Docker / Networking, Ports & Service Connectivity
Distinguish a Swarm overlay network from a local bridge
An overlay depends on multi-host prerequisites and network membership. Creating a similarly named local network does not establish the same connectivity.
Environment and inputs: Docker Engine · Compose v2 and Buildx where specified; Linux containers unless noted. Verify daemon context, installed feature support and authorized host or Swarm manager access 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.
docker network inspect --format '{{.Scope}} {{.Driver}} {{.Attachable}}' appnetRead the result
Scope, driver and attachability describe network intent. Manager access, node connectivity and endpoint membership are separate checks.
Resolve and verify
Compare the actual Swarm topology, supported ports and application attachments with the incident. Repair the demonstrated node or overlay dependency through the platform owner.
Before changing production
Do not create parallel networks or expose cluster-management ports broadly to make cross-host traffic work.