LFCS Networking Practice Question
A Linux server has two network interfaces: eth0 (192.168.1.10/24) and eth1 (10.0.0.10/24). The administrator wants to configure the server to route traffic between the two networks. Which two actions are required? (Choose two.)
⚠ Common exam trap
The trap here is assuming that NAT or static routes are needed for internal routing, when only forwarding and firewall permissions are required.
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
✓
Configure iptables FORWARD rules to accept traffic between the interfaces.
To route traffic between two directly connected networks, the server must have IP forwarding enabled and firewall rules that permit forwarding. Connected routes already exist, so static routes for those networks are not needed. NAT is not required for internal routing, and client gateway configuration is done on the clients, not the server.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the default gateway on both client networks to point to the server's respective interface addresses.
Why it's wrong here
While clients on each network need a route to reach the other network, they can use the server as their gateway. However, this action is performed on the clients, not on the server itself. The question asks for actions on the server to enable routing, so this is not one of the required server-side steps.
- ✗
Enable NAT (masquerading) on the server for both networks.
Why it's wrong here
NAT is used when private addresses need to access external networks, but here both networks are internal and can be routed directly. NAT would hide the original source addresses, which is unnecessary and can complicate troubleshooting. The requirement is simple routing, not address translation.
- ✓
Configure iptables FORWARD rules to accept traffic between the interfaces.
Why this is correct
By default, many distributions have a firewall that drops forwarded packets. Adding iptables FORWARD rules to accept traffic ensures that packets are not blocked by the firewall. This is required in addition to enabling IP forwarding for the server to route traffic successfully.
- ✗
Add static routes on the server for both networks.
Why it's wrong here
The server already has connected routes for both networks because its interfaces are configured with addresses in those subnets. Adding static routes for directly connected networks is unnecessary and can cause conflicts. Static routes are needed for remote networks not directly attached.
- ✓
Enable IP forwarding by setting net.ipv4.ip_forward=1.
Why this is correct
Enabling IP forwarding is essential for the kernel to forward packets between interfaces. Without it, the kernel drops packets not destined for itself. Setting net.ipv4.ip_forward=1 allows the server to act as a router, forwarding traffic between the 192.168.1.0/24 and 10.0.0.0/24 networks.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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.