Building an Ansible network inventory

In this recipe, we will outline how to build and structure the Ansible inventory to describe the network setup outlined in the previous section.

Getting ready

Make sure that Ansible is already installed on the control machine.

How to do it...

1. Create a new directory with the following name: ch2_ios.
2. Inside this new folder, create the hosts file with the following content:

$ cat hosts
 [access]
 access01 Ansible_host=172.20.1.18
 access02 Ansible_host=172.20.1.19

[core]
 core01 Ansible_host=172.20.1.20
 core02 Ansible_host=172.20.1.21

[wan]
 wan01 Ansible_host=172.20.1.22
 wan02 Ansible_host=172.20.1.23

[lan:children]
 access
 core

[network:children]
 lan
 wan

3. Create the Ansible.cfg file with the following content:

$ cat Ansible.cfg

[defaults]
 inventory=hosts
 retry_files_enabled=False
 gathering=explicit

How it works...

We built the Ansible inventory using the hosts file, and we defined multiple groups in order to group the different devices in our topology in the following manner:

• We created the access group, which has both access switches (access01 and access02) in our topology.
• We created the core group, which groups all core switches that will act as the L3 termination for all the VLANs on the access switches.
• We created the wan group, which groups all our Cisco IOS–XE routes, which will act as our wan routers.
• We created another group called lan, which groups both access and core groups.
• We created the network group, which groups both lan and wan groups.

Finally, we created the Ansible.cfg file and configured it to point to our hosts file to be used as an Ansible inventory file. We disabled the setup module, which is not required when running Ansible against network nodes.