The following will provide some 802.11 network details, and will describe how to disable the translation/filtering and see what's "really" going on inside your WLAN. That's one of the reasons why the 802.11 network adapters have two additional mechanisms to ignore unwanted packets at the receiving side: channels and SSID's.Ĭonclusion: the packets you'll be capturing with default settings might be modified, and only a limited number of the packets transmitted through the WLAN. Compared to Ethernet, the 802.11 network is even "broader", as the transmitted packets are not limited by the cable medium. In this case, you won't see any 802.11 management or control packets at all, and the 802.11 packet headers are "translated" by the network driver to "fake" Ethernet packet headers.Ī 802.11 LAN uses a "broadcast medium", much like (the mostly obsolete shared) Ethernet. Without any interaction, capturing on WLAN's may capture only user data packets with "fake" Ethernet headers. traffic between two or more other machines on an Ethernet segment, or are interested in 802.11 management or control packets, or are interested in radio-layer information about packets, you will probably have to capture in "monitor mode". If you're trying to capture network traffic that's not being sent to or from the machine running Wireshark or TShark, i.e. network traffic from that machine to itself, you will need to capture on a loopback interface, if that's possible see CaptureSetup/Loopback.) (If you're trying to capture network traffic between processes running on the machine running Wireshark or TShark, i.e. If you are only trying to capture network traffic between the machine running Wireshark or TShark and other machines on the network, are only interested in regular network data, rather than 802.11 management or control packets, and are not interested in radio-layer information about packets such as signal strength and data rates, you should be able to do this by capturing on the network interface through which the packets will be transmitted and received no special setup should be necessary. Use promiscous mode only as backup.įurthermore, some wirelesse driver/hardware allows your device to send completely arbitrary packets while in monitor mode - this is called packet injection.The following will explain capturing on 802.11 wireless networks ( WLAN). If the tool you want to use supports monitor mode, use it. So monitor mode is advantageous if you want to really see what's going on, while promiscous mode is there for compatibility with standard ethernet network sniffing tools that can't handle the extended 802.11 frame format. Only special wireless monitoring software is able to process packets in the format dumped by the driver in monitor mode. In "monitor mode", you capture packets from all the networks operating on a chosen channel (possibly even adjacent channels - there is a reason that 802.11 DSSS beacons contain the channel number in the payload), and the driver does not output plain ethernet, but needs to output more headers (there are 3 addresses in a 802.11 header, instead of just 2 addresses in the 802.3 ethernet headers). Possibly the device will only dump packets from the AP to wireless devices, but not packets from wireless clients to the AP, as receiving packets from non-AP devices is not used in AP client mode. In "Promiscous mode", the driver still outputs standard ethernet frames belonging to the one wireless network you are currently associated to (identified by the BSSID).
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