VLANs and VPNs – CompTIA A+ 220-1101 – 2.6

Whether you are communicating locally or across long distances, there are network technologies that can get your data to the right place. In this video, you’ll learn about the use of VLANs on local networks and how VPNs can be used to protect all network flows.

A LAN is a Local Area Network. We commonly define this as a group of devices that are in the same broadcast domain. In this example, we have two different switches. One is the red switch and one is the blue switch. On the red network, we have two devices that are in one broadcast domain. And on the blue switch, we have devices that are on a completely different broadcast domain. We might want this separation for security reasons.

Certainly this would have a separation between these devices and these. We might want to limit the number of broadcasts that might be on a network. So we might segment the network into smaller pieces. And in many ways, this is a very straightforward way to manage the network. Because if somebody needs to be on the red network, we connect them to the red switch. And if someone needs to be on the blue network, we connect them to the blue switch.

However, looking at this diagram, we can immediately see a number of inefficiencies. We’ve of course purchased two separate switches. We are powering two separate switches, and we’re managing the configurations on two separate switches. All of these are duplicating the effort, in some cases duplicating the cost we would need to maintain both of these networks. We can also see on these switches that we’re connecting two devices, but we have a lot of empty interfaces on the switch. So we’ve paid for a lot of switch that ultimately we’re not using.

It would be much more efficient and cost effective if we could buy a single switch, maintain a single power source for that switch and a single configuration, and simply logically associate certain interfaces on that switch to the red network and logically associate other interfaces on that switch to the blue network. The switch itself would provide the separation between the red network and the blue network, and these devices still would not be able to communicate directly to each other.

We refer to this virtualization of the local area network as a VLAN. This is grouping the devices still in their same broadcast domain, but we’re doing this across the same physical device. This means that we won’t need separate switches. We can instead have exactly the same functionality on a single switch by implementing and configuring VLANs for each of these individual interfaces.

Let’s add even a third network. So on this switch, we’ve configured a red network, a blue network, and a green network. And you can see that we’ve connected different devices to these interfaces. As the network administrator, we’ve specifically configured the interfaces on the switch to match a certain network. So in this case, if you’re connected to port one, you’re on the red network. If you’re connected to port nine, you’re on the blue network. And if you’re connected to port 17, you’re on the green network.

Of course, instead of using colors we associate a VLAN with a number. So the red network may be VLAN 1, the blue network might be VLAN 2, and the green network might be VLAN 3. You can see that not only does this make it easier to manage the network, but now we can keep costs lower by having a single switch instead of purchasing three separate switches for these three VLANs.

A technology that has become rather commonplace on our networks today is a VPN or a Virtual Private Network. This is usually a combination of software and hardware that allows us to securely send information across a public network such as the internet. Everything sent over that VPN connection is automatically encrypted, which means if anyone in the middle happens to capture this information, they wouldn’t be able to see or understand anything in the conversation. If you’ve used a VPN, then you certainly are familiar with how that looks from the desktop of your operating system.

But somewhere it’s connecting to a separate device and the device we’re connecting to is a concentrator. This can be a standalone device or it may be integrated into a firewall or some other multi-use device. There are many different ways to deploy VPNs. The example we have here is a hardware device that may have specialized VPN or encryption hardware inside of it. But you can also configure VPN software that might be running on a server. Many VPN implementations have their own application that can be installed in an operating system, and you’ll find that these days most modern operating systems come included with some type of VPN client.

This means that you can still be secure when using your laptop in a coffee shop even if the wireless network in that coffee shop is one that is open and not encrypted. You would either use VPN software that’s always on and always connected or you would have the option on your laptop to enable or turn on the VPN capability. When you do that, it creates an encrypted tunnel back to the VPN concentrator, and now everything sent from your laptop will be encrypted across the wireless network of the coffee shop, the internet, and any other links until it reaches that VPN concentrator.

At this point, the VPN concentrator will receive that encrypted information. It will decrypt the data and send that information into the corporate network. Any device that needs to send information back to the laptop will send that information to the VPN concentrator. The concentrator will encrypt that data, send it over the encrypted tunnel, and when it reaches your laptop, the laptop will then decrypt that data so that it can be used locally. This entire process happens behind the scenes and is automatic when you enable your VPN software.