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    Question

    A network administrator is troubleshooting a problem

    where a web application is not reachable. After confirming that the physical connections are intact, the administrator pings the application server successfully, but the HTTP service is still unavailable. At which OSI layer is the problem most likely located?
    A Physical Layer Correct Answer Incorrect Answer
    B Data Link Layer Correct Answer Incorrect Answer
    C Network Layer Correct Answer Incorrect Answer
    D Transport Layer Correct Answer Incorrect Answer
    E Application Layer Correct Answer Incorrect Answer

    Solution

    The problem is most likely at the Application Layer, as the HTTP service (port 80 or 443) is associated with this layer. The successful ping indicates that the lower layers (Physical, Data Link, Network, and Transport) are functioning correctly. The ping verifies connectivity at the Network Layer, and the presence of the transport connection (TCP/UDP) implies no issues at the Transport Layer. 1. The Application Layer ensures protocols like HTTP, SMTP, and FTP are operational. 2. A failure at this layer suggests a misconfiguration or malfunction in the web server software or application itself. 3. This problem could include incorrect server configurations, missing HTTP services, or software bugs affecting application-level communication. Why Other Options Are Incorrect: • A) Physical Layer: A failure at this layer would result in no network connectivity, and ping would fail. • B) Data Link Layer: Responsible for node-to-node data transfer. Ping success indicates no issues here. • C) Network Layer: Handles IP addressing and routing. Successful ping confirms this layer is functional. • D) Transport Layer: Ensures data delivery. Issues here would prevent ping replies, which is not the case.

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