Hey it's Clint Garrett, Ace Networker here, and we're about to take a close
look at firewalls in this short video. And I'm going to give you a simple firewall tutorial
for beginners here in this short series, what they do, why they're needed. So stay tuned...
So what are firewalls? And why are they needed? To define a network firewall as simply as possible,
it is a filter in the form of a physical device or software that protects an internal network from
unauthorized access. It filters the traffic coming into and exiting your internal network to prevent
malicious attacks and programs on the internet or the external network that it's connected to
from affecting your internal network. Now with that being said, how does it do that exactly?
Well if we look at the most basic functionality of a firewall it looks at each packet and makes
a decision to block or allow that traffic based on a set of rules. Again that can be traffic arriving
on your network or coming into your network from outside, or inside traffic inside your network
traveling outside your network to the external network (which is again usually the internet).
Ok, so we basically know what a firewall is and what it does now. But there are different types
of firewalls and uses for them that you'll need to know to pass the Network+ Exam or the CCNA. When
you see the actual hardware component or appliance firewall (a device that is built as a firewall,
in other words that's why it was built), it is known as a "network
based firewall" Typically you will see a network-based firewall placed between your
internal LAN (your local area network) and the external network (again usually the internet).
If you use or operate a network-based hardware firewall it is usually used as the first line of
defense on your internal network. Network-based firewalls really tend to serve this purpose well
to protect your network from external attacks and malicious intent. However they are of little use
to any attacks coming from inside your Local Area Network. This is where "host-based" or
software firewalls are used. Host-based software firewalls are installed on a host to provide
firewall services for just that machine. A good example of a host-based software firewall
is the Windows firewall found and used on Windows operating systems. The most often encountered
firewall a network admin or technician will deal with is the host-based software firewall.
You will also see firewalls that are known as "stateful firewalls" Stateful firewalls
operate at Layer 7 of the OSI Model and they are application or context aware. A stateful firewall
uses what's known as Deep Packet Inspection (DPI) to filter the traffic based on the service or the
application where the traffic originated. A good example of where Deep Packet Inspection comes
in handy is on something like Bit Torrent that used to be used that could overload your network
because it used port hopping. A stateful firewall using deep packet inspection is invaluable
in that type of scenario. And last but certainly not least you will see what are called "stateful
inspection firewalls" This is typically on the newer latest firewalls that you see out there.
A stateful inspection firewall is capable of being able to tell if a packet is part of an existing
connection. In other words, the firewall can look at a packet and know what that package state is in
relation to other packets. Now I'll get into more detail on things like "windowing" used on Session
management across a connection when it comes to Session Layer and the Transport Layer in the OSI
Model, but for now just know that a stateful inspection firewall can tell and be aware of
these multiple packets in a connection session. This contrasts the older "stateless inspection
firewalls" that looked at a packet and they could care less what that packet's relation was to any
other packets. So those are the basics of the different types of firewalls you'll encounter
and possibly use on a computer network. Now as we get into more detail in our study of computer
networking you'll see how a firewall is only part of an overall toolkit for providing security on
a computer network. When we get into network security we'll talk more about how firewalls are
but one tool in what they call UTM (Unified Threat Management). Unified Threat Management encompasses
not only firewalls but other security services such as VPN, IPS, load-balancing, antivirus
and several other features all depending on the applications and devices being used
as well as the makes and models. So thank you for watching and I'll see you in the next video!