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TechKnowSurge Catalog Videos What’s a Firewall?
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What’s a Firewall?

A firewall is a network security device that controls inbound and outbound traffic, blocking unauthorized access while allowing legitimate communication to pass through. It serves as the primary barrier between a private network and external threats.

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About this video

A firewall is a network security device that sits at the edge of a network and controls which traffic is allowed to enter or leave. By default, a network without security controls is open, meaning any external system could potentially communicate with internal resources. A firewall addresses this by enforcing policies that block unsolicited inbound traffic while permitting outbound connections and their associated return traffic, with inspection mechanisms in place to verify that returning data corresponds to requests that originated from inside the network. While a router can be hardened with access control lists to approximate some firewall behavior, a dedicated firewall device offers capabilities that go well beyond basic packet filtering. Next-generation firewalls perform deep packet inspection, examining the actual content of network traffic rather than just its source, destination, and port information. This additional layer of analysis allows them to detect and block threats that simpler filtering mechanisms would miss. In practice, firewall hardware ranges from consumer-grade wireless routers with limited built-in protection to enterprise firewall appliances with multiple network interfaces capable of segmenting traffic across several distinct network zones. Understanding the distinction between these device types and their respective capabilities is essential for designing and maintaining a network security posture appropriate to the environment.

What you'll learn

What's covered

Firewalls Overview

Aligned to

Cisco CCST Networking
6.1 Describe how firewalls operate to filter traffic
CompTIA Network+
4.1 Explain the importance of basic network security concepts
1.2 Compare and contrast networking appliances, applications, and functions
4.3 Given a scenario, apply network security features, defense techniques, and solutions
Cisco CCNA
1.1 Explain the role and function of network components
5.6 Configure and verify access control lists
Cisco CCST Cybersecurity
2.3 Describe network infrastructure and technologies
Cisco CyberOps Associate
4.3 Compare deep packet inspection with packet filtering and stateful firewall operation

Key terms

Firewall
A network security device that monitors and controls incoming and outgoing traffic based on predefined security rules.
Access Control List
ACL
A set of rules that defines which users or systems are granted or denied access to a resource.
Router
A network device that forwards data packets between networks based on IP addresses.
Packet Filtering
A firewall technique that inspects packets and allows or blocks them based on source, destination, and protocol.
Stateful Firewall
A firewall that tracks the state of active network connections and makes filtering decisions based on context.
Deep Packet Inspection
DPI
Deep Packet Inspection is a network traffic analysis technique that examines packet payloads beyond the header layer, enabling content-aware filtering, intrusion detection, and application identification.

Transcript

Why a Firewall Matters

A firewall is critical to today's networks. Without a proper firewall, you're going to get hacked and you're going to have people trying to get into your network. It's just the way things are nowadays, so it's critical that we have a firewall on our network. But what is a firewall?

When we set up our network, by default, if we don't take any security measures, things are open. There's communication that happens across this network, and if we were to connect up into the internet and the cloud, that means that things would just have access to all of our network, and that's not what we want. We don't want to give everyone access to our network.

What a Firewall Does

A firewall is a piece of equipment that allows us to block and allow certain traffic. So what we do is we set up a firewall, and it's going to block certain traffic from being able to get inside our network. It'll allow traffic from inside our network to get out and return traffic to come back to us, but it will do some inspection to make sure that the traffic coming back to us is the traffic that we requested. So that's what a firewall does: it protects our network from just anybody being able to access it.

Examples of Firewalls

The first one here is a wireless home router, and I'm going to set that aside. Then I have a router right here, and it's not really a firewall, but we're going to talk about that in a second. And then we have right here an actual firewall. This firewall has several ports on it, so we can divide this out into many different networks. It essentially performs all the functions of what a router performs, but then it also does the firewall aspect, where it guards our network and blocks off our network from outside intrusion.

Using a Router as a Makeshift Firewall

The reason why I brought the router in here as well is because we can set up a router to do a lot of the functionality that the firewall does. We can use a router and lock it down and use things like access control lists in order to create a makeshift firewall for our network. But the advantage of an actual firewall is that it does a lot more deep packet inspection, and it's a next-generation firewall. We're not going to get into all the details of what all that means, but it goes the extra mile, the extra effort, in making sure that our network is safe and protected. So that is what the difference is between this firewall, which does routing, and this router, which can do some of the firewall functions.

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