Original subtitles

Before doing a demonstration a quick recap of a writing table what is a writing table a writing table

is a list of networks that the reader knows about as well as information about how to reach those networks.

In other words a router may have a Network 10 1 1 0 or 24 in the routing table.

That entry may also contain information such as the outgoing local interface and the next top Rodda

to use to get to that destination.

Each entry in the writing table is a destination network.

If you are using a unique cost or writing protocol and once again includes the local interface to use

to get to the neighbor or the next hop to get to that destination.

Now there are various types of routes that are included in a writing table including directly connected

networks.

These networks are added to the writing table automatically and is a network that is directly connected

to one of the interfaces on the local router.

If the interface goes down well in other words fails or you shut down the interface.

In other words it's administratively down that a network is removed from the writing table.

The second type is static routes.

Static routes are routes that you as the administrator have manually added to the configuration of the

router.

Static Grotz are very good for small simple networks that don't change often.

However if your networks very large static routes don't work well because of the amount of work it is

to maintain those writing entries static Roths also do not dynamically adjust to changes in the network

topology.

So if you're telling a rodded to go right to get to a destination and the network is down the road it

will still send traffic to the right rather than going to the left as an example to get to the destination.

The third type is a default route.

You can manually configure a default route.

It's a special type of static route or a routing protocol can dynamically add it to the writing table

a default route is an optional route that is used when no explicit path to a destination is found in

the writing table.

So if a specific route like 10 1 1 0 slushed 24 is not in the writing table the default wrocht can be

used to get to the destination.

In this typology I have three routers Router one Rodda two to three I've configured loopback on each

router.

So quadruple one and right one could ripple to route it to quadruple three and rotatory first.

Ethan it is 0 0 on Rotto 1 and Rodda 2 is in the 10 1 1 0 slash 24 network.

If there is one on Rodda 2 and if 0 0 3 are in the 10 1 2 0 slushed 24 network has wrought a one show

IP interface brief.

I can see that IP address 10.0 wandered wondered.

One is configured on first East and it is 0 0 and 1 dog wandered 1.1 is configured on loop back to 0.

Show IP route in the output we can see that two directly connected networks have been added to the writing

table of Rato one 10 1 1 0 slushed 24 is directly connected to Fost.

Ethan it is 0 0.

Its important to remember that routers and layer 3 switches route based on networks and subnets and

not based on IP addresses show run interface Fost.

Ethan It is 00 shows me that the IP address configured on FASA Ethan it is 0 0 is 10 that wandered wondered

1 slash 24 but the IP address is not added to the writing table.

The network is added to the writing table as a directly connected network on fust.

Ethan it is 0 0 and its shown in the writing table we're denoted in the writing table as a C which means

connected network.

When you add an IP address to an interface and that interface is up the road has added to the writing

table.

So let's prove that interface loop back one IP address actually before I put the IP address on let's

have a look at the writing table do show IP ront.

Notice we only see two metrics in the writing table.

However if I configure an additional network so $1.1 1 to slash 32 on this new loopback and now use

the command to show IP route notice we have a third route in the writing table.

We have 1.1 1.1 slashed 32 and 1.1 one to slash 32 this network is configured to loop back zero.

And this network is configured on loopback back one.

The reason these display as IP addresses is because we configure it a slash 32 mosque.

However here we configure configured to slash 24 mosque.

So we see tenders one but 1.0 So as another example interface loop back to IP Address 10 dot one and

let's make this 10 one slice 24.

What does that add to our writing table do show IP route notice slash 24 network is added to the writing

table because we used a slash 24 mosque on the site.

The address if you need to face is shut down.

The rod is removed from the writing table.

So this route is currently in the writing table.

I'll shut it down to show IP route notice the network is removed because the interface has gone down.

No shut it interface comes up do you show IP route network is now available.

However at the moment we do not have rats in the writing table for Rodda two and three.

So lets add those ranched to the writing table.