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TechKnowSurge Catalog Videos What’s a Network Router?
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What’s a Network Router?

Routers are Layer 3 devices that forward packets between networks by examining IP addressing information to determine the best path to a destination. Business-grade routers support multiple network interfaces and modular expansion cards, allowing them to interconnect several networks simultaneously.

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About this video

A router is a Layer 3 networking device that forwards packets between separate networks by examining IP addressing information to determine the best available path toward a destination. When a device needs to communicate with another device on a different network, the data frame is passed to a router, which reads the Layer 3 header, evaluates its available paths, and forwards the packet toward the next hop. This process repeats at each router along the route until the packet arrives at the network segment where the destination device resides. Business-grade routers are designed with scalability and flexibility in mind. A typical enterprise router includes multiple built-in network ports for connecting to different networks, along with additional ports dedicated to device management. Beyond the built-in interfaces, modular expansion slots allow administrators to install interface cards, such as T1 cards, to support additional network connections. A single business router with built-in ports and one or more expansion cards can therefore serve as the interconnection point for several distinct networks, making it a central component in enterprise and wide-area network infrastructure.

What you'll learn

What's covered

Routers

Aligned to

CompTIA Network+
1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.
2.1 Explain characteristics of routing technologies.
1.2 Compare and contrast networking appliances, applications, and functions.
Cisco CCNA
3.2 Determine how a router makes a forwarding decision by default
1.1 Explain the role and function of network components
Cisco CCST Networking
4.4 Explain basic routing concepts
4.3 Identify the various ports on network devices

Key terms

Router
A network device that forwards data packets between networks based on IP addresses.
Layer 3
The Network layer of the OSI model, responsible for logical addressing and routing packets between networks.
Packet
A unit of data formatted for transmission over a network, containing a header, payload, and sometimes a trailer.
IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.
Network Interface Card
NIC
A hardware component that connects a computer to a network.
T1 Card
A modular expansion card inserted into a router to add a T1 WAN interface, extending the router's network connectivity.

Transcript

A router routes packets. If this device is trying to communicate to this device right here, what's going to need to happen is it's going to need to traverse several networks. The frame gets sent to the router, and the router is going to take a look at the layer 3 information to figure out which direction it needs to go. It looks like it has a couple of different options here, so it'll choose one of those options, the option it feels is the best. That router will do the same thing to send it to the next router. And then this router happens to be attached to this network, and we'll send it to that end device.

So that's what a router does: it routes the packet based off of this layer 3 information. Because it's based off of the layer 3 information, we say that the router is a layer 3 device.

Examples of routers

Here are a couple of examples of routers. I've got a business router and a home router here. I'm going to set the home router aside for now, but we have the business router right here.

A couple of interesting things about this business router. We've got two ports, so this is capable of connecting to two different networks here, and these are built-in ports right here. But then we also have two other ports. These are more for management of the device, so they're really not two different networks here; it's just the two networks that we see right here.

And then we have spots to slide in other features. We've got a T1 card in right here. So this T1 card that we have slid into here is another network. So now, in total, this will support three, because we've slid in this T1 card, and it's got capability of sliding another card into this right here.

So this would be a router interconnecting our different LANs. And this is what that looks like on the other side. Just a little face plate here, so there's really not too much to see on the other side of this particular router.

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