300-320 Question #127: Real Exam Question with Answer & Explanation

The correct answer is A: Layer 2 mode. This describes the Cisco NAC Appliance Server operating in Layer 2 in-band mode. In Layer 2 mode the NAS sits inline (physically and logically) between the client and the rest of the network, so all traffic must pass through it. Because it operates at Layer 2, it can only see MAC

Question

At a certain customer's site, a NAS is both physically and logically in the traffic path. The NAS identifies clients solely based on their MAC addresses. In which access mode has this NAS been configured to operate?

Options

ALayer 2 mode
BLayer 3 Edge mode
CLayer 3 Central mode
DLayer 3 In-Band mode

Explanation

This describes the Cisco NAC Appliance Server operating in Layer 2 in-band mode. In Layer 2 mode the NAS sits inline (physically and logically) between the client and the rest of the network, so all traffic must pass through it. Because it operates at Layer 2, it can only see MAC addresses - it has no IP routing context to track clients by IP subnet. Layer 3 Edge and Layer 3 Central modes place the NAS at the Layer 3 boundary or use out-of-band placement where clients are identified by IP address, not MAC address.

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