Many if not all network traffic capture utilities require that the network adapter has the promiscuous mode enabled.
To check if the promiscuous mode is on run:
netstat -i
Kernel Interface table Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth0 9001 9095 0 0 0 10367 0 0 0 BMRU
Look at the Flg column – if the P flag is missing the mode is not enabled.
To enable it run:
ifconfig eth0 promisc
or
ip link set eth0 promisc on
