305-300 Container Virtualization Practice Question
You are troubleshooting a Docker container that cannot reach the internet despite the host having connectivity. The container uses the default bridge network. Which iptables chain is most likely causing the block?
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
✓
FORWARD
Docker adds rules to the FORWARD chain in the filter table to manage traffic between the bridge network and external networks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
PREROUTING
Why it's wrong here
This belongs to the nat table and handles destination NAT.
- ✗
POSTROUTING
Why it's wrong here
This is used for masquerading (SNAT) traffic leaving the host.
- ✓
FORWARD
Why this is correct
Docker injects rules into the FORWARD chain to control inter-network traffic.
- ✗
OUTPUT
Why it's wrong here
The OUTPUT chain handles packets originating from the host, not container traffic.
About these practice questions
Courseiva writes every 305-300 question from scratch — 194 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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official LPI exam blueprint
This 305-300 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 305-300 exam.