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So friends, why don't we talk about the real big dog in time when it comes to

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network automation

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and this is Ansible.

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Now Ansible is by far at least at this point in time as of this recording.

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It is by far the most popular network automation utility on the planet.

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Now you may be thinking, well if it's so popular there must be a good reason

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why it's so popular

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and this is basically true. Let's talk a little bit about it. So first thing to

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state about Ansible

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is that when it comes to automation it is an agentless solution. So this is
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is that when it comes to automation it is an agentless solution. So this is

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very good when it comes

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to managing older devices. So these Cisco devices which I have in this little

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diagram right here

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these are all running Cisco iOS and this is a rather old operating system. It

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was not designed

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with automation in mind and they do not have the ability to install an agent.

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Now if you happen

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to have some real world experience in the world of network engineering then you

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know

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you don't just get to go and replace an entire infrastructure just because a
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you don't just get to go and replace an entire infrastructure just because a

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new model of device

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has came out. You very often may walk into a network where by most of the

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devices are 10 years old

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or 15 years old or maybe even 20 years old or more. Network engineering can

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really be kind of a

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dire circumstance at times. So this is just the nature of the networks that we

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have to administer.

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Now we don't want to have to be hamstrung by these old technologies and be told

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that you know

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what there is no automation available for you. If you've got an old machine, if
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what there is no automation available for you. If you've got an old machine, if

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you've got an old

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network, well you're just stuck with doing old copy paste stuff and just doing

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some regular CLI

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jockeying on the command line. Now here is the important part with respect to

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Ansible. It does not

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matter how old these devices are because essentially Ansible is just going to

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be installed on the

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machine that is going to manage these devices. This is going to be our Ansible

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Control node okay.

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So the Ansible Control node will be installed here and so long as that device

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can actually connect
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can actually connect

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to the devices that we want to manage, then we can use Ansible to ultimately

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push out these

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automated configurations to the target devices. So this simple fact of Ansible

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being agentless and

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not requiring these new fancy modern devices in order to use Ansible. This is

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one of the reasons why

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it's so popular within network automation. Like I said, we do have many of

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these old devices still

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in play but that is not all. When it comes to automation generally, well it

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kind of has a bit of an

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intimidation factor. If you're told you know you have to really be good at the
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intimidation factor. If you're told you know you have to really be good at the

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Python program in

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language in order to do any type of automation, it kind of puts people off and

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this is just natural.

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If you're just used to working with OSPF and BGP and creating VLANs that type

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of thing and then suddenly

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you have to go out and learn a programming language. This is not so enticing to

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say the least. Now here

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is the trick. Ansible is actually written in Python. However, the cool thing is

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is that in order to

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use Ansible, you actually do not need to know how to write any Python. Quite
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use Ansible, you actually do not need to know how to write any Python. Quite

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simply, you just

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utilize what is known as YAML files, which is just a file format that has a

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great emphasis on human

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readability and USEN user, you just write your instructions, utilizing YAML and

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under the hood,

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Ansible will translate those commands into Python and then begin connecting to

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all of our devices

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and assuring out all of the automation. So let's just briefly describe some of

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the components

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that make up Ansible. So the very first component is one known as the inventory
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that make up Ansible. So the very first component is one known as the inventory

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. This is so, so

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crucial to how Ansible actually operates. Think about it like this. When you

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want to automate a

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network in order to be able to connect to the devices in that network, you

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essentially have to

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describe the network. You want to tell the automation system which devices you

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have. So say, for

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example, take these four devices here. This could be my little network. I would

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want Ansible to know

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about them. And the way I do this is by specifying their details within my Ans
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about them. And the way I do this is by specifying their details within my Ans

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ible inventory. So Ansible

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has this one little file that looks into and reads in all the information. So

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what kind of information

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am I talking about? Well, what about the login username for each device, as

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well as the login

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password? What about the connection details of that device? What is its actual

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IP address or

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what's its domain name? How do I reach this particular device in the network?

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Which type of device

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are we actually talking to? Is this a Cisco iOS device? Or maybe this is a Jun

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iper device? Because

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ultimately, the different devices actually have a different way of being
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ultimately, the different devices actually have a different way of being

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managed. Because these

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devices are managed in different ways. They've got different modes. They've got

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different syntax,

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so on, so forth. If we're going to automate these devices, we need to be very

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explicit about what

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the device actually is. So all this information here is going to be written in

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our inventory

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file. And once again, this can be specified in YAML format, but it can also be

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specified in a

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format known as INI, as we get to see. Basically, you can select the file
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format known as INI, as we get to see. Basically, you can select the file

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format that you want for

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this particular component of Ansible. And just choose which one you find

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easiest depending on the

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situation. You might prefer one over the other. For small and simple networks,

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I prefer to use the

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INI format, but for inventories whereby the topology is a little bit more

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complex, I then choose

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to switch to the YAML format, but it's entirely up to you. Now, the cool thing

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about our inventory is

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that we can actually have this logical segmentation of our devices. What on

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earth am I talking about
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earth am I talking about

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here? So once again, let's look at this four node network. Now, let's just

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imagine that, say, for

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example, the top two devices, they happen to be in the United States. This is

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the physical location,

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okay? So these are in the USA. And let's just say the bottom two devices are in

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the UK. Now, let's

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suppose we wanted Ansible to automate out a very particular configuration for a

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very particular

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subset of devices. By virtue of us having these groups within our inventories,

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we can target those
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we can target those

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groups based on that group membership or rather target those devices based on

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their group membership.

