The Wireless LAN Controller (WLC) acts as a Dynamic Host Configuration Protocol (DHCP) relay device. The WLC does the DHCP relay through the virtual interface. Typically, the 184.108.40.206 address is assigned to the virtual interface. This address can be any address. However, it must not be a routable address.
This is the sequence of events that occur:
The WLAN client sees the administration-defined virtual address as the DHCP server address. The recommended address is usually 220.127.116.11 because this address is not normally a routable network address.
The WLC shows the virtual address to the WLAN clients and the management interface address upstream.
The WLC acts as a DHCP relay (Bootstrap Protocol [BOOTP] relay) device.
Note: When the internal DHCP server is used, the lightweight access point (LAP) must be directly connected to the WLC. Also, a DHCP scope cannot be shared between two or more WLCs.
Note: If you run a DHCP server on a PIX 501, the PIX does not support DHCP requests from a relay agent, which is how the WLC sends the request. You also need to configure a DHCP scope internal to the controller and remove DHCP override from the WLAN.