Which of the following is causing the connectivity issue?

A Linux administrator is troubleshooting SSH connection issues from one of the workstations.

When users attempt to log in from the workstation to a server with the IP address 104.21.75.76, they receive the following message:

The administrator reviews the information below:

Which of the following is causing the connectivity issue?
A . The workstation has the wrong IP settings.
B . The sshd service is disabled.
C . The server’s firewall is preventing connections from being made.
D . The server has an incorrect default gateway configuration.

View Answer

Answer: C

Explanation:

The server’s firewall is preventing connections from being made, which is causing the connectivity issue. The output of iptables -L -n shows that the firewall is blocking all incoming traffic on port 22, which is the default port for SSH. The output of ssh -v user@104.21.75.76 shows that the connection is refused by the server. To resolve the issue, the administrator needs to allow port 22 on the firewall. The other options are incorrect because they are not supported by the outputs. The workstation has the correct IP settings, as shown by the output of ip addr show. The sshd service is enabled and running, as shown by the output of systemct1 status sshd. The server has the correct default gateway configuration, as shown by the output of ip route show.

Reference: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, pages 406-407.