DCA Communication & Stakeholder Relations 3 — Questions and Answers
Question 1: A network engineer needs to understand how Docker assigns DNS names to services in a user-defined bridge network. What is the default behavior?
- Containers are reachable by their name as DNS hostnames (Correct answer)
- Docker uses /etc/hosts only, no embedded DNS
- All containers share a single IP with different ports
- DNS resolution requires an external nameserver
Correct answer: Containers are reachable by their name as DNS hostnames
User-defined bridge networks include an embedded DNS server that resolves container names to their IP addresses automatically.
Question 2: A stakeholder wants to limit which containers can communicate on a shared host. Which Docker feature best enforces network segmentation?
- User-defined networks per team/application (Correct answer)
- Disabling inter-container communication globally
- Using only host networking
- Removing all container ports
Correct answer: User-defined networks per team/application
User-defined networks isolate container communication so only containers on the same network can communicate by default.
Question 3: During a post-incident review, a stakeholder asks which Docker component routes traffic between services in a Swarm. What is the correct answer?
- The ingress overlay network and routing mesh (Correct answer)
- A dedicated load balancer container
- Host firewall rules only
- Docker Compose networking
Correct answer: The ingress overlay network and routing mesh
Docker Swarm uses an ingress overlay network and routing mesh to distribute incoming traffic across service replicas.
Question 4: An SRE team wants to communicate resource constraints to developers. Which Docker flag limits a container's CPU usage?
- --cpus (Correct answer)
- --cpu-limit
- --max-cpu
- --cpu-cap
Correct answer: --cpus
The `--cpus` flag specifies the number of CPUs available to the container as a decimal value.
Question 5: A compliance officer asks how to audit which images are running in production Docker environments. What is the best approach?
- Use `docker ps --no-trunc` to list containers with full image digests (Correct answer)
- Read /var/lib/docker directly
- Check the Dockerfile only
- Review environment variables
Correct answer: Use `docker ps --no-trunc` to list containers with full image digests
`docker ps --no-trunc` shows full image IDs and names for all running containers, enabling audit of active images.
Question 6: A DevOps lead needs to share networking configuration with a new team member. Which file format does Docker Compose use to define networks?
- YAML (Correct answer)
- JSON
- TOML
- INI
Correct answer: YAML
Docker Compose uses YAML files (docker-compose.yml) to define services, networks, and volumes.
Question 7: A stakeholder requests that external clients communicate with a containerized web service on port 443. Which Docker flag publishes this port correctly?
- -p 443:443 (Correct answer)
- --expose 443
- --port-map 443
- -e PORT=443
Correct answer: -p 443:443
The `-p host_port:container_port` flag publishes a container port to the host, making it accessible externally.
DCA Communication & Stakeholder Relations 3
A network engineer needs to understand how Docker assigns DNS names to services in a user-defined bridge network.
What is the default behavior?