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Pre-staging Lightweight APs for Specific Controllers on a Production Network
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Q:
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I’m having problems getting lightweight Cisco APs to associate with specific controllers on my network. I have multiple controllers on a flat subnet and the APs keep associating with the wrong controller. Is there anything I can do to ensure that APs “settle” to specific controller on my production network?
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A:
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Cisco provides several convenient options to get lightweight access points (APs) to “settle” on a particular controller on a production network:
>> Subnet broadcasts
>> DHCP, option 43
>> DNS resolution of the name CISCO-LWAPP-CONTROLLER
>> Configuration of a Master Controller
Each method is convenient, but sometimes conflicting. In a network that has multiple controllers on one flat subnet, APs can be very stubborn about which controller to associate with. So, the best way to get APs to connect to a particular controller is to pre-stage them from a controlled, laboratory-type network.
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Steps to pre-stage a controller:
Follow these easy steps to create a Controller Template that will “push” a new local user name and password onto your Wireless LAN Controller (WLC). Please note the following before proceeding: The Wireless LAN Controller in question must be added to the Wireless Control System (WCS) before you can successfully complete the process.
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1.
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Set up a lab network. This network should have a single controller giving APs only one choice. This can be accomplished in three separate methods: randomly choose a controller to become the Master Controller, choose to set the DHCP option 43 or create a hostname record on the DNS server that is set to CISCO-LWAPP-CONTROLLER. Only one method is needed to be certain that with only one controller on the network, the AP will connect to it through the discovery process.
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2.
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Important: Be certain that the controller on the lab network is given a name that is not used anywhere on the production network. The AP will remember the last controller name it received a configuration from. If the AP can’t find the named controller, it will look for another controller in which to connect.
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3.
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When the AP appears on the lab network and associates to the lab controller, configure it for a primary and secondary controller with names that are on the production network. Because there are certain things a lightweight AP will remember after it reboots, it will remember its IP address (if static), hostname, whether or not 802.11h detected radar on a supported 5 GHz channel, the hostname of the last controller that gave it a configuration, and the primary and secondary controllers it was configured with in the lab network. The fact that those controllers can not be reached from the lab network is immaterial.
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4.
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Be certain AP Fallback is enabled on the network. This is accomplished by going to Controller>General and enabling AP Fallback. AP Fallback guarantees that APs will return to their Primary Controllers whenever possible. This process can take a few minutes to complete.
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5.
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Move the AP to the production network.
>> The AP will first try to find the controller that last configured it. This will fail because that controller does not exist on this network.
>> The AP will then try to find its primary controller. If the AP is on the production network, this should succeed.
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To learn more, contact GigaWave Technologies at 210.375.0085 or info@giga-wave.com
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