CAS-004 Security Architecture Practice Question
A security administrator needs to ensure that only authorized devices can access the corporate network. Which technology would best enforce this requirement at the network access layer?
⚠ Common exam trap
CAS-005 often tests network access control by offering VPN or TLS as options. Candidates may confuse remote access security with local network access control, but 802.1X is specifically for authenticating devices at the network edge.
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
✓
802.1X
802.1X is an IEEE standard for port-based network access control (NAC) that authenticates devices before granting access to the network. It ensures that only authorized devices can connect to a switch port or wireless access point, enforcing access control at the network access layer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TLS 1.3
Why it's wrong here
TLS 1.3 encrypts and authenticates data in transit between endpoints, but it does not evaluate device identity or posture before granting network access. It is tempting because it provides mutual authentication, which suits protecting specific client-server channels rather than controlling which devices may join the network.
- ✗
IPsec VPN
Why it's wrong here
IPsec VPN secures traffic between established endpoints but does not assess device identity or compliance before granting network access. It is tempting because it authenticates peers and is the right choice for encrypting site-to-site or remote-access tunnels, not for admission decisions at the access layer.
- ✓
802.1X
Why this is correct
802.1X performs port-based network access control, requiring devices to authenticate via EAP before gaining Layer 2 connectivity. This enforces the requirement that only authorised devices reach the corporate network, blocking rogue hardware at the access layer.
- ✗
DNSSEC
Why it's wrong here
DNSSEC cryptographically signs DNS records to prevent spoofing and cache poisoning; it performs no device authentication or authorisation. It is tempting because it hardens a foundational network service, and would be correct when the requirement is verifying DNS response integrity rather than controlling network admission.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CAS-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-005 exam.