99.99.0/24CORPORATE USERMAC

10.99.99.0/24Corporate UserMAC: 0000.0001.0001

Figure 9-5 ARP Forwarded in LWAPP Frame

The LWAPP frame that travels from the AP to the WLC is traveling on a wired network.

This brings forth the question, “What happened to the 802.11 frame format?” LWAPP

simply encapsulates the frame inside a 6-byte header. The new 6-byte header has the AP

IP and MAC address as the source and the WLC IP and MAC address as the destination.

Encapsulated inside of that header is the original 802.11 frame with the three MAC ad-

dresses, including the broadcast MAC address for the ARP process. When the WLC re-

ceives the LWAPP frame, it opens the frame revealing the ARP request and rewrites the

ARP request in an 802.3 frame that can be sent across the wired network. The first ad-

dress from the 802.11 frame is dropped, the second address is placed as the source address

in the new 802.3 frame, and the third address, the broadcast address, is placed as the desti-

nation address. The WLC then forwards the ARP request, in 802.3 format, across the

wired network, as seen in Figure 9-6. Here you can see how the frame appears between

the wireless Client A and the AP, how the AP encapsulates the frame and sends it to the

WLC, and how the WLC rewrites the frame and sends it to the wired network.

GatewayKey TopicUUARPController toSOURCEDESTINATION