LPIC-2 Advanced Networking Configuration Practice Question
Which THREE conditions must be met for a Linux system to act as a router between two networks?
⚠ Common exam trap
Watch out — candidates often confuse the requirement for a default gateway (option B) with the need for specific routes to the networks being forwarded, but a router only needs routes to the destination networks, not a default gateway, unless it must forward traffic to networks beyond its directly connected ones.
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
✓
IP forwarding must be enabled in the kernel (net.ipv4.ip_forward = 1).
The Linux kernel must have IP forwarding enabled to forward packets between network interfaces. This is controlled by the sysctl parameter net.ipv4.ip_forward = 1, which allows the kernel to act as a router by forwarding IP packets from one interface to another based on the routing table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
IP forwarding must be enabled in the kernel (net.ipv4.ip_forward = 1).
Why this is correct
Required to forward packets.
- ✗
The system must have a default gateway configured.
Why it's wrong here
Not required; routing can be done without a default gateway.
- ✓
The system must have routes to the networks it will forward traffic to.
Why this is correct
Routes are needed to know where to send packets.
- ✓
Each interface must have an IP address in the respective subnet.
Why this is correct
Needed for the router to be on each network.
- ✗
The firewall must allow forwarding (FORWARD chain policy ACCEPT).
Why it's wrong here
Not a condition; forwarding can be allowed with rules, but it's not a condition for routing at the kernel level.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-2 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-2 exam.