DNS — Name Resolution

What is it?

DNS resolves names into records such as IPv4 A or IPv6 AAAA answers.

Why should I learn it?

A DNS failure is often mistaken for a full network outage, so ruling it out early saves troubleshooting time.

How it works

Client queries its resolver → resolver returns a record → client connects using the returned IP.

Real-world example

The client asks its configured resolver, receives an answer, then starts the real connection to the returned IP. DNS resolution and application connectivity are separate steps.

Troubleshooting mindset

If IP reachability works but names fail, test DNS directly before changing routing.

Common mistake

Do not memorise the definition without connecting it to packet flow, device state and verification. Ask: what should happen, what actually happened, and which command or capture can prove the difference?

Quick recap

• Understand the job of the protocol or feature.
• Know where it sits in the traffic path.
• Verify behaviour instead of guessing.
• Connect the topic to the next networking layer.

Interview connection

Explain the concept in simple words first. Then give one practical example or troubleshooting check. That is stronger than repeating a textbook definition.

References & Further Reading

• How to Master CCNA — supplied reference material.
• CCNA Notes — supplied technical/configuration reference.