One of the popular questions we see from day to day, is what exactly is a hardware firewall and what is the purpose. As most guess, they are very similar to a software firewall you may be running on your local work station, however they do differ quite greatly in how they are used and the protection they provide.
A hardware firewall is a relatively simple piece of hardware, they are placed between the out side world (Usually the internet) and the section of the network you are needing to protect. They are specially built to block unwanted protocols and network activity from entering and/or leaving the protected network segment behind the firewall.
Firewalls use a configuration file that contains a set of rules, better known as an ACL (Access List). The ACL is much like any configuration file in the sense it contains all the information needed in order for your firewall to know what information to block and which to forward on to your back-end secure network.
One of the most important things to remember when you begin working with your first firewall is: ACL’s are read from the top down, so when you are configuring your firewall, always remember that a rule farther down in the list will NOT override an above rule. So if you block all access in line #1 and then allow access in line #2, line #2 will not allow access as in line #1 you already blocked it.
In many cases you will setup the firewall to block all incoming requests from the outside world beyond those you may want to have access. For instance, if you are running a web server you may want to block all access to the server (SSH especially) except for port 80 (http) and 443 (SSL). This way anyone trying to “hack” into your web server will have extremely little access to work with in order to breach your web server.

Now you may be wondering, “If I block all other ports, how am I going to access my server and/or network behind the firewall?” – This something that can be accomplished in a few different ways:
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