- In this video, we're
going to discuss JSON, or JavaScript Object Notation. This is something that you
need to know for the exam. So make sure that you watch this video and that you understand JSON. (upbeat dance music)` Okay, so let's start with why. You've probably seen one of these before. Are you a human or robot? Now the reason we have captchas is because machines struggle
with unformatted data. If the data isn't clear, machines will struggle
to interpret the data. JSON is a way to format the data. It's also a way to send data
from one machine to another. We, as humans, can
interpret data quite easily, especially if it's slightly off. So as an example, if you type show version on a Cisco IOS device,
so let's say classic IOS, the output will be different
to a Cisco IOS XE device, which is different to
a Cisco Nexus device. The output will vary slightly. Now that's not a problem for us as humans. We can make adjustments
for the slight changes in the output of the data, but
machines struggle with that. So we want data that is
consistently formatted properly so that machines can communicate properly. As an example, if I SSH
to a switch using Python, so I connect to the switch using Python and type show IP route or show version. If I'm not using a JSON format, so the output is not
formatted in JSON format, or another format such as XML or YAML, it's difficult to write code that can interpret the data properly. Now Cisco, once again, have
made things easier using pyATS. So if you use pyATS rather than, say Netmiko, to connect it directly to a device using a Python script, the output comes back in a format that's easy to interpret
using a Python script. But if you're using pure Netmiko or pure Telnet and you're simply typing show version and you're trying to pass that output, it's very difficult to write good Python code to pass the output, number one, and secondly, to handle a situation
when the output changes. So you upgrade the router, as an example, and the output formatting is different. Your Python code will
struggle to interpret that. So, for machine to machine communication it makes a sense to use standard output, and it makes sense to have a format that's easy to interpret,
especially for machines. So to help us with JSON formatting, let's start with a Tesla. Okay, I'm gonna ask you some questions about this Tesla. Well, first question is
who's the manufacturer? That would be Tesla. What type of model is this? Model X. Notice how I've formatted this data. Manufacturer: Tesla. This is known as a key, and
this is known as a value. So we've got a key value pair. What is the model? It's Model X. Color white. Fuel electric. Miles per gallon city 99. Miles per gallon highway 93. I've simply pulled this
information off Google, hopefully it's correct. But don't get hung up about the data. Look at the format of the data. Again, we have what's called a key separated by a colon,
and then we have a value. You need to understand JSON formatting. That's an example of JSON formatting. It actually looks like this. We have to use double inverted commas. So it would be something like firstname colon, then
David, as an example. So JSON data is written
as name value pairs. So going back here, I said key. It could be also referred to as name. So, name value pair. Another example is lastname. And a value. Name value pair consists of a field in double quotes followed by a colon, followed by a value. Make sure you understand that format. Now, for the exam there are two JSON data types that you need to
know, objects and arrays. Let's start with an object. So, a JSON object would
look something like this. Notice we've got curly braces. Data is surrounded by curly braces and it's an unordered
collection of key value pairs. So here's our key. Firstname: David, lastname: Bombal. Notice separated by a comma. Make sure that you know the format. So, curly braces surrounds the data. We've got key value. The keys and values use double
quotes not single quotes. Each key value pair is
separated by a comma, except the last one. Trailing commas must not be used. Now it's going to be easier to look at it in this format, easier to read. Spaces are not important with JSON. So notice the curly braces First key first value. Second key second value,
separated by a comma. Comma third key, third value. No comma. So if you put a comma here
that would be a problem. Make sure, once again, that you recognize this format for the exam. So, just to summarize, a JSON object is an unordered collection
of key value pairs. In other words, this is not ordered. It could be in any order, doesn't matter. Surrounded by curly braces, once again. Key and value pairs are
separated by a colon, spaces don't matter. But make sure that the last
one doesn't have a comma. Use double quotes not single quotes. That's all very good and well, me showing you the stuff with PowerPoint, but let me show you this practically. You'll be able to download
