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ISC2 CC Practice Question: A company's network uses 802.1X authentication…
A company's network uses 802.1X authentication for wired and wireless access. Which component authenticates the user credentials against an identity store?
⚠ Common exam trap
ISC2 often tests the misconception that the authenticator (switch or AP) performs authentication, but in 802.1X the authenticator only controls port access based on the RADIUS server's decision, not the credential validation itself.
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
✓
Authentication server (RADIUS)
In 802.1X, the authentication server (typically a RADIUS server) is the component that validates user credentials against an identity store such as LDAP, Active Directory, or a local database. The supplicant (client) provides credentials, the authenticator (switch or access point) relays EAP frames, but only the RADIUS server performs the actual authentication decision.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Supplicant
Why it's wrong here
The supplicant is the client software on the endpoint that supplies credentials to the authenticator; it never validates them against a directory. It is tempting because it initiates the 802.1X exchange, but authentication against an identity store is performed by the authentication server, typically RADIUS.
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Authenticator
Why it's wrong here
The authenticator is the switch or access point that relays EAP exchanges; it forwards credentials to the authentication server rather than validating them against the identity store. It is tempting because it enforces port access, but the authentication server performs the actual credential check.
- ✓
Authentication server (RADIUS)
Why this is correct
The RADIUS authentication server receives the credentials forwarded by the authenticator and validates them against the identity store, returning accept or reject. The supplicant supplies credentials and the switch or access point merely relays them, so the server performs authentication.
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Access point
Why it's wrong here
An access point acts as the authenticator, relaying EAP frames between supplicant and authentication server; it does not itself check credentials against an identity store. It is tempting because it enforces port-based access control, but the RADIUS server performs the actual credential validation.
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.
Go deeper
Related to this question
Learn chapter
Authentication and Authorization Methods
Key term
User
A user is any person, system, or device that interacts with an IT service, resource, or identity system, typically authenticated through credentials and authorized to perform specific actions.
Key term
Extensible Authentication Protocol
Extensible Authentication Protocol (EAP) is a flexible authentication framework used in network access control, particularly in wireless and point-to-point connections, that supports multiple authentication methods without requiring changes to the underlying protocol.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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