easyMultiple ChoiceObjective-mapped
350-701 Practice Question: A network administrator is configuring 802.1X…
A network administrator is configuring 802.1X authentication on Cisco switches for wired endpoints. Which protocol is used between the client (supplicant) and the switch (authenticator)?
⚠ Common exam trap
Cisco often tests the distinction between the protocol used on the client-to-switch link (EAPoL) versus the protocol used on the switch-to-server link (RADIUS), causing candidates to mistakenly select RADIUS or TACACS+ because they are more familiar with AAA protocols.
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
✓
EAP over LAN (EAPoL)
In 802.1X authentication, the client (supplicant) communicates with the switch (authenticator) using EAP over LAN (EAPoL), which is defined in IEEE 802.1X-2004. EAPoL encapsulates EAP frames in Ethernet frames, allowing the supplicant to send authentication credentials to the authenticator before granting network access. The authenticator then relays these EAP messages to the authentication server (typically a RADIUS server) using RADIUS, but the direct protocol between client and switch is EAPoL.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RADIUS
Why it's wrong here
RADIUS is used between the authenticator and the authentication server.
- ✗
EAP over UDP
Why it's wrong here
EAP over UDP is not a standard protocol for 802.1X on wired networks.
- ✓
EAP over LAN (EAPoL)
Why this is correct
EAPoL is the standard protocol for 802.1X between client and switch.
- ✗
TACACS+
Why it's wrong here
TACACS+ is typically used for device administration, not 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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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