When Cisco's Wireless Unified Architecture is deployed, the Cisco
Aironet Lightweight Access Points (LAPs) can discover wireless LAN controllers
(WLCs) using the DNS server when the WLC is in a different subnet than the LAP.
This document describes how to configure the Microsoft Windows 2003 DNS
server for WLC discovery.
Cisco recommends that you have knowledge of these topics:
This document is not restricted to specific software and hardware
The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.
Technical Tips Conventions for more information on document
The LAP can discover controllers through your domain name server (DNS).
For the access point (AP) to do so, you must configure your DNS to return
controller IP addresses in response to
CISCO-LWAPP-CONTROLLER.localdomain, where localdomain is the
AP domain name. When an AP 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 AP sends discovery requests to the
The AP will attempt to resolve the DNS name
CISCO-LWAPP-CONTROLLER.localdomain. When the AP is able to
resolve this name to one or more IP addresses, the AP sends a unicast LWAPP
Discovery Message to the resolved IP address(es). Each WLC that receives the
LWAPP Discovery Request Message replies with a unicast LWAPP Discovery Response
to the AP.
The next section describes how to configure the Microsoft Windows 2003
server for WLC discovery.
Complete these steps in order to configure the Microsoft Windows 2003
DNS server for WLC discovery:
Click Start -> Run.
Enter the mmc command and click
The Microsoft Management Console window appears.
From the File menu, choose Add-Remove
In the Add/ Remove Snap-in window, select the
Standalone tab and click Add.
From the Add Standalone Snap-in window, choose DNS
and click Add. Then click Close to return to
the Add/ Remove Snap-in window. Click
DNS now appears in the MMC window.
Expand the + sign to see your Domain
Expand the + next to the Domain Controller to see
the Event Viewer, Forward Lookup Zones, and Reverse Lookup Zones that are
Expand the + next to Forward Lookup
You will see your domains listed. This example shows
Choose the domain and right-click. Click New Host
A new window appears.
Enter CISCO-LWAPP-CONTROLLER in the name field.
Enter your controllers Management Inteface IP address, then
click Add Host.
This way the DNS server has mapped the
CISCO-LWAPP-CONTROLLER hostname to the IP address of the
controller management interface. Now when the LAP boots and performs the
controller discovery, the AP will attempt to resolve the DNS name
CISCO-LWAPP-CONTROLLER.localdomain. Once it knows the
management IP address of the WLC, it sends a unicast LWAPP Discovery Request
Message to the controller and the controller responds with a discovery
After this is done, join process begins. For complete information
on the LWAPP discovery and join process, refer to
AP (LAP) Registration to a Wireless LAN Controller (WLC).
The AP looks up CISCO-LWAPP-CONTROLLER.cisco.com if no DNS
suffix is supplied to the AP from the DHCP server.
This is a known issue. An LWAPP IOS AP, when it boots up, attempts to
resolve the CISCO-LWAPP-CONTROLLER domain name.
First, it will attempt to resolve
Then, it will attempt to resolve
This occurs when the AP has not been configured with a default domain
suffix (for example, from the DHCP server). In order to resolve this issue,
configure the AP's DHCP server to supply it with a default domain suffix.