Static Routing - CompTIA Network+ N10-009 - 2.1

Summary

This script explains the role of routers in forwarding traffic between IP subnets. It simplifies the process into steps, highlighting the importance of routing tables for directing packets to their destinations. The script discusses static routing, where administrators manually configure routes, which is suitable for small networks but can be challenging for larger ones. It also touches on the limitations of static routing, such as the need for manual updates and lack of automatic rerouting in case of network changes. The example of configuring static routes on router 1 to reach additional networks behind routers 2 and 3 is provided to illustrate the concept.

Takeaways

• 📍 Routers play a crucial role in forwarding traffic between IP subnets.
• 🔍 The first step in routing is identifying the destination IP address of incoming traffic.
• 📖 Routers use tables to determine the best route for packets, often involving a 'next hop' to another router.
• 🏠 Directly connected subnets are easy for routers to manage, as they are part of the local network.
• 🌐 For non-local destinations, routers rely on routing tables to find the next hop IP address.
• 🚫 If a router cannot find a next hop in its table, it discards the packet.
• 📈 The routing table is vital for network communication and is often consulted during troubleshooting.
• 🛠️ Static routing is a method of manually configuring routes within routers, useful for smaller or remote networks.
• 🔒 Static routing can be more secure as it doesn't rely on dynamic updates, reducing the risk of misconfiguration.
• 🔄 However, static routing can be challenging to maintain in large networks due to the manual effort required.
• ⚙️ Misconfigurations in static routes can lead to routing loops within the network.

Q & A

What is the primary function of a router?

The primary function of a router is to forward traffic between one IP subnet and another.

How does a router identify the destination IP address for incoming traffic?

A router identifies the destination IP address by looking into the packet and noting where the traffic should be sent.

What does a router do if the destination IP address is on a directly connected subnet?

If the destination IP address is on a directly connected subnet, the router simply sends the packet onto that local subnet.

What is the process if the destination IP address is not on a locally connected subnet?

If the destination IP address is not on a locally connected subnet, the router examines its routing table to determine the best next hop and sends the traffic out through that interface.

Why is the routing table important in the context of router operation?

The routing table is important because it helps the router determine the best path for packets to reach their destination, and without a valid entry for a destination IP address, the router will discard the traffic.

What is static routing and how does it differ from dynamic routing?

Static routing is the administrative creation of a routing table where an administrator manually configures routes inside every router. It differs from dynamic routing, which is not mentioned in detail in the script but typically involves routers automatically exchanging routing information to build and update the routing table.

Why might static routing be a good choice for certain networks?

Static routing might be a good choice for smaller networks or remote locations with a single internet connection because it is quick to configure, has no overhead from dynamic routing protocols, and is relatively secure as there are no dynamic updates to worry about.

What are some challenges associated with configuring static routes on larger networks?

Configuring static routes on larger networks can be challenging because it requires manually configuring each router, which can be time-consuming and error-prone. It also requires manual updates if there are changes to the network.

What happens if a router's static route configuration is incorrect?

If a router's static route configuration is incorrect, it may create routing loops or cause traffic to be discarded if the destination network is not in the routing table.

How can static routes be configured on a router?

Static routes can be configured by SSHing into the router and manually adding routes at the command line, specifying the destination network and the next hop IP address.

What is the purpose of adding static routes for networks behind other routers?

The purpose of adding static routes for networks behind other routers is to provide a path for the router to know where to send traffic destined for those networks, ensuring that packets reach their final destination.

Outlines

00:00

🌐 Understanding Routers and Routing

This paragraph explains the fundamental role of routers in forwarding traffic between IP subnets. It simplifies the process into identifiable steps: identifying the destination IP address of incoming traffic, consulting routing tables to determine the best path, and sending packets to either a directly connected subnet or the next hop in the route. The importance of the routing table is emphasized, as it dictates where packets are sent. The paragraph also introduces the concept of static routing, where an administrator manually configures routes within routers, which is suitable for smaller or remote networks but can be challenging to manage at a larger scale.

05:02

🔄 Static Routing and Its Challenges

The second paragraph delves into the specifics of static routing, including the potential for misconfigurations that can create routing loops. It highlights the static nature of these routes, which means any network changes require manual updates to the routing table. The paragraph also discusses the lack of automatic rerouting in case of network issues. An example is given on how to configure static routes for router 1 to direct traffic to networks behind router 2 and router 3, illustrating the process of manually specifying next-hop addresses for certain destination IP ranges.

