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Zorluk: OrtaUtilizing Command-Line Network Troubleshooting Utilities

A system administrator is troubleshooting an inability to establish a secure remote administration session via SSH to a Linux server located at 192.168.1.50192.168.1.50. The administrator executes the command `netstat -an` directly on the server to inspect active network socket states and receives the following truncated output:

Proto Local Address Foreign Address State
TCP 0.0.0.0:23 0.0.0.0:0 LISTENING
TCP 0.0.0.0:80 0.0.0.0:0 LISTENING
TCP 0.0.0.0:443 0.0.0.0:0 LISTENING

Based on the utility output, which condition explains why remote SSH connections to this server are failing?

  1. The SSH daemon is not running or is not bound to listen on standard TCP port 22.Cevap
  2. B
    The server is currently accepting SSH sessions on TCP port 23, indicating an active encrypted remote management service.
  3. C
    The command output demonstrates that local DNS client resolution has failed to map numerical socket addresses to human-readable hostnames.
  4. D
    The listening sockets indicate that an AAAA DNS resource record is missing for IPv4 interface binding.

Cevap

The SSH daemon is not running or is not bound to listen on standard TCP port 22.
Secure Shell (SSH) operates over TCP port 22 by default. In the provided `netstat -an` output, the server lists active listening services on TCP ports 23 (Telnet), 80 (HTTP), and 443 (HTTPS), but TCP port 22 is completely missing. This indicates the SSH daemon process is not running or is not listening on its default port, causing incoming connection attempts to fail.

Adım Adım Çözüm

1
Analyze the utility and parameters used
The `netstat -an` command displays all active network connections and listening ports (`-a`) using numerical IP addresses and port numbers (`-n`).
Numerical display prevents DNS lookup delays and shows exact port numbers being monitored.
2
Inspect listening TCP ports in the command output
The server has active listeners on TCP port 23 (Telnet), TCP port 80 (HTTP), and TCP port 443 (HTTPS).
To accept incoming connections for a protocol, a service daemon must be bound and listening on its designated port.
3
Evaluate incoming connection request requirements against active listeners
SSH relies on TCP port 22 by default. Since port 22 is absent from the LISTENING socket table, incoming SSH connection requests will be rejected by the TCP stack.
The SSH service process is either stopped or configured to use a non-standard port not shown in the listening table.

Anahtar Kavram

Port and protocol monitoring using netstat/ss utilities
Tahmini Süre:1m 30s
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Konular

Utilizing Command-Line Network Troubleshooting Utilities

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