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Community Manager

Malformed radiotap header and missing SNR - Intel Centrino Ultimate -N 6300

I have set up an experiment to measure Wireless communication parameters using two laptops. I am injecting custom packets into the network on a monitor interface using one laptop programmed as a transmitter(Macbook Pro using Broadcom BCM 4331 interface card) and another laptop ( Dell Latitude E6410 using the Intel Corporation Centrino Ultimate-N 6300 interface card) programmed as a receiver sniffs the network for the custom injected packets and reports parameters such as Received signal strength, propagation delay etc... The transmission is working fine and i am able to get the injected packets on the receiving side.

However , When i use Wireshark to analyze the incoming packets using the monitor interface created using airmon-ng, the radio tap header seems to be malformed. This is the same for all packets .

Also why is the Noise parameter now shown in the radio tap details?

Could anyone help me out with this?

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Community Manager

Hello Anand, thank you for your post. The issue is that these adapters are designed to not support Promiscuous mode therefore getting strange results would be or while doing packet analysis would be expected.


We are sorry for any inconveniences this may cause.

Community Manager

Hi Nathalie,

Thanks for the reply. The packet as reported by Wireshark appears to be fine except that it shows "Malformed" in the title. The payload details seem to be spot on. But however i do not have access to the background noise value.

The same problem exists in iwconfig. The Noise level is not shown.

mon0 IEEE 802.11abgn Mode:Monitor Tx-Power=15 dBm


Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off

wlan0 IEEE 802.11abgn ESSID:"AirPennNet"


Mode:Managed Frequency:2.412 GHz Access Point: D8:C7:C8:D7:A6:C1


Bit Rate=130 Mb/s Tx-Power=15 dBm


Retry long limit:7 RTS thr:off Fragment thr:off Power Management:on Link Quality=65/70 Signal level=-45 dBm


Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:800 Invalid misc:540 Missed beacon:0

eth0 no wireless extensions.

I tried to use cat /proc/net/wireless and got these results

Inter-| sta-| Quality | Discarded packets | Missed | WE face | tus | link level noise | nwid crypt frag retry misc | beacon | 22 wlan0: 0000 64. -46. -256 0 0 0 818 566 0

Is -256 the noise level? Surely, the noise value cannot be 0 dBm.

I understand the Noise level as reported by the wireless interface card may not be made available to userspace. Is there another way i can access this value? I need to analyze it for my research project. Would it be possible for you to give me a patched driver or something like that?

Sorry for the trouble.