hardMultiple ChoiceObjective-mapped
XK0-006 Practice Question: A Linux administrator is troubleshooting network…
A Linux administrator is troubleshooting network connectivity. The server can ping its own IP address but cannot ping the default gateway. The output of 'ip route show' is: 'default via 10.0.0.1 dev eth0 proto static metric 100'. The output of 'ping -c 1 10.0.0.1' fails with 'Destination Host Unreachable'. Which of the following is the MOST likely cause?
⚠ Common exam trap
It's easy for candidates to assume 'Destination Host Unreachable' always means the gateway is down, but in Linux this error specifically indicates the local host cannot find a layer-2 path to the destination, typically due to a subnet mask mismatch or missing ARP entry.
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 subnet mask on eth0 is incorrect, causing the gateway to be considered on a different network.
The server can ping its own IP address, confirming that the local network stack and the eth0 interface are operational. However, the 'Destination Host Unreachable' error when pinging the default gateway (10.0.0.1) indicates that the host does not have a valid route to that destination. Since the default route exists, the most likely cause is an incorrect subnet mask on eth0, which causes the kernel to treat the gateway as being on a different network, thus failing to send ARP requests or forward packets to it.
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 eth0 interface is down.
Why it's wrong here
If eth0 were down, the own IP ping would also fail.
- ✗
The gateway is down or not responding.
Why it's wrong here
A down gateway would typically cause timeouts, not 'unreachable' from the local host.
- ✗
The default gateway is not set.
Why it's wrong here
The route table shows a default gateway is set.
- ✓
The subnet mask on eth0 is incorrect, causing the gateway to be considered on a different network.
Why this is correct
A wrong subnet mask can make the gateway appear on a different subnet, leading to 'unreachable'.
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Linux Fundamentals and History
Key term
Linux
Linux is an open-source operating system that manages computer hardware and software, widely used in servers, desktops, and embedded systems.
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This XK0-006 practice question is part of Courseiva's free CompTIA 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 XK0-006 exam.