The answer is to run `ufw allow out 22/tcp`, which permits outbound SSH traffic on port 22. This is correct because the server can ping and resolve hostnames, confirming that basic network connectivity and DNS are functional, but the active UFW firewall is blocking outbound TCP port 22, causing the "Connection timed out" error. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of UFW’s default outbound policy, which often denies all outgoing traffic unless explicitly allowed. A common trap is to mistakenly focus on inbound rules or to use `ufw allow 22` without specifying the direction, which only opens port 22 for incoming connections. Remember the memory tip: "Outbound, outbound, out the door—specify 'out' for SSH to the remote shore."
XK0-005 Troubleshooting Practice Question
This XK0-005 practice question tests your understanding of troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A system administrator is troubleshooting a server running Ubuntu 20.04 that cannot establish outbound SSH connections. The server can ping external IP addresses and resolve hostnames. The administrator tries `ssh user@remotehost` and gets 'Connection timed out'. The firewall (ufw) is active. Which step should be taken?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Allow output traffic on port 22 with ufw allow out 22/tcp.
The server can ping external IPs and resolve hostnames, so networking and DNS are working. The issue is that outbound SSH traffic on port 22 is being blocked by the active UFW firewall. The correct step is to allow outbound TCP traffic on port 22 using `ufw allow out 22/tcp`, which permits the client to initiate SSH connections to remote hosts.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Check the SSH client configuration in /etc/ssh/ssh_config.
Why it's wrong here
Client configuration issues typically cause different errors, not timeouts.
✗
Restart the networking service.
Why it's wrong here
Networking is already functional (ping and DNS work); restarting won't help.
✓
Allow output traffic on port 22 with ufw allow out 22/tcp.
Why this is correct
Explicitly allowing outbound SSH traffic resolves the timeout while maintaining security.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable the firewall with ufw disable.
Why it's wrong here
Disabling the entire firewall is not a targeted solution and weakens security.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume SSH issues are always server-side (e.g., checking SSH server config or restarting services) and overlook that the local firewall's outbound policy can block client-initiated connections even when inbound rules are correctly configured.
Detailed technical explanation
How to think about this question
UFW (Uncomplicated Firewall) defaults to a deny-outbound policy on many Ubuntu installations, meaning all outbound traffic is blocked unless explicitly allowed. The `ufw allow out 22/tcp` command inserts an iptables rule in the OUTPUT chain that permits TCP segments with destination port 22. In real-world scenarios, administrators often forget that outbound rules are also needed for client-initiated connections, not just inbound rules for servers.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Allow output traffic on port 22 with ufw allow out 22/tcp. — The server can ping external IPs and resolve hostnames, so networking and DNS are working. The issue is that outbound SSH traffic on port 22 is being blocked by the active UFW firewall. The correct step is to allow outbound TCP traffic on port 22 using `ufw allow out 22/tcp`, which permits the client to initiate SSH connections to remote hosts.
What should I do if I get this XK0-005 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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