CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 engineer is configuring 802.1X authentication for wired network access. The authentication server supports EAP-TLS. What must be deployed to clients to support this authentication method?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Client certificate
EAP-TLS requires mutual authentication using digital certificates on both the client and the server. The client must present a certificate to prove its identity to the authentication server, which is validated against a trusted root CA. Without a client certificate, EAP-TLS cannot establish the TLS tunnel, as it relies on certificate-based client authentication per RFC 5216.
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.
✓
Client certificate
Why this is correct
EAP-TLS requires both client and server certificates for mutual authentication.
Related concept
Read the scenario before looking for a memorised answer.
✗
Server certificate
Why it's wrong here
Server certificate is required for the authentication server, but the client also needs a certificate for EAP-TLS.
✗
RADIUS server
Why it's wrong here
The RADIUS server is the authentication server itself, not a client requirement.
✗
Shared secret
Why it's wrong here
Shared secrets are used in EAP-MD5 or PEAP, not in EAP-TLS which uses certificates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the distinction between what is deployed to clients versus the infrastructure; candidates mistakenly choose 'server certificate' because they know TLS requires certificates, but forget that EAP-TLS mandates client certificates for mutual authentication.
Detailed technical explanation
How to think about this question
EAP-TLS operates by establishing a TLS tunnel between the client and the authentication server; the client sends its certificate inside the EAP-Response/TLS message, and the server validates it against a trusted CA certificate store. If the client certificate is missing or untrusted, the server sends an EAP-TLS fatal alert and authentication fails. In enterprise deployments, client certificates are often provisioned via PKI with SCEP or manual enrollment, and the switch acts as an authenticator using RADIUS (RFC 2865) to proxy EAP frames.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Client certificate — EAP-TLS requires mutual authentication using digital certificates on both the client and the server. The client must present a certificate to prove its identity to the authentication server, which is validated against a trusted root CA. Without a client certificate, EAP-TLS cannot establish the TLS tunnel, as it relies on certificate-based client authentication per RFC 5216.
What should I do if I get this CISSP 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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