Continue with How to Start Filtering and Learn Carefully

continue with Inside The Computers, still with How to Start Filtering and of course Learn Carefully. Inside the NAT table, you can modifying the source and destination address or port from packages which in or out. The benefit from this facility is to hide IP address or we can call with IP masquerading. The hidden of the IP address become another knowing shape is the basic security system. Not everyone can know the real IP address. NAT table has three chain which is PREROUTING, POSTROUTING, and OUTPUT.

The third table is Mangle which will make the packages marking one by one. The destination of that marking is the tables has they own characteristic, so the package can be proceed to the next step according to the policy.

Mangle table has the ability to use all the chain in IPTables such as INPUT, OUTPUT, PREROUTING, etc. by using this table, we can do a lot of thing such as doting routing changing as you want, or you give a special treatment to one of the package or more or we use to know as QoS, etc.

Learn Carefully
IPTables is hard and too complex to understand. You need times to learn it, and this article only introduce you not to master it. IPTables is the solution for sophisticated firewall but cheap. You do not need to buy an expensive peripherals for firewall if you want to use a simple connection. IPTables can do it for you.
What you need is to learn it more so you can use it. Learn the command and the syntax carefully, so if you already know IPTables, use it.