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Cisco Wireless LAN Controller Configuration Guide
OL-9141-03
Chapter 7 Controlling Lightweight Access Points
The Controller Discovery Process
The Controller Discovery Process
Cisco’s lightweight access points use the Lightweight Access Point Protocol (LWAPP) to communicate
between the controller and other lightweight access points on the network. In an LWAPP environment,
a lightweight access point discovers a controller by using LWAPP discovery mechanisms and then sends
it an LWAPP join request. The controller sends the access point an LWAPP join response allowing the
access point to join the controller. When the access point joins the controller, the controller manages its
configuration, firmware, control transactions, and data transactions.
Note
You must install software release 4.0.155.0 or greater on the controller before connecting 1100 and 1300
series access points to the controller. The 1120 and 1310 access points were not supported prior to
software release 4.0.155.0.
Note
The Cisco controllers cannot edit or query any access point information using the CLI if the name of the
access point contains a space.
Lightweight access points must be discovered by a controller before they can become an active part of
the network. The lightweight access points support these controller discovery processes:
•
Layer 3 LWAPP discovery
—Can occur on different subnets from the access point and uses IP
addresses and UDP packets rather the MAC addresses used by Layer 2 discovery.
•
Layer 2 LWAPP discovery
—Occurs on the same subnet as the access point and uses encapsulated
Ethernet frames containing MAC addresses for communications between the access point and the
controller. Layer 2 LWAPP discovery is not suited for Layer 3 environments.
•
Over-the-air provisioning (OTAP)
—This feature is supported by Cisco 4400 series controllers. If
this feature is enabled on the controller, all associated access points transmit wireless LWAPP
neighbor messages, and new access points receive the controller IP address from these messages.
This feature should be disabled when all access points are installed.
•
Locally stored controller IP address discovery
—If the access point was previously associated to
a controller, the IP addresses of the primary, secondary, and tertiary controllers are stored in the
access point’s non-volatile memory. This process of storing controller IP addresses on access points
for later deployment is called
priming the access point
.
•
DHCP server discovery
—This feature uses DHCP option 43 to provide controller IP addresses to
the access points. Cisco switches support a DHCP server option that is typically used for this
capability. For more information about DHCP option 43, see the
“Using DHCP Option 43” section
on page 7-22
.
•
DNS discovery
—The access point can discover controllers through your domain name server
(DNS). For the access point to do so, you must configure your DNS to return controller IP addresses
in response to CISCO-LWAPP-CONTROLLER.
localdomain
, where
localdomain
is the access point
domain name. When an access point receives an IP address and DNS information from a DHCP
server, it contacts the DNS to resolve CISCO-LWAPP-CONTROLLER@
localdomain
. When the
DNS sends a list of controller IP addresses, the access point sends discovery requests to the
controllers.
