LPIC-2 DNS, Web and Mail Services Practice Question
You are the administrator of a medium-sized company that runs its own authoritative DNS servers for the domain 'company.com'. The primary DNS server is a BIND9 master, and there are two slaves. Recently, you updated the zone file on the master to add a new subdomain 'lab.company.com' with an A record pointing to 10.0.0.10. After the update, you increased the serial number and ran 'rndc reload'. However, after several hours, some external clients report that they cannot resolve 'lab.company.com'. You check the master server and find that the zone file contains the new record. You also check the slave servers and find that they still have the old zone data. The serial number on the master is 2025011501, while the slaves show 2025011400. The master's syslog shows no errors. The slaves' syslogs show 'zone company.com/IN: Transfer started.' but no completion messages. Firewall rules allow TCP and UDP port 53 between all DNS servers. What should you do to resolve the issue?
⚠ Common exam trap
Candidates often assume the serial number mismatch alone will eventually trigger a transfer via the slave's refresh timer, but the question emphasizes that hours have passed and the transfer started but never completed, indicating a stalled TCP connection that requires a forced NOTIFY to re-initiate the transfer.
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
✓
Run 'rndc notify company.com' on the master to force sending NOTIFY messages to the slaves.
The master's syslog shows no errors and the slaves' logs indicate a transfer started but never completed, which suggests the NOTIFY messages were sent but the slaves may have missed or ignored them due to a transient issue. Running 'rndc notify company.com' forces the master to re-send NOTIFY messages to all configured slaves, prompting them to initiate a zone transfer immediately, which should update the stale zone data on the slaves.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check the 'allow-transfer' ACL on the master; it might be restricting transfers to the slaves.
Why it's wrong here
The logs show 'Transfer started', so the master allowed the connection; the problem is the transfer not completing, possibly due to data transfer issues.
- ✗
Increase the serial number again on the master to a higher value and wait for the slaves to refresh.
Why it's wrong here
The slaves are not contacting the master, likely because they haven't received a NOTIFY. Increasing serial number alone won't trigger a transfer without a NOTIFY or refresh interval.
- ✗
Restart the BIND service on the slave servers.
Why it's wrong here
Restarting slaves might cause them to check the serial number at startup, but it is not guaranteed and may cause brief downtime.
- ✓
Run 'rndc notify company.com' on the master to force sending NOTIFY messages to the slaves.
Why this is correct
This will cause the master to send NOTIFY messages to all configured slaves, prompting them to start a zone transfer.
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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.