Keywords

💡Router

A router is a networking device that forwards data packets between computer networks. In the context of the video, routers play a crucial role in determining the paths for traffic to travel between different IP subnets. The script describes how routers examine destination IP addresses and use routing tables to decide where to send the packets, ensuring they reach their final destination.

💡IP Subnet

An IP subnet is a subdivision of an IP network, where each device on the network is assigned an IP address. The video script explains that routers are responsible for forwarding traffic between different IP subnets, which is a fundamental aspect of networking. The example of Sam trying to communicate with Jack illustrates how routers handle traffic for different subnets.

💡Routing Table

A routing table is a set of rules that a router uses to determine where to send data packets. The video emphasizes the importance of routing tables in directing traffic to the correct destination. The script mentions that if a router cannot find a next hop for a destination IP address in its routing table, it will discard the packet.

💡Destination IP Address

The destination IP address is the IP address of the final recipient of a data packet. The script describes how routers first identify the destination IP address of incoming traffic to determine where to send the packet. This is a critical step in the routing process, as it dictates the path the packet will take.

💡Next Hop

The next hop refers to the next router or device that a data packet will be sent to on its way to its final destination. The video script explains how routers use their routing tables to determine the best next hop for a packet, which is essential for forwarding traffic to the correct subnet.

💡Static Routing

Static routing is a method of configuring routes on a router manually by an administrator. The video script discusses static routing as a way to create a more complete routing table. It involves manually entering the routes into each router, which can be quick and straightforward for smaller networks but challenging for larger ones.

💡Administrative Creation

Administrative creation refers to the manual configuration of network settings, such as creating static routes. The video script mentions that static routing is an administrative creation of a routing table, where the network administrator manually configures the routes inside every router.

💡Stub Networks

Stub networks are networks that have only one route to the rest of the internet or a larger network. The script describes how static routing is common for remote locations with a single internet connection, which are referred to as stub networks. These networks do not require dynamic routing updates, making them more secure.

💡Misconfiguration

Misconfiguration refers to setting up network devices or systems incorrectly, which can lead to issues like routing loops. The video script warns about the potential for misconfiguration when setting up static routes, as the administrator must ensure that the correct routes are added to every router.

💡Rerouting

Rerouting is the process of changing the path that data takes through a network. The video script explains that static routes do not automatically adapt to network changes, so if there is a need for rerouting, it must be done manually by updating the routing table on the routers.

💡SSH

SSH (Secure Shell) is a protocol used to securely access and manage devices over a network. The video script mentions using SSH to access router 1 and configure static routes. This is an example of how network administrators interact with routers to manage their configurations.

Highlights

Routers forward traffic between IP subnets.

Routers perform a series of simple steps to forward traffic.

First step is identifying the destination IP address.

Routers examine tables to determine the best route for packets.

If the destination is directly connected, the packet is sent to the local subnet.

If the destination is not locally connected, the router determines the best next hop.

The next hop is the IP address of the next router in the path.

The routing table is crucial for determining where packets should go.

If no next hop is found, the router discards the traffic.

A network diagram with three routers and three individuals is presented.

Router 1 is connected to three different subnets.

Router 1's routing table includes routes for directly connected networks.

Problems arise when trying to communicate with networks not in the routing table.

Static routing is an administrative creation of routing tables.

Static routing is quick to configure and has no overhead from dynamic routing protocols.

Static routing is common for remote locations with a single internet connection.

Static routing is secure but can be challenging to configure on larger networks.

Static routes do not change once configured and require manual updates for network changes.

Configuring static routes involves manually adding routes to routers.

An example of configuring static routes for router 1 is given.

Static routes are manually configured to direct traffic to the correct networks.

Transcripts

The routers that we use in our homes and our offices

have an important job of forwarding traffic between one

IP subnet and another.

It's a relatively straightforward process,

although there is a lot of technology under the surface

that makes this happen.

But if we were to look at this in a very simplified form,

we could see that the router is performing a series

of relatively simple steps.

The first step is to identify what the destination IP

address might be for incoming traffic into the router.

It looks into the packet, identifies what the destination

IP address is, and makes a note of where it

should be sending this traffic.

The router then examines some tables

to determine what the best route will

be for this particular packet.

If the destination IP address of this particular packet

is associated with a subnet that is directly connected

to this router, then the router simply sends the packet

onto that local subnet.

But in many cases, the destination IP address

is on a subnet that is not locally connected

to this router.

