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LFCS Networking Practice Question

A system administrator is troubleshooting network connectivity from a server that can reach internal resources but cannot access the internet. The server's /etc/sysconfig/network-scripts/ifcfg-eth0 file contains: BOOTPROTO=static, IPADDR=10.0.0.10, NETMASK=255.255.255.0, GATEWAY=10.0.0.1. The administrator runs 'ip route show' and sees: default via 10.0.0.1 dev eth0. However, 'ping 8.8.8.8' fails. Which is the most likely cause?

⚠ Common exam trap

Candidates often assume a missing default gateway is the problem when ping fails, but the question explicitly shows the default route exists, so the real issue is the gateway's inability to forward traffic beyond the local network.

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 10.0.0.1 is not configured to forward traffic to the internet (no NAT or upstream route).

The routing table shows a default gateway (10.0.0.1) is present, so the issue is not a missing route. Since the server can reach internal resources but not the internet, the most likely cause is that the gateway itself (10.0.0.1) is not configured to perform NAT or does not have an upstream route to forward traffic beyond the local subnet. Without this, packets destined for 8.8.8.8 are sent to the gateway but are then dropped because the gateway has no path to the internet.

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 missing from the routing table.

    Why it's wrong here

    The default route is present, as shown.

  • The gateway 10.0.0.1 is not configured to forward traffic to the internet (no NAT or upstream route).

    Why this is correct

    The private IP gateway cannot route to the internet without NAT or a public IP.

  • DNS resolution is not configured.

    Why it's wrong here

    DNS is not required for pinging an IP address directly.

  • A firewall is blocking outbound ICMP traffic.

    Why it's wrong here

    There is no evidence of a firewall; the issue is more fundamental.

Visual reference

Inside (Private) PC-A 10.0.0.1 PC-B 10.0.0.2 NAT Router Outside (Public) 203.0.113.1 Inside Global Server PAT: many private IPs share one public IP via unique port numbers

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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.