CV0-004 Troubleshooting Practice Question
Exhibit
iptables -L -v -n
Chain INPUT (policy ACCEPT)
pkts bytes target prot opt in out source destination
0 0 DROP tcp -- eth0 * 0.0.0.0/0 10.0.1.10 tcp dpt:22
5 600 ACCEPT tcp -- eth0 * 10.0.0.0/16 10.0.1.10 tcp dpt:22Refer to the exhibit. An administrator is unable to SSH into a cloud server with IP 10.0.1.10 from a remote location (outside the 10.0.0.0/16 network). What is the most likely cause?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The firewall rule order is incorrect
Firewall rules are evaluated in order; the first rule (rule #1) drops all SSH traffic from any source, and the second rule (rule #2) permits SSH traffic only from the internal network (10.0.0.0/16). Since the remote location is outside this network, the packet matches the first rule and is dropped before reaching the second rule. Option B is incorrect because the firewall is not dropping all packets on port 22; it only drops those from external sources due to the rule order. Option C is incorrect because a host key change would cause a different SSH warning, not a connection timeout. Option D is incorrect because if the SSH service were not running, the error would be 'connection refused' rather than a timeout.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The firewall rule order is incorrect
Why this is correct
The drop rule appears before the allow rule, so external traffic is dropped before reaching the allow rule.
- ✗
The firewall is dropping all packets on port 22
Why it's wrong here
The second rule accepts SSH from internal network, so not all packets are dropped.
- ✗
The SSH host key has changed
Why it's wrong here
A changed host key would cause a warning, not a connection failure.
- ✗
The SSH service is not running
Why it's wrong here
The SSH service might be running but blocked by firewall.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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