iptables port manipulation

You may find there's no /etc/sysconfig/iptables in a CentOS install with iptables disabled upon install, but you want to redirect a port, e.g. to get port 80 working in tomcat.

Do:

service iptables start
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
iptables-save > /etc/sysconfig/iptables
service iptables restart

To open port 80, add the following to the *filter section before COMMIT:

-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT

then service iptables restart