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So friends, in the previous video we had just configured our Ansible Config

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uration file

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as well as our Ansible Inventory. What we now want to do is to visit the

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concept of variables.

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So with respect to automation, machines can quite easily invoke repetition.

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Say for example, we wanted all of our devices to have an NTP server of 8.8.8.8.

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Now if that were the case for every single device, well, that would be a really

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easy problem

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for the automation solution to solve. It would just connect to all of these

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devices

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and just type the exact same commands in the case of Cisco iOS syntax.
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and just type the exact same commands in the case of Cisco iOS syntax.

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If I go to one of my devices here, all Ansible would have to do would be to

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type the command

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enable and then type the command configr terminal and then NTP server and then

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the value of the server

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itself, which in this case here would be 8.8.8.8. These exact commands would

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have no variation,

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no matter which device we connected to. But as we know in the real world, this

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is not

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quite a reality. Very often, instead, you're going to have different
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quite a reality. Very often, instead, you're going to have different

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configurations on different devices.

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Quite simply, there is going to be some type of variation in the actual value

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that you're passing in.

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Classical example, let's say we were using automation to configure IP

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addressing,

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but the IP addresses on this device are going to be different from the IP

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address on this one,

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as well as the IP address of this and this. So the way we solve for this in the

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world of automation

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is to make use of variable values. So let me tell you how we solve it. Let's
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is to make use of variable values. So let me tell you how we solve it. Let's

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say once again,

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to use the same example, we want to effectively push out some NTP configuration

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. What we want to do

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here is we want to identify which part of the configurations actually will vary

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and which parts

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will be static. Well, in our network, all four devices happen to be Cisco

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devices. So this part

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here is going to stay the same regardless of which device. Ansible this part,

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as well, this

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particular portion right here, NTP space server, however, the actual value we
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particular portion right here, NTP space server, however, the actual value we

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populate in here,

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this can be variable. It might change depending on the device. We're connecting

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to it might

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want a different IP address, for example. Whereas the syntax before it, this is

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always going to stay the same.

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So let's maybe say one device, we get NTP server 8.8.8.8 and another one was

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going to get NTP server 2.2.2.2.2,

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the only part that is varying is this little portion here. So essentially, we

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want to reference

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these values and associate them with our devices. And then we can have Ansible
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these values and associate them with our devices. And then we can have Ansible

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substitute these values

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in at the correct part of the configuration. Now, just to be clear here, with

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respect to Ansible,

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we have the concept of a group variable and we also have the concept of a host

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variable. Now,

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this is really, really useful for pushing out configurations, because let's

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maybe say we want to have,

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you know, as we specified in our USA group, let's imagine like we said before,

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they're going to have

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the NTP server configuration of 1.1.1.1. Whereas in the UK, they're going to

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have the NTP server

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configuration of 2.2.2.2. Here's how we'll solve this. Within our Ansible
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configuration of 2.2.2.2. Here's how we'll solve this. Within our Ansible

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directory structure,

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we're going to have particular files named after each group. So we'll have a

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file in my case here

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called USA.Yaml, as well as one called UK.Yaml. Okay. Now, all we will do in

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both of these files is to

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reference in name of a variable and associate it with a particular value. So

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what that means is that

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when Ansible is connecting to the devices in the USA, it's going to use the

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value in this particular
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value in this particular

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file for the configuration. Whereas when Ansible is connecting to devices in

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the UK group, i.e. these

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two devices, when we go to make that configuration, Ansible simple looks at the

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value in this particular

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file and substitutes that in upon configuration. So quite easily, we can now

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automate out slight

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differences across these groups. So that devices in the USA can get custom

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configurations as can

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devices in the UK and not just that. Let's just say, for example, we want to

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add in more devices

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into the UK. So let's imagine we've got devices 5 and 6 year ago. Now, if we
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into the UK. So let's imagine we've got devices 5 and 6 year ago. Now, if we

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specify that they belong

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to the UK group, then if we happen to push NTP configurations to these devices,

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then Ansible is

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going to give them the values that we specify within that UK.Yaml file. But

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remember what I just

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said, we also have host variables as well. Now host variables actually override

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the group membership

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variables. So let's say, for example, that we generally want everyone in the UK

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to have an NTP

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server configuration of 2.2.2.2. So we specify that in our UK.Yaml file.
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server configuration of 2.2.2.2. So we specify that in our UK.Yaml file.

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However, let's say for whatever

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reason, we would like S5 to have a different configuration. Let's maybe say

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that's going to get 2.2.2.2.3

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for whatever reason. What we would do with the quickly host variable file named

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after it's let's

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call this S5.Yaml. And instead of this particular file, we would specify the

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different value 2.2.2.2.3.

