondary if ok do failover test

Good luck


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