The script successfully requests an authentication token in the first block but fails to include that token in the second request (requests.get). In Cisco DNA Center APIs, the /dna/system/api/v1/auth/token endpoint returns a service ticket. This ticket must be included in the headers of subsequent API calls (like the device list request) using the key X-Auth-Token. The 401 Unauthorized error occurs because the headers variable used in the requests.get call only contains the Content-Type, leaving the request unauthenticated. Adding the acquired token to the header resolves the issue.

Option A is incorrect: The URL /dna/intent/api/v1/network-device is the correct and official endpoint for retrieving the network device list in Cisco DNA Center.

Option B is incorrect: An HTTP 401 error is an authentication failure, not a network layer issue. If there were reachability issues, the script would return a connection timeout or "No route to host."

Option D is incorrect: The 401 error occurs during the second request (device list), not the first. The first request (authentication) likely succeeded since the script proceeded to the next block.

Cisco DevNet Documentation: Cisco DNA Center REST API Guide - Authentication. (Specifies that the token must be passed in the X-Auth-Token header for all subsequent calls).

Cisco DNA Center Platform Documentation: Intent API Reference - Get Device List. (Validates the endpoint URL used in the exhibit).

RFC 7235: Hypertext Transfer Protocol (HTTP/1.1): Authentication. Section 3.1: 401 Unauthorized. (Defines the 401 status code as a lack of valid authentication credentials).

Cisco Learning Network: Programming for Cisco DNA Center (NPDEV). (Provides code patterns for multi-step REST API interactions requiring token persistence).