350-601 Security Practice Question
An engineer is configuring 802.1X for network access control. Which AAA protocol should be used for communication between the authenticator (switch) and the authentication server?
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
✓
RADIUS
802.1X uses RADIUS for communication between the authenticator and the authentication server.
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 it's wrong here
TACACS+ is used for device administration, not 802.1X.
- ✓
RADIUS
Why this is correct
RADIUS is the standard protocol for 802.1X authentication.
- ✗
LDAP
Why it's wrong here
LDAP is for directory queries, not 802.1X.
- ✗
DIAMETER
Why it's wrong here
DIAMETER is an evolution of RADIUS but not commonly used in Cisco data center environments for 802.1X.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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