This LFCS practice question tests your understanding of networking. 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 Linux server cannot reach the internet, but internal LAN connectivity works. The output of 'ip route' shows a default gateway of 192.168.1.1, but pinging 8.8.8.8 fails. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The default gateway is not reachable or has no internet connectivity.
The gateway may be down or misconfigured.
The ARP table is corrupted.
Why wrong: ARP is for local LAN, not routing to external.
The default gateway is missing.
Why wrong: The route is present, so it's not missing.
DNS resolution is failing.
Why wrong: Pinging an IP does not require DNS.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The default gateway is not reachable or has no internet connectivity.
The default gateway 192.168.1.1 is present in the routing table, but pinging 8.8.8.8 fails while internal LAN connectivity works. This indicates that the gateway itself either cannot be reached (e.g., due to a layer 2 issue or misconfiguration) or, more likely, it has no upstream internet connectivity. Since the default route is configured, the failure is not due to a missing gateway but rather the gateway's inability to forward traffic to external networks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The default gateway is not reachable or has no internet connectivity.
Why this is correct
The gateway may be down or misconfigured.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The ARP table is corrupted.
Why it's wrong here
ARP is for local LAN, not routing to external.
The default gateway is missing.
Why it's wrong here
The route is present, so it's not missing.
DNS resolution is failing.
Why it's wrong here
Pinging an IP does not require DNS.
Common exam traps
The trap here is that candidates often assume a missing default gateway is the problem when they see internet failure, but the question explicitly states the default gateway is present, shifting the focus to the gateway's own connectivity rather than the local routing table.
Detailed technical explanation
When a packet is destined for an external IP (e.g., 8.8.8.8), the kernel performs a routing lookup and matches the default route, forwarding the packet to the next-hop gateway (192.168.1.1). The gateway must then have a route to the internet or be connected to an upstream router; if it lacks internet access or its own default route, it will drop the packet or return an ICMP unreachable. This scenario often occurs in virtualized environments where the host's NAT or bridge configuration is broken, or when the ISP link is down on the gateway device.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: The default gateway is not reachable or has no internet connectivity. — The default gateway 192.168.1.1 is present in the routing table, but pinging 8.8.8.8 fails while internal LAN connectivity works. This indicates that the gateway itself either cannot be reached (e.g., due to a layer 2 issue or misconfiguration) or, more likely, it has no upstream internet connectivity. Since the default route is configured, the failure is not due to a missing gateway but rather the gateway's inability to forward traffic to external networks.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.
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