Setting up Cisco Access Points (APs)
When using a Cisco lightweight Access Point (AP), you need to set up the Cisco Wireless LAN Controller (WLC) to accept registration of APs. This set up is all part of the controller discovery process.
Cisco’s lightweight access points (LWAPs) use the Lightweight Access Point Protocol (LWAPP) to communicate between the components of the wireless network infrastructure. In this environment, your access point needs to be associated or linked with a controller to properly function.
The discovery process is the system that allows this association to occur. After an access point is associated with a WLC, its full potential can be reached.
The LWAP sends a join request to the controller.
The controller acknowledges this request by sending a join response to the lightweight access point.
The LWAP has permission to become associated with the controller and stores the controller connection information locally.
After the discovery process is complete, the controller can manage all aspects of the lightweight access point, such as its configuration, firmware, control transactions, and data transactions.
Methods for discovering an AP
A lightweight access point can be discovered in the following ways:
Layer 3 LWAPP discovery: This discovery occurs when the LWAP is on a different subnet from the WLC and the AP uses the IP address rather than the Layer 2 MAC address.
Layer 2 LWAPP discovery: This discovery occurs when the LWAP and WLC are on the same subnet and the discovery data is placed in Ethernet frames that contain the MAC addresses of the two devices.
Layer 2 LWAPP discovery cannot be used in Layer 3 environments.
Over-the-air provisioning (OTAP): This option is supported only by Cisco 5500, Cisco 4400, and Cisco 2100 series WLCs. If the option is enabled, all associated access points send neighbor messages. These neighbor messages allow new LWAP devices to receive the WLC’s IP address, where they can conduct the rest of the discovery process. After this process has been completed, the option on the controller should be disabled.
Locally stored controller IP address discovery: After a discovery has been completed, the AP stores the addresses for its controllers in nonvolatile memory so that, for later deployment, it has all the necessary controller information. This process is called priming the access point.
DHCP server discovery: This option allows the DHCP option 43 to provide controller IP addresses to the access points.
DNS discovery: Domain Name System (DNS) information for the controller can be stored in your DNS zone. The record should be called CISCO-LWAPP-CONTROLLER.localdomain, where localdomain is the access point domain name. After the AP knows the IP address of the controller, it can connect to the controller to complete the registration process.
Locating a specific LWAP
From time to time, you may need to locate a specific lightweight access point on your network. The easiest way to do this is to configure the access point to flash its LEDs. This feature is supported on any controller software release 4.0 or later and all lightweight access points. To flash an access point’s LEDs, issue the following command:
debug ap enable Cisco_AP
To cause a specific access point to flash its LEDs for a specified number of seconds, issue this command:
debug ap command "led flash seconds" Cisco_AP
You can enter a value between 1 and 3600 for the seconds parameter. To disable LED flashing for a specific access point, use the following command:
debug ap command "led flash disable" Cisco_AP