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Difficulty: HardUtilizing Command-Line Network Troubleshooting Utilities

A network technician is troubleshooting an issue where remote users cannot reach an internal web server at IP address 192.168.10.45192.168.10.45 over a secure connection. The technician executes a diagnostic utility directly on the server to inspect network socket states, receiving the following output:

$ ss -tuln
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
tcp LISTEN 0 128 0.0.0.0:80 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:67 0.0.0.0:*

Based on the command output above, which of the following best explains why client HTTPS requests to `https://192.168.10.45` are failing?

  1. The web server daemon is not currently running or bound to listen on TCP port 443.Answer
  2. B
    HTTPS requires UDP transport protocols, but the output indicates only UDP port 67 is bound.
  3. C
    The server's local resolver returned a non-authoritative response, preventing port 443 socket activation.
  4. D
    The network interface lacks an AAAA record, preventing IPv4 socket binding for encrypted web traffic.

Answer

The web server daemon is not currently running or bound to listen on TCP port 443.
The `ss` (socket statistics) command with `-tuln` flags displays listening TCP and UDP sockets with numeric port formatting. Standard HTTPS traffic relies on TCP port 443. In the provided terminal output, only TCP ports 22 (SSH) and 80 (HTTP) are listed under the `LISTEN` state. Because TCP port 443 is missing from the list, the web server daemon is either stopped, misconfigured, or not bound to port 443.

Step-by-Step Solution

1
Analyze the CLI utility command flags
The `ss -tuln` command queries socket statistics for TCP (`-t`), UDP (`-u`), listening sockets (`-l`), using numeric port numbers (`-n`).
Understanding command switches ensures accurate output parsing.
2
Examine the active listening sockets in the terminal snippet
Identified TCP port 22 (SSH), TCP port 80 (HTTP), and UDP port 67 (DHCP server).
Pinpoints which transport protocols and port numbers are actively accepting incoming connections.
3
Correlate missing socket listeners with the reported failure symptom
HTTPS traffic requires an active listener on TCP port 443. Because port 443 does not appear in the listening state list, incoming HTTPS connection requests cannot complete a TCP 3-way handshake.
Identifies the root cause of connection failures.

Key Concept

Socket State Analysis using Command-Line Utilities
Estimated Time:2m 0s
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Topics

Utilizing Command-Line Network Troubleshooting Utilities

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