CV0-004 Troubleshooting Practice Question
Network Topology
Refer to the exhibit. A cloud engineer is troubleshooting network connectivity to a server with IP 10.0.0.5. The server is on the same subnet. Based on the iptables rules shown, what is the most likely cause of the connectivity failure?
⚠ Common exam trap
The trap here is that candidates often overlook the INPUT chain's destination match and assume the FORWARD chain is responsible for same-subnet traffic, or they misinterpret a zero packet count as an inactive rule, when in fact the rule is simply waiting for matching traffic.
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 INPUT chain drops all traffic destined to the 10.0.0.0/8 network
The INPUT chain has a rule that drops all traffic destined to the 10.0.0.0/8 network, which includes the target server at 10.0.0.5. Since the server is on the same subnet, traffic to it must traverse the INPUT chain on the local system, and this DROP rule will match and discard packets before any other rule can accept them. The rule's position and destination match make it the most direct cause of the connectivity failure.
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 FORWARD chain policy drops all traffic
Why it's wrong here
Incorrect; FORWARD chain policy is ACCEPT, and the rule drops all, but the issue is INPUT.
- ✗
The OUTPUT chain rejects all traffic to the server
Why it's wrong here
Incorrect; OUTPUT chain accepts all.
- ✗
The DROP rule in INPUT has zero packet count, so it is not effective
Why it's wrong here
Incorrect; zero count means no packets have matched yet, but the rule is still in effect.
- ✓
The INPUT chain drops all traffic destined to the 10.0.0.0/8 network
Why this is correct
Correct; the DROP rule in INPUT blocks traffic to 10.0.0.0/8.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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