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> Chapter 12 - FortiWiFi and FortiAP Configuration Guide > Access point deployment > Advanced WiFi controller discovery

Advanced WiFi controller discovery

A FortiAP unit can use any of six methods to locate a controller. By default, FortiAP units cycle through all six of the discovery methods. In most cases there is no need to make configuration changes on the FortiAP unit.

There are exceptions. The following section describes the WiFi controller discovery methods in more detail and provides information about configuration changes you might need to make so that discovery will work.

Controller discovery methods

There are six methods that a FortiAP unit can use to discover a WiFi controller. Below is the list of AC discovery methods used in sequence:

0(auto) → 1(static) → 2(dhcp) → 3(dns) → 7(forticloud) → 5(broadcast) → 6(multicast)

Static IP configuration

If FortiAP and the controller are not in the same subnet, broadcast and multicast packets cannot reach the controller. The admin can specify the controller’s static IP on the AP unit. The AP unit sends a discovery request message in unicast to the controller. Routing must be properly configured in both directions.

To specify the controller’s IP address on a FortiAP unit

cfg –a AC_IPADDR_1=""


By default, the FortiAP unit receives its IP address, netmask, and gateway address by DHCP. If you prefer, you can assign these statically.

To assign a static IP address to the FortiAP unit


cfg –a AP_IPADDR=""

cfg -a AP_NETMASK=""

cfg –a IPGW=

cfg -c


For information about connecting to the FortiAP CLI, see Connecting to the FortiAP CLI.


If you use DHCP to assign an IP address to your FortiAP unit, you can also provide the WiFi controller IP address at the same time. This is useful if the AP is located remotely from the WiFi controller and other discovery techniques will not work.

When you configure the DHCP server, configure Option 138 to specify the WiFi controller IP address. You need to convert the address into hexadecimal. Convert each octet value separately from left to right and concatenate them. For example, converts to C0A80001.

If Option 138 is used for some other purpose on your network, you can use a different option number if you configure the AP units to match.

To change the FortiAP DHCP option code

To use option code 139 for example, enter



For information about connecting to the FortiAP CLI, see Advanced WiFi controller 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. Allow DNS lookup of the hostname configured in the AP by using the AP parameter "AC_HOSTNAME_1".


The access point can discover FortiCloud by doing a DNS lookup of the hardcoded FortiCloud AP controller hostname "". The forticloud AC discovery technique finds the AC info from using HTTPS.

FortiCloud APController:

Broadcast request

The AP unit broadcasts a discovery request message to the network and the controller replies. The AP and the controller must be in the same broadcast domain. No configuration adjustments are required.

Multicast request

The AP unit sends a multicast discovery request and the controller replies with a unicast discovery response message. The AP and the controller do not need to be in the same broadcast domain if multicast routing is properly configured.

The default multicast destination address is It can be changed through the CLI. The address must be same on the controller and AP.

To change the multicast address on the controller

config wireless-controller global

set discovery-mc-addr


To change the multicast address on a FortiAP unit



For information about connecting to the FortiAP CLI, see Advanced WiFi controller discovery.