LPIC-2 DNS, Web and Mail Services Practice Question
An administrator needs to configure a BIND DNS server to allow dynamic updates from a specific subnet (192.168.1.0/24) for the zone 'example.com'. The administrator must also ensure that the zone file is updated immediately after a dynamic update. Which configuration accomplishes this?
⚠ Common exam trap
Many candidates confuse `allow-update` with `allow-transfer` or `also-notify`, mistakenly thinking those directives enable dynamic updates, or they misapply `update-policy` syntax by using a subnet instead of a key-based identity.
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
✓
zone "example.com" { type master; file "db.example.com"; allow-update { 192.168.1.0/24; }; };
The `allow-update` statement in BIND explicitly permits dynamic DNS updates (RFC 2136) from specified sources, such as the subnet 192.168.1.0/24. Dynamic updates are written to the zone file immediately by default when using a master zone, ensuring the file is updated in real time.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
zone "example.com" { type master; file "db.example.com"; update-policy { grant 192.168.1.0/24 zonesub ANY; }; };
Why it's wrong here
update-policy is used for fine-grained access control typically with TSIG keys, not for IP-based grants.
- ✗
zone "example.com" { type master; file "db.example.com"; allow-transfer { 192.168.1.0/24; }; };
Why it's wrong here
allow-transfer controls zone transfers, not dynamic updates.
- ✓
zone "example.com" { type master; file "db.example.com"; allow-update { 192.168.1.0/24; }; };
Why this is correct
allow-update permits dynamic updates from the subnet. The zone file is updated immediately on each update.
- ✗
zone "example.com" { type master; file "db.example.com"; also-notify { 192.168.1.0/24; }; };
Why it's wrong here
also-notify specifies additional servers to notify, unrelated to dynamic updates.
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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.