In PPP (Point-to-Point Protocol) authentication, if the authentication fails, the authenticator sends an Authenticate-Reject message.

Option A (Incorrect - Authenticate-Ack): Sent when authentication is successful.

Option B (Incorrect - Authenticate-Reply): Not a valid PPP authentication message.

Option C (Correct - Authenticate-Reject): Sent when authentication fails, and the connection is rejected.

Option D (Incorrect - Authenticate-Nak): Used for PPP negotiation, not authentication failure.

Thus, the correct answer is C.

To help Fit APs locate an AC (Access Controller), the DHCP server must provide the AC IP address using DHCP Option 43.

Option 55 (Incorrect): Used to request a list of DHCP options.

Option 82 (Incorrect): Used for Relay Agent Information, not AC discovery.

Option 10 (Incorrect): Not relevant for APs or CAPWAP.

Option 43 (Correct): This option delivers the AC IP address to Fit APs so they can establish a CAPWAP tunnel.

Thus, the correct answer is D.

Comprehensive and Detailed In-Depth Explanation:

MAC Address Table Analysis:

5489-9885-18a8 → Learned on Eth0/0/2

5489-989d-1d30 → Learned on Eth0/0/1

Switch Behavior:

If a frame arrives on the same port where the destination MAC is learned, it is discarded to prevent loops.

Since the frame arrives on Eth0/0/2, and the MAC is already associated with Eth0/0/2, the switch discards the frame.

A broadcast address, with all host bits set to 1, is used for broadcasting messages to all devices within a network segment. It cannot be assigned to a specific host, as its purpose is to reach every device in the subnet. Therefore, it is reserved for broadcast communication and cannot serve as an individual host address​.

Comprehensive and Detailed In-Depth Explanation:

Address Resolution Protocol (ARP) is used to map an IP address to a MAC address in IPv4 networks. When a device needs to communicate with another device in the same subnet, it uses ARP to find the corresponding MAC address.

ARP sends a broadcast request on the network asking " Who has IP X.X.X.X? Tell me your MAC address. "

The device with the matching IP replies with its MAC address, which is then stored in the ARP cache.

Detailed Explanation:In a Layer 2 WLAN, an Access Controller (AC) typically handles authentication and management but does not act as a gateway. Instead, a Layer 3 device, such as a router, serves as the gateway. (Reference: HCIA-WLAN Training Material, WLAN Layer 2 and Layer 3 Concepts)

In STP, a port moves from Learning to Forwarding state after the Forward Delay timer has expired. This delay ensures stability by allowing time for the topology to converge before the port begins forwarding user traffic, thereby preventing loops in the network during the transition​.