LFCS Networking Practice Question
Network Topology
Based on the iptables-save output, what is the default policy for the FORWARD chain and what happens to a new SSH connection from an external host on eth0?
⚠ Common exam trap
It's easy for candidates to confuse the default policy with the actual behavior for specific traffic, assuming that a DROP default policy means all traffic is dropped, ignoring the effect of explicit ACCEPT rules.
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
✓
Default policy FORWARD is DROP; SSH connections are accepted.
The default policy for the FORWARD chain is DROP, as shown in the iptables-save output (e.g., `:FORWARD DROP [0:0]`). A new SSH connection from an external host on eth0 is accepted because there is a rule in the FORWARD chain that matches incoming SSH traffic (typically TCP port 22) and has a target of ACCEPT, overriding the default DROP policy for that specific traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Default policy FORWARD is ACCEPT; SSH connections are dropped.
Why it's wrong here
FORWARD default is DROP, and SSH is accepted.
- ✗
Default policy FORWARD is DROP; SSH connections are dropped.
Why it's wrong here
SSH is accepted by the explicit rule.
- ✓
Default policy FORWARD is DROP; SSH connections are accepted.
Why this is correct
FORWARD default is DROP; SSH rule allows traffic on port 22.
- ✗
Default policy FORWARD is ACCEPT; SSH connections are accepted.
Why it's wrong here
FORWARD default is DROP.
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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.