What's changed: Initial version
6.3Controller APIs and interpreting REST responses
Covers Catalyst Center's Intent API and SD-WAN Manager (vManage)'s REST API as a flow from token acquisition to the actual call, then teaches deciding what to do next (retry, fix credentials, fix the URL, or wait) from the returned status code—200/201/204, 400/401/403/404/429, and 5xx—together with the payload.
What burns the most time in controller-API automation is misreading the returned code and trying to fix the wrong thing. Rewriting the URL over and over when a 401 came back, or retrying instantly on a 429 and jamming things further—both stem from failing to read where the code says responsibility lies. Broadly, status codes signal a division of responsibility: 2xx = success, 4xx = the caller's (client's) problem, 5xx = the server's problem. Using the real controllers Catalyst Center and SD-WAN Manager, this section follows the full arc of obtaining an auth token -> making the call -> interpreting the response -> choosing the next action.
6.3.1The shape of a controller API call
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