O modo Promiscious nem sempre permite que você veja o tráfego enquanto o isolamento do Cliente está em jogo. O modo promíscuo significa apenas que o seu PC processará todos os quadros recebidos e decodificados. Em muitos APs / wnics / oses, o modo promíscuo não verá tráfego para outros sistemas.
Na documentação do Wireshark:
Monitor mode
In monitor mode the SSID filter mentioned above is disabled and all packets of all SSID's from the currently selected channel are captured.
Even in promiscuous mode, an 802.11 adapter will only supply to the host packets of the SSID the adapter has joined, assuming promiscuous mode works at all; even if it "works", it might only supply to the host the same packets that would be seen in non-promiscuous mode. Although it can receive, at the radio level, packets on other SSID's, it will not forward them to the host.
Monitor Mode (que eu acredito que é o que você quer) irá capturar todo o tráfego do SSID, e outros SSIDs em alcance.
A documentação do Wireshark continua:
Therefore, in order to capture all traffic that the adapter can receive, the adapter must be put into "monitor mode", sometimes called "rfmon mode". In this mode, the driver will put the adapter in a mode where it will supply to the host packets from all service sets. Depending on the adapter and the driver, this might disassociate the adapter from the SSID, so that the machine will not be able to use that adapter for network traffic, or it might leave the adapter associated, so that it can still be used for network traffic. If it disassociates the adapter from the SSID, and the host doesn't have any other network adapters, it will not be able to:
* resolve addresses to host names using a network protocol such as DNS; * save packets to a file on a network file server; * etc..
Monitor mode is not supported by WinPcap, and thus not by Wireshark or TShark, on Windows. It is supported, for at least some interfaces, on some versions of Linux, FreeBSD, NetBSD, OpenBSD, DragonFly BSD, and Mac OS X.
You might have to perform operating-system-dependent and adapter-type-dependent operations to enable monitor mode, described below in the "Turning on monitor mode" section.
Fonte: link