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TechKnowSurge Catalog Videos DEMO: Routes
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DEMO: Routes

Routing tables store the routes a router uses to forward packets toward their destination, identifying each path by a next-hop IP address or exit interface. This content examines what routing table entries contain and demonstrates how to read them on both a Windows host and a Cisco router.

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About this video

A routing table is the reference a router consults every time it receives a packet, matching the packet's destination against a list of known networks to determine the best path forward. Each entry in that table is called a route, and it identifies not only the destination network but also how to reach it — either through the IP address of the next hop or through a designated exit interface on the router itself. Both methods accomplish the same goal of pointing traffic in the right direction toward its destination network. Understanding the structure of these entries is foundational to understanding how routers make forwarding decisions at a basic level. The structure of routing table entries becomes clearer when examined directly on live systems. On a Windows host, the route print command displays the IPv4 routing table, where each line represents a single route containing a destination network, subnet mask, gateway, interface, and metric. On a Cisco router, the show ip route command produces a similar view, revealing destination networks alongside next-hop addresses, exit interfaces, metrics, and information about how each route was learned — whether through a routing protocol, direct connection, or another method. Reviewing both outputs side by side reinforces how the same core concepts apply across different platforms and device types.

What you'll learn

What's covered

Routing Tables & Routes

Aligned to

Cisco CCNA
3.1 Interpret the components of routing table
1.10 Verify IP parameters for Client OS
CompTIA Network+
2.1 Explain characteristics of routing technologies.
Cisco CCST Networking
4.4 Explain basic routing concepts
5.5 Run basic show commands on a Cisco network device
CompTIA A+ Core 2
1.2 Given a scenario, use the appropriate Microsoft command-line tool.

Key terms

Router
A network device that forwards data packets between networks based on IP addresses.
Routing Protocol
A protocol used by routers to communicate and share routing information to determine the best path for data.
IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.
Subnet Mask
A 32-bit number that divides an IP address into network and host portions.
Default Gateway
The router that a device uses to send traffic to destinations outside its local network.
Routing Table
A database stored in a router that lists known network destinations, the metric (cost) to reach them, and the next-hop address or outgoing interface to forward packets toward those destinations. Routers consult this table for every packet they forward.
Next Hop
The IP address of the immediately adjacent router that a packet is forwarded to on the way toward its final destination. A router's routing table entry for each network destination includes the next-hop address so the router knows where to send the packet.
Exit Interface
The physical or logical router interface through which a packet is forwarded toward its destination.
Metric
A value used by a router to determine the preferred path to a destination when multiple routes exist; lower values typically indicate a more preferred route.

Transcript

Routes in the Routing Table

We know that a packet that comes into the router is going to look up on the routing table to determine what is the next best hop. But what is inside of that routing table? Well, the routing table has a bunch of routes in it. It's just how it can get to this location, this network. So within that routing table, it'll have a list of networks and where it is that that packet needs to go in order to send it in the direction towards that network. We call those routes. The routes are just what networks are within the reach of that router, and what direction it needs to go, or what's the next best hop. And so the information will be looked up and then it will send it to the next best hop.

Next Hop or Exit Interface

Now, as we mentioned, this routing table has a list of networks that are in it, and then where the destination is, what the next hop is. And it can specify this by one of two different ways. Number one is it could just specify what the next hop address is, how it's going to get to that next hop address. Or it could specify it by the exit interface. So often we'll see an IP address for the next hop interface, or we'll see just the exit interface outside of this router right here. But that's what you'll find within these routing tables. So it knows, if I'm trying to get to this network, what I need to do is send it to this destination IP address next — that's my next hop — or I need to send it out this interface.

Viewing Routes on a Computer

I thought it'd be a great idea to take a look at what these routes actually look like. So I'm going to hit the start button here. I'm going to type in cmd and bring up a command prompt. And then I'll just type in route print and hit enter. And what we can see here, I'm going to scroll up to the IP version 4 routing table. So this is the routing table, and in here, we've got a bunch of routes. Each one of these lines is a separate route.

So what do we have part of this? We have the destination network, so this is the network destination. If it's going to something in the 10.0.0.0 range, then this is the network mask. This is the gateway for that. So it's got a bunch of information here: the gateway on how to get to that network, the interface that it's going to use, and something called a metric. We don't need to be too concerned about all of this at this point in time, but just know that each one of these is a route in this routing table.

Viewing Routes on a Router

Let's also take a look at a route on a router. So here I've SSHed into this router right here. If I do a show ip route, this is what comes up. So this is the routing table, and in this routing table here are all of the different routes. So what do we have here? Once again, we have the destination network here. So these are all the destination networks. We've got some information here — this is what's actually the metric there — but it tells us what the next hop is. So the next hop here is 10.240.0.1, and that exit interface needs to go out FastEthernet0/1 to reach this 10.240.0.1, to reach this network right here.

There's quite a bit of other information in here. We see how it learned of this route, and if it's a link local, and if it's directly connected. So we've got some other information in here, but essentially the goal here is just to take a look at each one of these.

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