Lista de excessão Iptables

iptables.sh

iptables -A INPUT -p TCP --dport (port) -s A,B -j ACCEPT
iptables -A INPUT -p TCP --dport (port) -j DROP

After any days....... I add IP C
iptables -I INPUT -p tcp --dport (port) -s C -j ACCEPT
Or add in line 1
iptables -I 1 INPUT -p tcp --dport (port) -s C -j ACCEPT

CentOS
service iptables save

Debian
iptables-save > /etc/iptables.rules
nano /etc/network/if-pre-up.d/firewall

#!/bin/bash
/sbin/iptables-restore < /etc/iptables.rules

chmod +x /etc/network/if-pre-up.d/firewall
reboot
iptables -L