LPIC-2 DNS, Web and Mail Services Practice Question
A system administrator notices that clients on the internal network can resolve the company's web server's hostname (www.example.com) using the internal DNS server (192.168.1.10), but external clients are unable to resolve it. The company uses BIND9 on an Ubuntu server. Which of the following configuration changes should be made on the DNS server to allow external resolution?
⚠ Common exam trap
Many candidates confuse 'listen-on' with 'allow-query' or recursion settings, mistakenly thinking that enabling recursion or opening query permissions is sufficient, when the server must first be reachable on the external IP address to accept any queries at all.
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
✓
Add a 'listen-on' statement for the external IP address.
The BIND9 DNS server is likely only listening on the internal IP address (192.168.1.10) by default, so external queries never reach the server. Adding a 'listen-on' statement for the external IP address (e.g., the public IP assigned to the server's external interface) allows BIND to accept and respond to DNS queries from external clients on that address, enabling external resolution of www.example.com.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add a 'listen-on' statement for the external IP address.
Why this is correct
The server must listen on the external interface to receive queries from outside.
- ✗
Enable recursion by setting 'recursion yes'.
Why it's wrong here
Recursion is for non-authoritative queries; the server is authoritative for the domain.
- ✗
Set the 'allow-query' option to 'any' in the options block.
Why it's wrong here
allow-query controls who can query; internal clients already succeed, so this is not the issue.
- ✗
Add an A record for www.example.com in the reverse zone.
Why it's wrong here
Reverse zone maps IP to hostname, not needed for forward resolution.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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