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200-901 Practice Question: Is troubleshooting a Kubernetes deployment where…
A network engineer is troubleshooting a Kubernetes deployment where pods are failing to start with the error 'CrashLoopBackOff'. The pod log shows 'bind: address already in use'. The deployment runs multiple replicas of a container that listens on port 8080. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between hostPort (which binds to the node's IP) and containerPort (which is informational), leading candidates to overlook that hostPort causes direct port conflicts on the same node.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The deployment has hostPort: 8080 specified, causing port conflict when multiple replicas are scheduled on the same node.
The 'bind: address already in use' error indicates that the container's process cannot bind to port 8080 because it is already occupied. When `hostPort: 8080` is specified in the pod spec, Kubernetes instructs the container runtime to map the container port to the same port on the node's network namespace. If multiple replicas of the deployment are scheduled on the same node, each pod attempts to bind to port 8080 on the host, causing a conflict and the CrashLoopBackOff state. This is a common misconfiguration when using hostPort without ensuring that replicas are spread across different nodes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The container is attempting to bind to a privileged port without the necessary capabilities.
Why it's wrong here
Port 8080 is not privileged (privileged ports are below 1024).
- ✓
The deployment has hostPort: 8080 specified, causing port conflict when multiple replicas are scheduled on the same node.
Why this is correct
hostPort reserves the port on the host node, so only one pod per node can use it. With multiple replicas, subsequent pods fail with address in use.
- ✗
The service is using NodePort and the node port is already in use.
Why it's wrong here
NodePort is a service type; the error occurs at the container level, not the service level.
- ✗
Multiple containers in the same pod are trying to bind to the same port.
Why it's wrong here
Containers in a pod share the same network namespace; they cannot bind to the same port, but the error would occur at pod creation, not as CrashLoopBackOff after start.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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