Technical interview guide

DNS & DHCP

How devices get an IP address automatically, and how domain names get resolved into one.

Read: 45 min
Practice MCQs: 25
Interview QA: 25
Edition: v4
Editorial status: Reviewed
Relevant for: Network Engineer

Scope: Current IETF DNS, negative caching, DNSSEC, DNS over TCP/TLS/HTTPS, DHCPv4/options/relay, DHCPv6, SLAAC, and mDNS references reviewed 2026-09-04.

Interview QA

Treat each question like a live interview question: answer out loud first (structure, assumptions, tradeoffs), then open the model answer to spot gaps and rehearse a tighter follow-up.

Curated: 2026-10-05 · Written: 2026-09-09 · Reviewed: 2026-10-03

QA-1

Trace a DNS lookup from application to authority.

QA-2

Diagnose a lame DNS delegation.

QA-3

Review a DNS delegation and glue change.

QA-4

Plan a low-risk DNS endpoint migration.

QA-5

Diagnose a newly created record that some users still cannot resolve.

QA-6

Design an alias for a service name safely.

QA-7

Plan a safe DNSSEC signing and rollover.

QA-8

Choose and govern encrypted DNS for managed clients.

QA-9

Diagnose DNS that works for small answers but fails for DNSSEC or large records.

QA-10

Design split DNS for remote and office clients.

QA-11

Use mDNS without conflicting with enterprise DNS.

QA-12

Trace DHCPv4 address acquisition across a relay.

QA-13

Design resilient DHCP relay service.

QA-14

Design and test DHCP lease lifecycle and failover.

QA-15

Use reservations safely for infrastructure devices.

QA-16

Review DHCP scope and option configuration.

QA-17

Capacity-plan and respond to DHCP pool exhaustion.

QA-18

Detect and contain rogue DHCP.

QA-19

Design IPv6 SLAAC and DHCPv6 configuration.

QA-20

Diagnose intermittent IPv6 duplicate-address failures.

QA-21

Integrate DHCP leases with dynamic DNS securely.

QA-22

Design DNS observability and SLOs.

QA-23

Design DHCP observability and alerting.

QA-24

Recover DHCP after database corruption or split brain.

QA-25