Quick Answer
The answer is `ip route show`. This command is the correct choice because it displays the kernel routing table, and the default gateway appears as a default route entry (typically shown as `default via 10.0.1.1 dev eth0`). When a server is reachable internally but not from the internet, a missing or incorrect default gateway is the most likely cause, and `ip route show` directly verifies whether that default route exists. On the Linux Foundation Certified System Administrator LFCS exam, this question tests your ability to troubleshoot network connectivity using modern `ip` commands rather than the deprecated `route` or `netstat -rn`. A common trap is reaching for `ping` or `traceroute` first, but those only test connectivity, not the routing table itself. To remember: think of the default gateway as the "exit door" for traffic leaving your network—`ip route show` checks if that door is actually configured.
This LFCS practice question tests your understanding of networking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 notices that a web server is not reachable from the internet but is reachable from the internal network. The server's IP is 10.0.1.10/24, and the gateway is 10.0.1.1. Which command should be used to verify the default gateway configuration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
arp -a
Why wrong: This shows the ARP cache, not routing information.
ip route show
This command displays the routing table, including the default gateway.
ip addr show
Why wrong: This shows IP addresses, not the routing table.
ss -tln
Why wrong: This shows listening TCP ports, not routing.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ip route show
The `ip route show` command displays the kernel routing table, including the default gateway entry. Since the server is reachable internally but not from the internet, a missing or incorrect default gateway is the likely cause. This command directly verifies whether a default route (e.g., via 10.0.1.1) is present.
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.
arp -a
Why it's wrong here
This shows the ARP cache, not routing information.
ip route show
Why this is correct
This command displays the routing table, including the default gateway.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
ip addr show
Why it's wrong here
This shows IP addresses, not the routing table.
ss -tln
Why it's wrong here
This shows listening TCP ports, not routing.
Common exam traps
The trap here is that candidates often confuse `ip addr show` (which shows IP configuration) with `ip route show` (which shows routing), leading them to check the IP address instead of the default gateway when troubleshooting external connectivity.
Trap categories for this question
Command / output trap
This shows the ARP cache, not routing information.
Detailed technical explanation
The Linux kernel uses the routing table to determine the next hop for outbound packets; a default route (0.0.0.0/0 via gateway) is essential for reaching external networks. The `ip route` command from the iproute2 suite replaces the older `route -n` and provides detailed routing information, including metrics and scope. In a scenario where the gateway is misconfigured or missing, packets destined for the internet are dropped because no route matches.
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: ip route show — The `ip route show` command displays the kernel routing table, including the default gateway entry. Since the server is reachable internally but not from the internet, a missing or incorrect default gateway is the likely cause. This command directly verifies whether a default route (e.g., via 10.0.1.1) is present.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A server has two network interfaces: eth0 (10.0.1.10/24, gateway 10.0.1.1) and eth1 (192.168.1.10/24, no gateway). Both are up. The default gateway is set to 10.0.1.1. A ping to 8.8.8.8 fails, but ping to 10.0.1.1 succeeds. What is the most likely cause?
hardWhy B: The default gateway is correctly set to 10.0.1.1, and ping to that gateway succeeds, so eth0 and its route are functional. However, ping to 8.8.8.8 fails, which indicates that the default route (0.0.0.0/0 via 10.0.1.1) is either missing or misconfigured, preventing traffic destined for external networks from being forwarded. The fact that eth1 has no gateway is irrelevant because the default route is already defined via eth0.
Variation 2. A host with this routing table can ping 10.0.2.1 but cannot ping 8.8.8.8. What is the most likely cause?
hardWhy B: The host can ping 10.0.2.1, which is on the directly connected 10.0.2.0/24 network, confirming that the local interface and link-layer are functional. However, it cannot ping 8.8.8.8, a public internet address. The routing table shows a default route via 10.0.1.1, so the host will forward the packet to that gateway. Since the host has a default route, the most likely cause is that the gateway 10.0.1.1 itself lacks internet connectivity (e.g., no upstream route, NAT misconfiguration, or ISP outage), preventing the packet from reaching 8.8.8.8.
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Last reviewed: Jun 11, 2026
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