Command for using iptables
1. opening some port
#iptables -A INPUT -i eth0 -p tcp –sport 443 -m state –state your -j ACCEPT
2. deleting
#iptables -D INPUT -i eth0 -p tcp –sport 443 -m state –state your -j ACCEPT
3. sharing the internet
#sysctl -w net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
service iptables save
iptables is a command to set route in your computer lan and internet. Even you can arrange your firewall using this command.