/etc/sysconfig/iptables

-A RH-Firewall-1-INPUT -p tcp –dport XX -s XXX.XXX.XXX.0/24 -j ACCEPT
# -p protocol
# –dport destination port
# –dports ssh,www,https,pop3,smtp,imap,imaps,pop3s
# -s source
# -j ACCEPT, DROP