iptables

iptables -I INPUT -s xxx.xxx.xxx.xxx -j DROP

insert (-i) into chain INPUT with source (-s) ip xxx.xxx.xxx.xxx and jump (-j) to target DROP

iptables -L INPUT

List the entries in the INPUT chain

iptables -F INPUT

Flush the INPUT chain

iptables -L -n**

List by IP address

iptables-save > /etc/iptables.conf

Saves

iptables-restore < /etc/iptables.conf

Restores

use the output chain to drop all requests on port 80

1. A OUTPUT -p tcp -m tcp –dport 80 -j DROP
2. A OUTPUT -p tcp -m tcp –dport 443 -j DROP

then accept ips that you want

1. A OUTPUT -s 217.158.112.246 -d 212.118.245.130 -p tcp -m tcp –dport 80 -j ACCEPT

Adding on command line

iptables -I OUTPUT -s 217.158.112.246 -d destinationIP -p tcp --dport 80 -j ACCEPT