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Unofficial practice

DNS and Route First Response

A host cannot reach a name or address. Separate routing, interface selection, and DNS resolution before blaming the application.

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Try first

ip route get 1.1.1.1 && dig +short example.com

Troubleshooting ladder

  1. Name the symptom.
  2. Inspect read-only state.
  3. Find the owner, service, file, device, mount, or route.
  4. Read the decisive output field.
  5. Choose the next narrow command.
  6. Avoid broad or destructive changes.
  7. Make the smallest justified change if required.
  8. Verify and record what changed.

drill evidence

Sample output and answer key

Command anatomy

ip route get 1.1.1.1 && dig +short example.com
ip route
show which route would be used
resolvectl/dig
test name resolution
ss
show listening sockets when relevant
destination
the host, name, or port being tested

Annotated output

1.1.1.1 via 192.168.10.1 dev wlan0 src 192.168.10.132 uid 1000
example.com: 93.184.216.34 -- link: wlan0
93.184.216.34

What to notice

via
the gateway used
dev
the interface selected
src
the local address chosen
resolved address
whether DNS returned an answer

Safe vs unsafe move

Common wrong move

Calling it a DNS outage when the route or gateway is wrong.

Next safe command

resolvectl status

Goal

Prove the condition with command output before changing the system.

Safe first command

ip route get 1.1.1.1 && dig +short example.com

Correct interpretation

The decisive fields are `via`, `dev`, `src`. The affected object is the selected route, interface, source address, or resolved name. The next safe command is `resolvectl status` because it narrows the evidence without jumping to a broad fix. Watch out for this wrong move: Calling it a DNS outage when the route or gateway is wrong.

Next safe command

resolvectl status

Common wrong move

Calling it a DNS outage when the route or gateway is wrong.

Self-check

Which field proves the selected gateway or interface, and which result proves DNS answered?

source and objective

Related cert objective

Source status: Linux Foundation LFCS page verified June 30, 2026. LFCS is an online, proctored, performance-based command-line exam.

Open related practice area

Related command pages

Why this matters

The point is not to memorize a flag. It is to read the evidence, name the next safe check, and avoid the tempting broad fix.