Chapter 3: Building Configuration Templates Using Jinja2

Configurations are the lifeblood of networking devices and could be, to draw a relation to software engineering, regarded as the source code of a network. When writing such configuration files, it can be handy to build templates that parts can be reused from. In this chapter, we will see how we can programmatically build and render such templates using a templating language called Jinja2.

The applications of this are manifold. Think of a script that reaches out to your IP Address Management (IPAM) system and automatically builds a configuration based on the information and the template you have written. Using sub-templates, you can significantly improve the overall cohesiveness of your configurations. Instead of each network engineer writing their own take on some type of configuration, you can pull in a template that does exactly this configuration for you.

While we could build our configuration templates with pure Python...