Promiscuous mode or promisc mode is a feature that makes the ethernet card pass all traffic it received to the kernel. It is usually used by a packet sniffing program like Wireshark, and tcpdump. … A network card usually is in promiscuous mode when: If it was manually configured in that mode using ifconfig command.

What does promiscuous mode mean?

In an Ethernet local area network ( LAN), promiscuous mode is a mode of operation in which every data packet transmitted can be received and read by a network adapter. Promiscuous mode must be supported by each network adapter as well as by the input/output driver in the host operating system.

How do I know if I have promiscuous mode?

tl;dr: Kernel tracks promiscuous mode using flags on the device. For promiscuous mode, IFF_PROMISC, 0x100 should be set. For a given interface, check the flags to see if the promiscuous bit is set. $ cat /sys/devices/virtual/net/veth0/flags 0x1303 # 0001 001[1] 0000 0011 # device is in promiscuous mode.