LPIC-2 Advanced Networking Configuration Practice Question
A Linux server is configured as a DNS resolver with BIND. Users report that they cannot resolve external hostnames. The server can resolve internal names. Which of the following is the most likely cause?
⚠ Common exam trap
It's easy for candidates to assume missing forwarders (Option B) is the cause, but BIND can resolve externally via root hints without forwarders, so the real issue is a firewall blocking outbound UDP 53, which selectively breaks external resolution while internal resolution remains intact.
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 firewall is blocking UDP port 53 outgoing from the server.
The server can resolve internal names, indicating that the local BIND service is functioning correctly for authoritative zones. However, external resolution fails, which typically means the server cannot reach upstream DNS servers. Outgoing UDP port 53 is required for DNS queries to external resolvers; if the firewall blocks this traffic, the server cannot forward queries to the internet, while internal queries (often served from local zones) remain unaffected.
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 server's /etc/resolv.conf points to itself.
Why it's wrong here
That is typical and not a problem as long as BIND listens on localhost.
- ✗
The forwarders directive is missing from named.conf.
Why it's wrong here
Without forwarders, BIND can still resolve using root hints, though slowly; it would not completely fail.
- ✓
The firewall is blocking UDP port 53 outgoing from the server.
Why this is correct
If outgoing DNS queries are blocked, external resolution fails, but internal zones can still be answered from local authoritative data.
- ✗
The named daemon is not running.
Why it's wrong here
If named were not running, internal resolution would also fail.
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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.