350-501 Automation and Assurance Practice Question
An automation engineer uses RESTCONF to configure a Cisco ASR 9000 router. When sending a PATCH request to update an interface description, the API returns 404 Not Found. What is the most probable issue?
⚠ Common exam trap
Cisco often tests the distinction between HTTP status codes (404 vs 401 vs 501) to see if candidates understand that a 404 specifically points to a missing resource, not an authentication or module support issue.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The interface does not exist on the device.
A 404 Not Found response to a RESTCONF PATCH request targeting a specific interface indicates that the resource (the interface) does not exist at the given URI. RESTCONF uses the URI path to identify the exact YANG data node; if the interface name in the URI does not match any configured interface on the Cisco ASR 9000, the server returns 404. This is consistent with RFC 8040, where 404 is used when the target resource cannot be found.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HTTP authentication is required.
Why it's wrong here
Authentication is required but if missing, the response would be 401, not 404.
- ✗
The YANG module is not supported.
Why it's wrong here
If the YANG module were unsupported, the device might return 501 Not Implemented or a data model error, not 404.
- ✓
The interface does not exist on the device.
Why this is correct
A non-existent interface results in a 404 because the resource URI points to a path that does not exist.
- ✗
The RESTCONF username/password is incorrect.
Why it's wrong here
Incorrect credentials would return 401 Unauthorized.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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