Common server ports

Port Numbers Used by Some Common Protocols 

Port  Name  Comment

1 tcpmux TCP port service multiplexer
5 rje Remote Job Entry
7 echo Echo service
9 discard Null service for connection testing
11 systat System Status service for listing connected ports

Iptables Basic Guide

Where are the main iptables files stored?

/etc/init.d/iptables is the INIT script which is used to start, stop the service and/or to save the rulesets.

/etc/sysconfig/iptables this is the file that holds the saved rulesets.

/sbin/iptables and this is the iptables binary.

Before you actually start configuring the rules, let's take a look at the current configuration:

# iptables -L