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Let me give you a more concrete example. Let's imagine we wanted to configure

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some type of

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NTP server. Now, we didn't want every device in our network to have the exact

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same configuration.

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Instead, we wanted people in the USA to get a very particular NTP configuration

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. And people in the

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UK to get a very different NTP configuration. But because this inventory allows

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for this logical
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for this logical

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grouping of our devices, we can just say, hey, Ansible, connect all devices in

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the USA and give it an

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NTP server of 1.1.1.1.1.1, for example. So now Ansible goes, hey, devices in

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the USA group are S1 and S2.

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So I will just connect to those devices only and configure them with this

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particular server.

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And then similarly, we could say, hey, you know what, we would like also to

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have an NTP server

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configuration this time of let's go with 2.2.2.2. And this should be applied to
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configuration this time of let's go with 2.2.2.2. And this should be applied to

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every single device that we

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have in the UK. So then Ansible can say, hey, in the UK, devices S3 and S4 are

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a member of that group.

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So I will now connect to these two devices and give them the configuration of 2

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.2.2.2 for NTP. Now,

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obviously, and a network is smaller this. This might be a little bit trivial.

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But you can imagine

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if in the USA group, what if we happen to have 1000 devices? We wouldn't want

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to continue

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the login and login and login for every device to make that change instead. If
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the login and login and login for every device to make that change instead. If

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we can just place

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all devices in the USA group, all 1000 of them, then we can just tell Ansible

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to go, hey, you know what,

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go and make that change to that group and all those devices will be targeted

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precisely no matter

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how many of them there are. So this really makes configuration management way,

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way, way easier.

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And this is just one of the benefits we get with Ansible. So pretty much the

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inventory specifies

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which devices we have under our control, how to connect to them and how to

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essentially group

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them together. Now, in the example that I just specified before, say, for
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them together. Now, in the example that I just specified before, say, for

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example, we want to push

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out some type of NTP configuration. This is actually the task that we want Ans

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ible to do. Now,

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this is specified in what is known as an Ansible Playbook. Now, first thing to

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state about Ansible

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Playbooks, these are always written in Yamal. Okay, so we do not have an

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alternative file format.

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We can't write these in I and I always, always, always going to be Yamal style.

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Now, quite simply,

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these playbooks are used in conjunction with our inventory. The playbook allows
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these playbooks are used in conjunction with our inventory. The playbook allows

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us to specify

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what to be want to happen such as an NTP configuration or maybe an OSPF update.

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That type of thing.

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All of this specifies within the playbook. And then within the actual playbook

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itself,

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we specify which part of the inventory do we want to target with this

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particular task. So,

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quite simply, if we imagine we have two file right here, okay, this one can be

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our inventory file,

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this one can be our playbook file. Let's imagine in the inventory, we've got a

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little group called

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USA and it's got devices S1 and S2 and we've got a group called UK, which compr
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USA and it's got devices S1 and S2 and we've got a group called UK, which compr

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ises of devices S3

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and S4. Well, inside the playbook, we can say, hey, we want to target the USA

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group within the

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inventory and then we want to do some NTP stuff such as configure 1.1.1.1.1. So

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, Ansible reads this

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information, configures NTP, the target the USA group, looks into the inventory

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and say, hey, I should

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be connecting to devices S1 and S2 and now those configs go to those two

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devices. Now, obviously,

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these two drawings are greatly simplified. Examples of a playbook as well as an
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these two drawings are greatly simplified. Examples of a playbook as well as an

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inventory file will get

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to see what both of those look like very, very shortly, but ultimately, this is

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what we're talking

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about. Now, there are some more components with respect to Ansible things such

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as templates,

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things such as variables, but for the moment, just remember that Ansible is

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going to be utilising

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an agentless solution whereby the targets do not have to have anything

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installed on them to be

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managed by Ansible. And because of this, Ansible is going to utilise the push

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model, it's going to

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make great use of YAML files very particularly with respect to playbooks and
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make great use of YAML files very particularly with respect to playbooks and

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ultimately, playbooks allow us

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to specify what we want to happen in the network and the inventory file allows

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us to specify which

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devices we want the automation to happen to. So now we have some of the basic

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components of Ansible

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under our belt. Let's then talk about that inventory file in a little bit more

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detail as well as

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Ansible's main configuration file.