TACACS+ is the correct choice because it provides centralized AAA with full encryption, encrypting the entire authentication payload—including the username, password, and all traffic between the client and server—while separating authentication, authorization, and accounting into distinct processes. This full-packet encryption ensures that credentials and session details remain protected during transit, meeting the requirement for a protocol that supports encrypted centralized management. On the CompTIA Network+ N10-009 exam, this question tests your ability to distinguish TACACS+ from RADIUS, which only encrypts the password and leaves other attributes in the clear; a common trap is choosing RADIUS for its broader use in network access, but TACACS+ is specifically designed for device administration with complete encryption. Remember the memory tip: TACACS+ encrypts the entire conversation, while RADIUS only hides the password.
N10-009 Network Operations Practice Question
This N10-009 practice question tests your understanding of network operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 network administrator needs to implement a solution that allows for centralized management of user authentication, authorization, and accounting for network device access. The solution must support encryption of the entire authentication process. Which protocol should be selected?
TACACS+ encrypts the entire authentication packet (username, password, etc.) and is commonly used for AAA on network devices (routers/switches).
B
RADIUS
Why wrong: RADIUS encrypts only the password field; the rest of the packet is sent in clear text. Although RADIUS can be used for device admin, it does not encrypt the entire authentication packet.
C
LDAP
Why wrong: LDAP is a directory access protocol, not an AAA protocol. It can be used for authentication but does not provide accounting or full packet encryption.
D
Kerberos
Why wrong: Kerberos is a ticket-based authentication protocol used in Windows domains. It is not typically used for AAA on network devices and does not provide accounting.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TACACS+
TACACS+ is the correct choice because it separates authentication, authorization, and accounting (AAA) into distinct processes and encrypts the entire authentication payload, including the username, password, and all other traffic between the client and the server. This full-packet encryption ensures that credentials and session details are protected during transit, meeting the requirement for centralized management with encrypted authentication.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
TACACS+
Why this is correct
TACACS+ encrypts the entire authentication packet (username, password, etc.) and is commonly used for AAA on network devices (routers/switches).
Related concept
Read the scenario before looking for a memorised answer.
✗
RADIUS
Why it's wrong here
RADIUS encrypts only the password field; the rest of the packet is sent in clear text. Although RADIUS can be used for device admin, it does not encrypt the entire authentication packet.
✗
LDAP
Why it's wrong here
LDAP is a directory access protocol, not an AAA protocol. It can be used for authentication but does not provide accounting or full packet encryption.
✗
Kerberos
Why it's wrong here
Kerberos is a ticket-based authentication protocol used in Windows domains. It is not typically used for AAA on network devices and does not provide accounting.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that RADIUS encrypts all traffic because it uses a shared secret, but the trap is that RADIUS only encrypts the password, not the entire packet, whereas TACACS+ encrypts the full authentication payload.
Detailed technical explanation
How to think about this question
TACACS+ uses TCP port 49 and encrypts the entire body of each packet (except the standard header) using a shared secret and MD5-based hashing, ensuring confidentiality for all AAA data. In contrast, RADIUS uses UDP (ports 1812/1813) and only encrypts the password field using a shared secret and MD5, leaving other attributes like username, service type, and accounting data exposed. A real-world scenario where this matters is when auditing network device logins: TACACS+ logs each command executed, while RADIUS typically only logs authentication events, making TACACS+ superior for detailed accounting and security compliance.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Operations — This question tests Network Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: TACACS+ — TACACS+ is the correct choice because it separates authentication, authorization, and accounting (AAA) into distinct processes and encrypts the entire authentication payload, including the username, password, and all other traffic between the client and the server. This full-packet encryption ensures that credentials and session details are protected during transit, meeting the requirement for centralized management with encrypted authentication.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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