LFCS Networking Practice Question
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?
⚠ Common exam trap
Many exam-takers 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.
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 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.
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 default gateway is not reachable or has no internet connectivity.
Why this is correct
LAN connectivity proves the interface and local routing work, while a failed ping to 8.8.8.8 indicates the default route's next hop cannot forward traffic. The gateway at 192.168.1.1 is either unreachable or lacks upstream internet connectivity.
- ✗
The ARP table is corrupted.
Why it's wrong here
ARP resolves IP addresses to MAC addresses on the local subnet only; the default gateway 192.168.1.1 already resolves, so ARP cannot explain failed internet reachability. Corrupted ARP entries would break LAN communication too. The fault lies beyond the gateway, such as missing NAT or DNS.
- ✗
The default gateway is missing.
Why it's wrong here
The stem already shows a default gateway of 192.168.1.1 in 'ip route', so this contradicts the stated evidence; a missing default route would also break LAN-external routing, not just internet access. It is tempting because a bad gateway commonly causes this symptom, and would be correct if 'ip route' showed no default entry.
- ✗
DNS resolution is failing.
Why it's wrong here
Pinging 8.8.8.8 by raw IP address bypasses name resolution entirely, so DNS failure cannot explain that result; it would instead break pings to hostnames. It is tempting because DNS misconfiguration is a frequent cause of 'no internet' reports, and would be correct if the ping to 8.8.8.8 succeeded but hostname lookups failed.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.