VLANs and VPNs - CompTIA A+ 220-1201 - 2.4

Let's start our conversation referring to LANs or local area networks. This is a group of devices that are connected together into a single broadcast domain. That means if we send a broadcast out on one of these devices to this LAN, all of the other devices in this LAN will also see the broadcast. Over on this side, we

have a separate switch. And because it is a separate switch, it is a separate broadcast domain. Which means any device on this network that sends a broadcast would only be seen by other devices connected to that same broadcast domain. That means if we send a broadcast over on the red network, no devices on the

blue network will be able to see that broadcast because this is a single broadcast domain that is separate from all of the other broadcast domains. From a security and an organizational perspective, this is a very good design. Everyone on the red network is connected to the red network switch and everybody on the blue network is connected to the

blue network switch. But one of the challenges with this is that it doesn't make very efficient use of our switches. For example, we have a switch here with 24 interfaces and only two devices are connected to that device. We have a separate 24- port switch on this side. And that switch also only has two

devices on it. If we wanted to save money and save space in our rack, we would put all of these devices on the same physical switch. But when we do that, we have a problem with all of these devices being on the same broadcast domain. Fortunately, many of our modern switches have the ability to

configure a virtual local area network or a VLAN. A virtual local area network means that we can assign different interfaces on a switch to belong to a particular VLAN. This is a very good example of combining two separate switches into one single switch, but then assigning different interfaces to different VLANs. That means we can have