Network Automation with Ansible

Chapter 5. How Ansible Works

After looking at what Ansible can offer from a network automation perspective, we’ll now take a look at how Ansible works. You will learn about the overall communication flow from an Ansible control host to the nodes that are being automated. First, we review how Ansible works out of the box, and we then take a look at how Ansible, and more specifically Ansible modules, work when network devices are being automated.

Out of the Box

By now, you should understand that Ansible is an automation platform. In fact, it is a lightweight automation platform that is installed on a single server or on every administrator’s laptop within an organization. You decide. Ansible is easily installed using utilities such as pip, apt, and yum on Linux-based machines.

Note

The machine that Ansible is installed on is referred to as the control host through the remainder of this report.

The control host will perform all automation tasks that are defined in an Ansible playbook (don’t worry; we’ll cover playbooks and other Ansible terms soon enough). The important piece for now is to understand that a playbook is simply a set of automation tasks and instructions that gets executed on a given number of hosts.

When a playbook is created, you also need to define which hosts you want to automate. The mapping between the playbook and the hosts to automate happens by using what is known as an Ansible inventory file. This was already shown in an earlier example, but here is another ...