Quick Answer
The correct answer is EAP over LAN (EAPoL). This is the protocol used directly between the client (supplicant) and the switch (authenticator) in an 802.1X wired authentication setup because EAPoL encapsulates Extensible Authentication Protocol (EAP) frames inside standard Ethernet frames, allowing the supplicant to transmit credentials to the authenticator before any network access is granted. On the Cisco SCOR / CCNP Security Core 350-701 exam, this distinction is critical: many candidates mistakenly think the client talks directly to the RADIUS server, but in reality, the authenticator relays EAP messages to the server via RADIUS, while the client-to-switch link remains EAPoL. A common trap is confusing EAPoL with EAP over RADIUS—remember that EAPoL is the local link protocol, and RADIUS is the backend transport. Memory tip: think "LAN = Local link" for EAPoL, and "RADIUS = Remote server" to keep the two separate.
This 350-701 practice question tests your understanding of network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 administrator is configuring 802.1X authentication on Cisco switches for wired endpoints. Which protocol is used between the client (supplicant) and the switch (authenticator)?
RADIUS
Why wrong: RADIUS is used between the authenticator and the authentication server.
EAP over UDP
Why wrong: EAP over UDP is not a standard protocol for 802.1X on wired networks.
EAP over LAN (EAPoL)
EAPoL is the standard protocol for 802.1X between client and switch.
TACACS+
Why wrong: TACACS+ is typically used for device administration, not for 802.1X.
Answer choices
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Common exam traps
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.
Detailed technical explanation
EAPoL operates at Layer 2 using EtherType 0x888E, and the switch uses the PAE (Port Access Entity) to manage the port state (unauthorized/authorized). A subtle behavior is that the switch can cache EAPoL frames to avoid re-authentication on every reconnection, but this is disabled by default for security. In real-world deployments, if the switch does not receive EAPoL-Start from the client, it may use MAC authentication bypass (MAB) as a fallback, which is a common scenario in mixed environments.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
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FAQ
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
The correct answer is: 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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