Quick Answer
The correct HTTP header is Authorization: Basic YWRtaW46c2VjcmV0. This is because HTTP Basic Authentication requires the credentials to be formatted as a single string of username:password, which is then encoded using Base64 and prefixed with the word "Basic" in the Authorization header. The string YWRtaW46c2VjcmV0 decodes directly to admin:secret, making it the only option that follows the protocol correctly. On the Cisco DevNet Associate 200-901 exam, this concept tests your understanding of REST API authentication fundamentals, often appearing in questions about constructing raw HTTP requests or debugging API calls. A common trap is forgetting that the credentials must be colon-separated before encoding, or confusing Base64 with encryption—it is not secure, just a simple encoding. To remember the format, think "colon, encode, Basic space": you always start with username:password, then Base64 it, then write Authorization: Basic followed by that encoded string.
This 200-901 practice question tests your understanding of software development and design. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer is working with a REST API that uses HTTP Basic Authentication. The developer needs to send a request with the username 'admin' and password 'secret'. Which HTTP header should be set?
Authorization: Basic admin:secret
Why wrong: Incorrect: The credentials must be base64-encoded.
Authorization: YWRtaW46c2VjcmV0
Why wrong: Incorrect: The 'Basic' keyword is missing.
Authorization: Basic YWRtaW46c2VjcmV0
Correct: This is the standard format for Basic Auth.
Authorization: Bearer YWRtaW46c2VjcmV0
Why wrong: Incorrect: Bearer is for token-based auth.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Authorization: Basic YWRtaW46c2VjcmV0
HTTP Basic Authentication requires the credentials to be formatted as 'username:password', then Base64-encoded, and sent in the Authorization header with the 'Basic' scheme. Option C correctly includes the 'Basic' scheme followed by the Base64-encoded string 'YWRtaW46c2VjcmV0' (which decodes to 'admin:secret').
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Authorization: Basic admin:secret
Why it's wrong here
Incorrect: The credentials must be base64-encoded.
Authorization: YWRtaW46c2VjcmV0
Why it's wrong here
Incorrect: The 'Basic' keyword is missing.
Authorization: Basic YWRtaW46c2VjcmV0
Why this is correct
Correct: This is the standard format for Basic Auth.
Related concept
Read the scenario before looking for a memorised answer.
Authorization: Bearer YWRtaW46c2VjcmV0
Why it's wrong here
Incorrect: Bearer is for token-based auth.
Common exam traps
Cisco often tests whether candidates know that the credentials must be Base64-encoded and prefixed with the 'Basic' scheme, not sent in plaintext or with the wrong scheme like 'Bearer'.
Trap categories for this question
Keyword trap
Incorrect: The 'Basic' keyword is missing.
Detailed technical explanation
Under the hood, the Base64 encoding in Basic Authentication is not encryption—it is merely a transport encoding to safely transmit binary data over text-based protocols. The server decodes the Base64 string back to 'admin:secret' and validates the credentials. In real-world scenarios, Basic Authentication should always be used over HTTPS to prevent credentials from being easily intercepted, as Base64 can be decoded instantly by anyone who captures the header.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
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FAQ
Software Development and Design — This question tests Software Development and Design — Read the scenario before looking for a memorised answer..
The correct answer is: Authorization: Basic YWRtaW46c2VjcmV0 — HTTP Basic Authentication requires the credentials to be formatted as 'username:password', then Base64-encoded, and sent in the Authorization header with the 'Basic' scheme. Option C correctly includes the 'Basic' scheme followed by the Base64-encoded string 'YWRtaW46c2VjcmV0' (which decodes to 'admin:secret').
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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