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Listening to 802.11N Wi-Fi traffic with tcpdump

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http://forums.fedoraforum.org – I want to diagnose some problems on my Wi-Fi network. I would like to capture the communication between an 802.11N client and an 802.11N access point. I have a lenovo ThinkPad T61p laptop with an IWL4965N chipset that runs Fedora 11 and that I want to use as a monitoring device. I can connect to the 802.11N access point with the lenovo laptop and get to the Internet. My expectation is that it can also monitor 802.11N traffic. However, if I perform a tcpdump on the Wi-Fi interface, I only see a few packets exchanged between the client and the AP (all are broadcast packets on port 137 and sometimes an ARP broadcast). Even though I am stgreaming some traffic on the client, I can't see that traffic for some reason. If I connect my client to another access point on a G-channel instead of an N-channel, I can see all its traffic with tcpdump. I am wondering why I can't see N-channel end-user traffic using tcpdump on my Fedora system. Is there an explanation. I am using kernel 2.6.30.8-64.fc11.i586 Martin (HowTos)