Wireless Controller
Dedicated Wi-Fi control and management for high density and mobility
nmichael
Staff
Staff
Article Id 192148
Description

How does AP discovery work?


Scope

KB ARTICLE TYPE:Design

RELATED PRODUCTS: Applies to all

RELATED SOFTWARE VERSIONS: Applies to all

KEYWORDS: AP, Discovery


Solution
There are three types of access point discovery

1 - Layer 2 only—Access point is in same subnet as controller.

2 - Layer 2 preferred—Access point sends broadcasts to find the controller by trying Layer 2 discovery first. If the access point gets no response, it tries Layer 3 discovery.

3 - Layer 3 preferred—Access point send broadcasts to find the controller by trying Layer 3 discovery first. If the access point gets no response, it tries Layer 2 discovery.For Layer 2 and Layer 3 discovery, the access point cycles between Layer 2 and Layer3 until it finds the controller.

The access point waits 16 seconds before cycling between Layer 2 and Layer 3.

An access point obtains its own IP address from DHCP (the default method), or you can assign a static IP address. After the access point has an IP address, it must find a controller’s IP address. By default, when using Layer 3 discovery, the access point obtains the controller’s IP address by using DNS and querying for hostname “wlan-controller.


” This presumes the DNS server knows the domain name where the controller is located.   The domain name can be entered via the AP configuration or it can be obtained from the DHCP server, but without it, an Layer 3-configured AP will fail to find a controller.

Alternately, you can configure the AP to point to the controller's IP directly  (if the controller has a static IP configuration).After the access point obtains  the controller IP address, it sends broadcast messages using UDP port 9393.

After the controller acknowledges the messages, a link is formed between the AP  and the controller.


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