7.5. REST APIs
đź’ˇ First Principle: REST APIs use HTTP methods (the same protocol as web browsing) to interact with resources. Think of them as a standardized language for applications to talk to network devices. Instead of screen-scraping CLI output, you get structured data with a guaranteed format.
Consider this comparison: A monitoring tool needs interface statistics from 500 switches. Without an API: SSH to each device, run show interface, parse the text output—hoping Cisco doesn't change the format in the next IOS version. One format change breaks everything. With an API: send GET /interfaces, receive structured JSON. The API is a contract; CLI output is whatever the vendor felt like printing.
What happens when you rely on CLI parsing: Your Python script parses show ip route output using regular expressions. It works perfectly—until an IOS upgrade slightly changes the spacing. Now your script fails on half your devices. APIs return JSON with defined fields; they don't break because someone added a space.
Why this matters: APIs aren't just "nice to have" for automation—they're the foundation. Scripts that configure devices, dashboards that visualize network health, integrations between tools—all depend on APIs. If you understand REST, you can work with any modern network platform. So what makes REST different from other approaches? It's the combination of standard HTTP methods and predictable resource URLs that makes it universally applicable.