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So I copied this script from the Python website.

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Now for this initial script, I'm going to do the editing directly in the network automation container.

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Ellis shows us that we have no files on the network automation container.

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I'll create a file called Python 31py and I'll paste the script from the Python website into the network

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automation container.

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One of the advantages of using Python over other programming languages is all of the modules and additional

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code that you can leverage.

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So rather than writing everything yourself, you can simply import a libraries such as the Telnet library

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into your Python script.

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So in this example, we're going to import get pass.

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We're going to leverage that here by asking the user to enter their password rather than storing the

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password in the script.

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We're going to ask the user to enter their password and then save that in what's called a verbal.

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A variable is a placeholder that can change in value.

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So as an example, I could enter a password of Cisco.

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You might enter a different password in your topology that's going to be stored in this verbal that's

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then going to be sent to the router.

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At this point, now, the first thing the script needs to know is what a device are we going to telnet

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to?

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In this example, it's configured to Telnet to itself, and that's not what we want to do in this network.

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So one of the first things we need to do is configure the router with an IP address and a username and

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password so that the network automation container can telnet to the router and configure it.

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So I'll give the router a name of router one and then on gigabit zero zero I'll configure an IP address

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of 1921681 2271.

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Now the reason for doing that is the network automation container has been allocated to this IP address

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in this subnet by the net cloud.

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This is a slash 24 subnet.

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Network automation containers using this IP address once again.

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So I'll configure the router with an IP address in the same subnet and I'll shut the interface.

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So hopefully at this point the network automation container should be able to ping this IP address of

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the broader because the interface is now come up.

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And there you go.

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The network automation container can ping the router, but at this point won't be able to telnet to

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the router.

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Notice the connection is refused.

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Before you automate, make sure that things work manually.

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So in other words, you should first test that things work and then you can automate.

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So as an example, one of the things we want to configure here is a username and a password of, let's

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say, Cisco.

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In these initial examples, I'm not trying to do everything securely.

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I simply want to get you started.

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In programming, we have this concept of iteration.

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Start something, then iterate or improve your scripts as you go along.

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And I think that's a very important skill just to get started and then improve things as you go along.

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So in this example, I want to simply configure things so that you can see an example of network automation.

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In this example on the V lines, I'm going to use the command login local so that the script gets prompted

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for a username and password.

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And I'm going to say transport input all.

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Now, you could tie that down to S-H and Telnet.

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But because this is a lab, I'm not too worried about that.

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So let's try and telnet again.

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We can see that we prompted for our username and then our password.

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So exit out of the rudder on back on the network automation container.

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I'll save the router's configuration.

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So let's ed the script by using Nano.

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The IP address that we're going to connect to is 1921681 2271.

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In other words, it's the IP address of the router.

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We then going to prompt the user to enter their username?

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So rather than prompting them for this, let's ask them to enter their telnet username.

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So what should happen is the script should prompt the user for their telnet username and their password

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and then it will telnet to the router based on this available.

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So we configuring a variable here with the IP address of the router.

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We are hard coding values in the script.

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Now programmers with a lot of experience will tell you that you shouldn't.

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Hard code values.

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That's true.

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But again, we'll get to that later.

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For now, we simply want to get started automating the network so we're going to hard code or that value

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and then later on we'll improve the scripts.

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So the host of variable is configured with this value.

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After this point in the script and then at this point the Telnet library is being used to Telnet to

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the host that we specified over here.

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We are leveraging the Telnet library that someone else wrote in our script.

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So rather than us developing a low level Telnet program, we're going to simply leverage or reuse the

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code that's then going to be stored in this variable.

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And then we're doing something at this point.

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The script's going to wait until it sees a log in.

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And that's actually incorrect because when we telnet to the router and I'll just telnet locally, what

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it should look for is the username, so I'll copy that.

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And I'll edit this line because what we're looking for is username and not login.

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When the script sees a username, it's going to write.

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In other words, it's going to send.

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The username that the user entered at this point to the router.

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It's using ASCII encoding here and then it's going to follow that with a carriage return.

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So in other words, it's going to type your username.

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David Press Enter.

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That's logically what's happening in the background.

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Then the script says if a password was configured, in other words, we entered a password at this point.

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It's going to wait until it sees password.

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That's correct when telnet to a Cisco router.

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So when it sees that it's going to write the password that was entered here.

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So in other words, it's going to send the password to the router in ASCII format and press enter again,

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enter the username and then the password.

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And hopefully at that point we'll be logged into the router.

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Now here it's trying to write a Linux command to the router.

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That command is not supported on a Cisco router.

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What we want to do is type enable so that we can go to enable mode.

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At this point, no password has been set.

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So going back to the console of the router, we need to set or create an enable password.

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And again, I'll simply set it to Cisco.

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This is why it's important to test things, make sure that they work manually before you automate.

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So again.

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And to use a name and to password at this point then type enable.

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So enable press enter.

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Now we need to enter the enable password.

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So what I'm going to do is copy that line and paste it here.

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And I'll send a password of Cisco to the broader.

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Now again, you don't want to embed passwords in your scripts like this.

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Later on, we'll improve the script.

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But to get started will embed the password in the script.

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So we're going to enter a password of Cisco and that will take us to privilege mode or enable mode on

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the broader.

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Now, once we there, we want to do something.

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So as an example, we want to go to global configuration mode and then we want to create a loopback

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interface.

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So let's say loopback interface zero.

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And then we want to configure an IP address on the loopback interface, something like that.

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And then we want to exit.

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Or in our example, before we exit the Telnet session, we want to type end.

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So that we go back to privilege mode.

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And then we exit out of the Telnet session.

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So again when we telnet to the router username password enable password quantity interface loopback

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zero IP address creator the IP address.

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On the rudder type end and exit out of the rotor.

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That's the logic of what our script does.

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So I'm back on the console of the rudder.

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What I'll do is I'll remove the loopback interface.

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So show IP interface brief.

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Do that again.

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No loopback is currently configured on the router.