LPIC-1 Essential System Services and Networking Practice Question
After running 'ip route show default', a system administrator sees no output. Users on that system can only communicate with hosts on the local subnet. What is the most likely cause?
⚠ Common exam trap
Candidates often confuse DNS resolution with routing, assuming that name resolution failure is the root cause, when in fact the absence of a default gateway directly prevents any off-subnet IP communication regardless of DNS status.
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 missing
The `ip route show default` command displays the default gateway entry in the routing table. An empty output indicates that no default route is configured. Without a default gateway, the system cannot route packets to destinations outside its local subnet, which explains why users can only communicate with hosts on the local subnet.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DNS is misconfigured
Why it's wrong here
DNS issues would not prevent IP communication to non-local hosts if route exists.
- ✗
A firewall is blocking all traffic
Why it's wrong here
A firewall blocking traffic would not remove the default route from the routing table, and local subnet traffic still flows. The empty default route output shows no gateway is configured. Firewall rules would be the cause when routes exist but specific ports or protocols are silently dropped.
- ✗
The network interface is down
Why it's wrong here
A down interface cannot carry local subnet traffic at all, so users could not reach same-subnet hosts either. The absence of a default route alongside working local connectivity points to a missing gateway configuration. Interface state would be the cause when no connectivity exists whatsoever, including to local peers.
- ✓
The default gateway is missing
Why this is correct
With no default route in the routing table, the kernel has no next-hop for off-subnet destinations, so packets are dropped and only local-subnet hosts remain reachable. Adding a default gateway restores forwarding beyond the local subnet.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.