LFCS Networking Practice Question
Exhibit
Refer to the exhibit.
# ip addr show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:1a:2b:3c:4d:5e brd ff:ff:ff:ff:ff:ff
inet 192.168.10.15/24 brd 192.168.10.255 scope global dynamic eth0
valid_lft 86399sec preferred_lft 86399sec
inet6 fe80::21a:2bff:fe3c:4d5e/64 scope link
valid_lft forever preferred_lft forever
# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.10.1 0.0.0.0 UG 0 0 0 eth0
192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
# ping -c 1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
From 192.168.10.15 icmp_seq=1 Destination Host UnreachableBased on the exhibit, a system administrator runs ping to 8.8.8.8 and gets 'Destination Host Unreachable'. What is the most likely cause?
⚠ Common exam trap
A common mix-up: candidates confuse 'Destination Host Unreachable' (which indicates a local routing or next-hop reachability issue) with 'Request Timed Out' (which typically indicates a remote firewall or network congestion), leading them to incorrectly select a firewall blocking ICMP.
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 gateway 192.168.10.1 is not reachable from this host.
The 'Destination Host Unreachable' message indicates that the host has no route to the destination network or the next-hop gateway is not reachable. Since the ping target is 8.8.8.8 (a public IP), the host must forward traffic to its default gateway. If the gateway 192.168.10.1 is not reachable (e.g., due to a down interface, ARP failure, or missing neighbor entry), the kernel will immediately return this ICMP error without attempting to send the packet.
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 IP address 192.168.10.15 is not configured on eth0.
Why it's wrong here
The IP is configured as shown in ip addr.
- ✗
A firewall is blocking ICMP traffic.
Why it's wrong here
The error is 'Destination Host Unreachable', not 'Request timed out', suggesting a routing issue rather than a firewall block.
- ✓
The gateway 192.168.10.1 is not reachable from this host.
Why this is correct
The ping error indicates the gateway cannot be reached, likely because it's down or not on the same network.
- ✗
The default route is missing.
Why it's wrong here
The default route is present (0.0.0.0 via 192.168.10.1).
Go deeper
Related to this question
About these practice questions
Courseiva writes every LFCS question from scratch — 507 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
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.