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- [Instructor] Learning to code

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and work with programmable infrastructures

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is extremely important
in today's environment.

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You saw the value of using
APIs in previous lessons.

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You also saw the capabilities
of SDN solutions,

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and the benefits of an SDN solution.

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So whether you actually have configured

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a large network in the past

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or you're just getting started,

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you know that this is actually,

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probably, a very challenging task, right?

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It involve a lot of clicking
around in GUIs, or typing,

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or copy and pasting, and
many repetitive tasks.

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So nowadays, network infrastructure
devices and components

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are enabled to support APIs

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and many programmability capabilities

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to complete powerful task

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and reduce all that repetitive work,

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and save you a lot of time.

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So using APIs, you can
actually make requests,

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like the ones that I'm
actually showing in here,

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to get a status of an interface,

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or get information about the
last change that, you know,

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that interface was actually changed,

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or actually applying different
configuration changes

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like shutting down the interface,

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or shutting down an interface
on a thousand devices

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at the same time, or enabling an interface

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on a thousand devices at
the same times, right?

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So it allows you to really
scale across the organizations.

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Now, many modern programming languages,

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like Python, and Go, and
things like JavaScript,

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and Swift, and many others,

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are flexible and easier to
learn than their predecessors.

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Especially Python, right?

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A lot of times, you know,
I get this question,

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"Should I actually learn
a programming language

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to get into security?"

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"Should I learn a programming language

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to get into networking?"

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And my answer is, "Absolutely."

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I always suggest to start with Python.

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Python is one of the programming languages

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recommended first to learn,

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not only because of
network programmability,

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but many other scenarios.

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And it's actually one of
the languages that are used

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for many different things,
from just a quick script,

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to automation, to data science,
machine learning, and so on.

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There are many different sites

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that allow you to get started.

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And here, I'm actually
showing you a few resources.

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And I also have, in my GitHub repository,

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a lot of different references

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that allow you to actually
get started with Python.

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This training is not a Python
class, and it's not gonna,

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you know, walk you through
how to actually learn Python,

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or Go, or Swift, or JavaScript.

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But, you know, what
I'm doing is, actually,

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I'm putting as much information possible

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in the GitHub repositories
that we have available for you,

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that if you're not exposed to
these programming languages,

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you can actually get started.

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Now, combining programming
capabilities with developer tools

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like get or Git, or GitHub,
and GitLab repositories,

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and also package management
system and virtual environments,

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it actually allows you to create

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your own set of very
powerful tools and workflow.

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And later, you're gonna
learn more about, actually,

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you know, RESTful APIs.

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We're gonna go over a
brief introduction of Git,

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and interpreting basic Python scripts

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used to call different
security appliances.

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And you're gonna learn,
also, about pxGrid,

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which is a solution that
you can take advantage of

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to integrate many different capabilities

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with devices like the Cisco ISE,

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the identity service engine.

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Now, another amazing thing
is the power of code reuse

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and online communities, right?

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In the past, if you actually
wanted to create some program,

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you always have to start from scratch.

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But nowadays, you can actually collaborate

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and use a lot of open
source and a lot of modules,

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like I was talking about Python.

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So you can take advantage of
tons and tons of Python modules

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that allows you not only to
perform some very quick tasks,

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but they're Python modules that are used

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for network programmability as well.

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For example, here I'm
actually showing the package

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called requests.

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It is a Python package that is installed

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using a package manager for
Python called pip, right?

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And if you're not familiar with pip,

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I actually have a reference here for you.

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And basically, the requests
library allows you to make

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HTTP and HTTP requests in
Python in very, very easy way.

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And the reason that I'm mentioning this

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is because Python
requests and that package

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is actually used a lot nowadays,

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whenever we interact with APIs.

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So later, whenever we're
gonna be introducing APIs

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and introducing different Python scripts

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to call security appliances

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and other devices in the network,

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the requests package in
Python or the module,

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it actually is used fairly often.

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And, you know, it will be good for you

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to at least become
familiar with this package.

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For example, here, I'm actually just using

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the interactive Python shell interpreter

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to import the requests package,

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and then send an HTTP
GET request to a website.

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In this case, it's actually h4cker.org.

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And the HTTP request
is actually successful,

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and that's why you see the
200 message response below.

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Now, the W3Schools website
has a very good explanation

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of the HTTP status code messages, right?

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So I mentioned to you
the 200 message response.

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But I want to actually, at least,

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summarize all the response
here for your benefit

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and for your reference.

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The messages in the 100
range are informational.

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The 200 range are related
to successful transactions,

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and that's what you actually want to get

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whenever you interact with
any HTTP or HTTPS device.

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And especially whenever you're interacting

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with APIs as well, right?

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So we want to get, you know,
the status code message 200.

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Now, in the 300 range,

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that's actually related
to HTTP redirection.

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So if you actually visit a website

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and it redirects you to another
one, you might get something

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like an HTTP status code of 302, right?

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And you also have the
messages in the 400 range,

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and those are related to client errors.

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And the 500 range, those are
related to server errors.

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Now, I'm spending a
little bit of time here

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explaining a lot of the HTTP
protocol underlying functions.

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And the reason for that is
because you need to know

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or have an understanding

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of these functions and functionality

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in order to be successful interpreting,

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and also interacting, with APIs.

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And for, of course, network
programmability, right?

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Whenever HTTP servers and browsers

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communicate to each other,

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they perform interactions
based on headers,

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as well as body content.

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Now, the HTTP request,

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and in HTTP, there's an
HTTP request from the client

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and a response from the server.

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But in the request, it actually
has a different structure.

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You have the method,

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which is how that request
will actually be sent

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to the server and the entities, you know?

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So things like, for
example, GET. A GET request.

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And actually, that's used
to retrieve information

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from the server.

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HEAD is basically the same as GET,

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but it actually returns
only the HTTP headers

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and no document body from the server.

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You also have POST, which
actually sends data to the server,

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typically using HTML forms,
API requests, and the like.

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Now, you also have TRACE to
do a message loop-back test

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along the path to the target resource.

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You also have PUT

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to upload a representation
of the specified URI.

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DELETE, which deletes the
specified resource options,

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which actually is
returning the HTTP methods

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that the server supports.

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And CONNECT, which converts
the request connection

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to a transparent TCP/IP tunnel.

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And as I mentioned to you,

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the server after receiving this request

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generates a response, right?

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And the server response has
three digit status codes

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that are a brief,
human-readable interpretation

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of the status code.

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And those are the ones that
I explained to you earlier.