Kubernetes / Services, DNS & Traffic Routing
Diagnose a Service port pointing to the wrong container listener
A Service's client-facing port can differ from the backend port. A mismatch can make healthy Pods unreachable through the Service.
Environment and inputs: Kubernetes · kubectl with supported client/server versions and delegated RBAC. Examples use namespace app unless noted. Check context, namespace, APIs and provider support first.
Start with this check
Confirm the environment and replace sample objects, namespaces, images, paths and hosts with approved targets. Share only relevant, sanitized output. Follow the workload owner’s process for changes.
kubectl -n app get service web -o jsonpath='{.spec.ports}'Read the result
The port entries show port, targetPort and protocol. Named target ports must resolve against the selected Pods' declared port names.
Resolve and verify
Compare the mapping with the actual process listener and EndpointSlice ports. Correct the managed Service or workload definition and retest from an approved client.
Before changing production
Do not assume containerPort opens a listener or a TCP mapping validates a UDP workload.