Laptops vary in their ability to operate in Wifi promiscuous mode, but even if they don’t then a cheap Wifi dongle can be purchased to allow it. “Bring Your Own Device” (BYOD) is a growing trend allowing employees to bring their own laptops, notepads and smartphones to the office instead of using the usual desktop computer and telephone. Wifi, by its very nature will receive data from many areas of the network. In this case, promiscuous mode would have no effect as your computer would not be receiving datagrams from the rest of the network. In an attempt to stop this the network administrator will only allow your desk computer to receive datagrams associated with its VLAN or destination MAC address. Clearly this could be a major security issue as anybody operating in promiscuous mode with a packet analyzer would be able to view and decode all packets within a network. To bypass this limitation promiscuous mode enables the NIC to pass all ethernet frames to the CPU regardless of source and destination MAC addresses. This would be serious limitation for any network monitoring device as it will not be able to monitor datagrams on the rest of the network. Network ethernet interface cards (NIC) generally only pass two types of datagram to the CPU datagrams with the NICs address, and broadcast packets. With the intuitive graphical interface, it’s very easy to drill down into an IP packet, and then ethernet frame to see the actual data.

Wireshark allows engineers to see what is going on under the hood of a network by monitoring an ethernet port in promiscuous mode and then decoding and displaying the packets.

Originally called Ethereal and first released in 1998, the name was changed to Wireshark as Ethereal was already a registered trademark. Wireshark is a free open source packet analyzer running on Linux, UNIX type systems and Windows.

Wireshark promiscuous mode linux