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So because of this, if we happen to connect the devices in the USA, they can be

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configured with

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1.1.1.1.1. That applies to both of those devices right here. Whereas in the UK,
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1.1.1.1.1. That applies to both of those devices right here. Whereas in the UK,

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all devices are going

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to get the configuration of 2.2.2.2 except ones which have the same value redef

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ined in their host variables,

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which is what we see in this case here of device number five, which gets the

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slightly modified

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value of 2.2.2.2.3. So this might be a little bit confusing at first. So the

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best thing to do is to

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write some variables and then we can see things in action. So let's go back to

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our terminal right here.

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And what I'm going to do is I'm going to create a directory, let's just say MK
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And what I'm going to do is I'm going to create a directory, let's just say MK

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DR to make a new directory.

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And I'm going to create a directory called groupVars as well as a directory

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called hostVars. Now this

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happens to be an Ansible Convention. Ansible will automatically look for these

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particular directories

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and seek to suck in the files with themal directories. Now inside, if I go and

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change into the group

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Vars directory, what I will do is I will create a file for every single group

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that I have in my inventory.

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So I've got a group called Cisco. So I'll create a file called Cisco.Yaml. I've
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So I've got a group called Cisco. So I'll create a file called Cisco.Yaml. I've

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got a group called

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USA. So I'll create one USA.Yaml and I've got a group called UK. So I'll have

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one called UK.Yaml.

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Now similarly, if I go into the hostVars folder, remember in my inventory, I've

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got four different

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hosts. What I will similarly do is create a host file for every single host. I

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'll say touch S1.Yaml.

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Touch S2.Yaml. Touch S3.Yaml and then finally create one for S4 as well.
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Touch S2.Yaml. Touch S3.Yaml and then finally create one for S4 as well.

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Now as for our variables, because our Cisco devices all have the same

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configurations with respect to

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the login details, I'm going to define those values in there. And because of

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those four devices,

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membership within the inventory, Ansible will seek to use these connection

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details when talking to

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those devices. So what I will do is go and open these up. So let's go into the

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group Vars folder

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and I'll go into Cisco.Yaml. Now there are some special variable names that Ans

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ible will seek to

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use. One is known as Ansible_User. This is how we can define our login user
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use. One is known as Ansible_User. This is how we can define our login user

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name. So for all

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devices, everyone that belongs to the Cisco group, we have a login user name of

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Admin. And similarly,

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we've got a special keyword called Ansible_Password, whereby we specify the

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password. All four devices

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all have the same login password of AdminPass. Now specify my Ansible network

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OS that again,

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another specialized keyword. This tells Ansible which type of device we're

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talking to. So in this

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case here, if I say Cisco.ioes.ioes, this is Ansible_Speak for basically the
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case here, if I say Cisco.ioes.ioes, this is Ansible_Speak for basically the

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same for connecting to an

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old school Cisco CLI device. And I'll tell Ansible the type of connection that

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's going to be Ansible.NET

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commem.network CLI. Pretty much we're going to be using the regular CLI. So

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these variables will be

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associated with all devices in the Cisco group, which as we can see are all

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four of our devices.

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And for my configuration, let's go with my NTP configuration. Let's open this

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up. Let's now go

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into group Vars once again and we'll go into the USA group. So let's just

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follow the same convention.
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follow the same convention.

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Now in my case here, I can call my variable anything I so wish. It's going to

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be a custom variable

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that I have created. So let's just call this NTP_config and all I will do now

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is I will associate a value. So

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in the USA, I want everyone to get the configuration of 1.1.1.1.1. So I'll just

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pop that in there. Whereas

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if you happen to be in the UK, let's open your, what I want to do is to use the

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exact same key. So let's

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just copy this. So we reference the same thing. I'll paste this in and all I
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just copy this. So we reference the same thing. I'll paste this in and all I

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will do is I'll change

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the corresponding value. So UK1 will get 2.2.2.2 as we can see right here. Now

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like I say, if I so wish,

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if I wanted to override the group membership configuration for any of my

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devices, then what I could do

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is specify the same key at the host variable level. Let's maybe say S2 should

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have a very particular

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configuration what I could do is therefore go in to the host Vars directly this

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time. So going to

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here and going to S2. Once again, I'm going to use the exact same key NTP_con
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here and going to S2. Once again, I'm going to use the exact same key NTP_con

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fig and this time we

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could give it a different configuration entirely. So let's maybe go with 8.8.8.

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8.8. So quite simply,

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when Ansible goes to executes, if we attempt to push out configurations related

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to NTP,

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well, the bottom two devices should get their values from their UK membership,

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which I believe is

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an NTP configuration of 2.2.2.2. And in the case here, we've got two devices in

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the USA group. So we'll

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look into the USA file to get that value. And that's going to be 1.1.1.1.1.
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look into the USA file to get that value. And that's going to be 1.1.1.1.1.

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However, before Ansible

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executes, it's going to notice that for this particular device, there is a more

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specific value

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in its host variable file and it's not going to use this value, it will

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therefore use the value of

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8.8.8.8 for this one device specifically. So now we have our configuration file

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or inventory as

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well as our variables configured. Let's now put it all together by pushing

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configurations to our

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devices utilizing Ansible.