this PowerPoint presentation so that you have access to the details. But I want to show you this practically because it's going to be a lot easier to demonstrate this on a live Cisco device rather than just showing you the stuff with PowerPoint. Now the great thing is that DevNet have a Nexus always on sandbox. You can simply SSH to the sandbox and you'll be able to try commands, which I'm going to show you right now. Now on a Mac I'm going
to use this command, but on Windows you could use Putty, as an example, to connect. Okay, so I'm going to copy this. Open up a terminal. I'll make this big to
make sure that it's clear. And I'm going to paste that command in. So basically I'm SSHing to port 8181, using this username and this
is the DNS name of the router. I have to put my password
in, which is admin_1234! or bang if you prefer. So, there's the password. There's the user name. This is the port. This is the protocol we need to use, and this is the domain name. Okay, it's complaining about my password, let's try that again. Okay, so I've successfully logged in to this Nexus box, hosted by Cisco DevNet. Cisco DevNet have made
things so much easier because you can practice this stuff, you can try things using their free labs. Now on a Windows computer
you could use Putty, and SSH to port 8181. So SSH. Hostname is sbx-nxos-mgmt.cisco.com. And I can click open. You have to accept the public key, so I'm going to say yes. Login as admin. Admin_1234! or bang. And there you go. I've logged in. So, show version. This command shows me that
this is a Nexus device. We can see various
information about the device. We can see it's a 9000v
Chassis, as an example. So I'm going to jump back to
my Mac and do this on my Mac. Show version on the Mac will show the same kind of information. Now we can use standard
commands like show int vlan 100. And that shows us standard information like we would get on any
other type of device. So we can see, as an example, DEMO PLEASE DON'T TOUCH
IP address is this. But what we could do is
we can send that to JSON. So, let's just use JSON, and we get to the JSON information like that, but it's not very easy to read. So let's use json-pretty. So json-pretty. There's our information. So show int vlan 100. We see the JSON formatting. Notice the curly braces. We've got information about
this interface Vlan100. Important to note, key, value, separated by a colon then a comma, key, value again, comma at the end, double inverted commas. Very important. The last entry doesn't
have a comma at the end. Data is contained within curly braces. So this data has these curly braces. TABLE_interface has these curly braces. And then we've got the all
encompassing curly braces,. So that's an example, practically, of JSON formatting versus show interface vlan 100. Standard command. This is a format that we
as humans would understand, but this is a format that a machine will understand much better. So just remember, we want
to have standard formatting for machines. As an example, sh ip int brief here gives us a list of
interfaces on the device. That's human readable format. But if we say json-pretty, this gives us the information
in JSON formatting. Sh ip int brief | json-pretty. Notice there's a big difference here, we have the square brackets. So ROW_intf, square
bracket, scrolling down. Now the link may be quite slow here. My internet connection to the
DevNet site is quite slow, but notice here is the
next square bracket. Here we've got data within curly braces. Again, notice no comma at the end here, but this has curly braces
and a comma at the end. The data within here is key value comma. Now the reason why we have square brackets is because we are using
what's called an array. In this slide I've kind of summarized it. Notice the curly braces. Here we've got square brackets. And inside here we've got
an ordered list of values. The reason why we want this is because we've got multiple interfaces. So we've got interface Vlan100. And then here we've got interface Vlan200, and information about those interfaces. So rather than just showing information about one interface, so a single object, we've now got an array of interfaces that we're looking at. So an array in JSON is an
ordered list of values. Uses square brackets. It can store all kinds of data. So, it could store things such as strings. A string is like a sentence,
hello, or a word, hello. Whereas a number is something
like 1 or 2 or 2.123. Values must be separated
by commas, once again. So, notice once again that an object doesn't have those square brackets. This is the output for
show version | json-pretty. Important here, comma. Comma. No comma. We've got the key value
pair separated by a colon. Make sure that you know this formatting. I have said that enough times now I think. So here's an example, once again, of show interface Vlan100. Again you can download this PowerPoint slides so that you have
all this information. I've given you a few examples of that. But again, it's much easier
to see this practically. And I'm going to take
this to the next level now by showing you how to run
Python on this Nexus box and do stuff in Python, and
then I'm going to show you how to access the box
remotely using a Python script that I'm going to run on my local computer and then pull out
similar JSON information. (upbeat dance music)
