802.11 frame translation :- WLC or AP or Both ?

Unanswered Question
Apr 11th, 2010


In an LWAPP environment, who does the 802.3 to 802.11 frame translation ?

I thought it was the WLC alone that did it.

However, in the Cisco Press book, "Deploying and Troubleshooting Cisco Wireless Lan Controllers", it seems to suggest,

that when frames are sent to the wired network, the WLC does the bridging, and when they are sent back to the wireless network,

the AP does it.

Can someone please clarify ?


I have this problem too.
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dancampb Mon, 04/12/2010 - 06:40

The 802.3 mac headers are stripped at the controller and the 802.11 header is added.  Then the entire frame has a CAPWAP or LWAPP headder, new IP header, and new mac header added on top of the 802.11 header.  The now encapsulated packet is sent out of the controller to the AP where the mac, outter IP, and CAPWAP/LWAPP header is removed and the 802.11 packet is transmitted out the AP.  So the conversion from an 802.3 to 802.11 packet happens at the controller but there is a new 802.3 header applied so the packet can be sent over the wire between the AP and controller.

smvoicerite Mon, 04/12/2010 - 20:05

Thanks Dan.

And I assume that the same is true (i.e controller translating the frame from 802.11 to 802.3), when its from the wireless to DS.

Thats what I thought as well, so it must be an error in the book.

Also, I found a setting in the WLC, under Controller -> General, which is a flag, 802.3 bridiging (true/false). Any idea what this might be ?



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