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
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