The router will examine that routing table,

determine what the best next hop might be,

and then send the traffic out that particular interface.

This next hop is the IP address of the next router

down the line.

And when that router receives this packet,

it performs the same process again,

until the packet finally makes its way

to its final destination.

As you can imagine, that routing table becomes very important.

And when we're troubleshooting routers,

we refer often to the routing table, what the next hop might

be, and determining where these packets should be going

once they leave our router.

If a router refers to its table and does not

find a next hop for that destination IP address,

it will simply discard that traffic.

So you can see why having a valid routing table

becomes very important.

Let's look at this network diagram.

There are three separate routers in this network diagram

and three individuals that would like

to communicate with each other.

In this case, let's focus on router 1.

You can see router 1 is connected

to three different subnets.

We have a subnet 10.10.10.0/24.

There's another subnet between router 1 and router 2--

that is the 10.10.40 network--

and then another subnet between router 1 and router 3.

That's the 10.10.50 subnet.

Those three subnets are directly connected to router 1.

So if we were to look at the routing table for router 1,

it would see the route for 10.10.10.0/24, 10.10.40.0/24,

and 10.10.50.0/24.

And all of those networks are locally connected

to this router.

The problem occurs if Sam would like to communicate to Jack.

Although router 1 knows about the local networks,

it has no idea that there are more networks on the other side

of router 2 and of router 3.

And those particular networks of 10.10.20.0/24 and 10.10.30.0/24

are nowhere in this routing table.

This means if Sam wants to send traffic to Jack,

Sam will put this packet out on the network.

It gets to router 1.

Router 1 examines the destination IP address

of 10.10.20.2 and then looks through its table and realizes

there is no 10.10.20 network in the routing table.

And the packet is discarded and never makes its way

down the network.

One way that we could create a more complete routing table

is to build it ourselves.

This administrative creation of a routing table

is referred to as static routing.

And if you would like to build static routes

as the administrator of your routers,

then you will manually be configuring these routes inside

of every router that you use.

Static routing is a very quick way

to configure a route inside of the router.

And if you're managing a smaller network,

this might be a perfectly reasonable way

to manage where the routes might be.

Because we're static routing, there's no overhead

that you would normally see from a dynamic routing protocol.

We'll talk about dynamic routing in a future video.

So there's no CPU cycles.

There's no memory usage.

We are simply adding the route ourselves.

And we don't have to do any additional processing

to the routing table from there.

This is very common for remote locations, where

you might have a single internet connection

into that remote site, and all communication

takes place over that single connection.

We often refer to these as stub networks.

And because we don't have to worry about any type of dynamic

routing updates or having any changes to the router

configuration because of those updates,

this is a relatively secure form of routing.

However, this can be challenging to configure on larger networks.

Configuring a handful of routers with their own static routes

is relatively straightforward.

But if you're managing hundreds or thousands of routers,

manually configuring a static route in each of those routers

could take quite a bit of time.

This also relies on you adding the correct routes

to every router.

There have been times when I've configured static routes,

and I've set up my own routing loop within my network because

of a misconfiguration.

And as the name implies, these routes are static.

They don't change once you've configured them.

So if there are changes to your network,

you'll need to manually log into your routers

and make those configuration updates

to the routing table that match the changes to your network.

This also means that there is no automatic rerouting if something

happens on your network.

You will need to manually configure these routes

if anything needs to be routed in a different direction.

So let's configure some static routes for router 1.

We know that we have our three locally connected routes.

But we also have these additional two routes,

one that's behind router 2 and one that's behind router 3.

This would be the 10.10.20 network and the 10.10.30

network.

So we might SSH into router 1.

And at the command line, we would

begin to add additional static routes.

For example, we might tell router 1 that if it receives any

packet coming through with a destination IP address that

matches the range of 10.10.20.0/24,

then send that particular packet to 10.10.40.2.

So if the packet does come through with that destination

that needs to go to the local network that Jack is connected

to, it will send all of that traffic to the IP address

10.10.40.2, which is located on router 2.

At that point, router 2 will examine its own routing table

and know that the 10.10.20 network is locally connected

and send that packet on its way.

We can do the same thing with the 10.10.30.0 network.

So we will manually configure a static route that if any

destination traffic is going to 10.10.30.0/24,

then send all of that traffic to 10.10.50.2,

which means all of that traffic will go to router 3.

Now that we've configured those static routes

in router 1, any time those additional networks are seen

as a destination IP address, router 1

will know exactly where to send that traffic.