The Docker Container Is Running, the Port Is Dead: A Complete Walkthrough of a Silent Host-Bind Failure

Sat, 13 Jun 2026 07:30:00 +0800

TL;DR:

docker ps says everything is fine. docker inspect’s HostConfig.PortBindings clearly says 203.0.113.14:3001:3000. But on the host, no docker-proxy is listening, the iptables nat/DOCKER chain has no DNAT rule, and NetworkSettings.Networks and Ports are both empty {}. This “container alive, port dead” state is what happens when libnetwork silently rolls back the endpoint creation because the target interface wasn’t up at attach time — and Docker doesn’t bother to tell you that the port publish never actually happened. The fix is a single 30-second command: docker network connect <net> <ctr>.

Postmortem on Margrop Blog

The Docker Container Is Running, the Port Is Dead: A Complete Walkthrough of a Silent Host-Bind Failure