DockerNetworking

Default Networks & Docker Network ls — DCA Practice Question

A representative Docker Certified Associate (DCA) exam question on Default Networks & Docker Network ls. Work through it below, then read why each option is right or wrong.

This question is part of the free Docker Certified Associate practice test.

Short answer

The correct answer is A. bridge, host, and none, where the none network uses the null driver.

The Question

A Linux host runs a freshly installed Docker Engine and nobody has created a network yet. Which networks does docker network ls list?

Abridge, host, and none, where the none network uses the null driverCorrect

Bbridge, overlay, and none, where overlay is the built-in multi-host network

Cbridge, host, and null, where null is the isolated network name

Dbridge, macvlan, and none, where macvlan is the LAN-facing network

Why A is correct

Why the other options are wrong

Option B: bridge, overlay, and none, where overlay is the built-in multi-host network

Option B does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (A) is the only one that fully meets every constraint stated in the question.

Option C: bridge, host, and null, where null is the isolated network name

Option C does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (A) is the only one that fully meets every constraint stated in the question.

Option D: bridge, macvlan, and none, where macvlan is the LAN-facing network

Option D does not satisfy the requirement in the scenario. Review the explanation above: the correct choice (A) is the only one that fully meets every constraint stated in the question.

Key idea: Default Networks & Docker Network ls

A is correct: a fresh Engine lists the predefined networks bridge, host, and none, and the DRIVER column shows null for none. B is wrong because overlay networks connect multiple daemons and need the hosts to be part of a swarm. C is wrong because null is the driver name of the none network, not a network name. D is wrong because a macvlan network exists only after someone creates it with docker network create -d macvlan. On the DCA exam, questions in the "Networking" domain test whether you can map a scenario's constraints to the right choice. Read the requirement carefully, eliminate options that violate any single constraint, and pick the one that satisfies all of them with the least operational overhead.

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Official sources used

Verify program and exam details at the source before scheduling.

docs.docker.comNetwork: ls docs.docker.comTutorials: Standalone