🚨 Docker Error Guide: 'network <name> not found' — Missing or Stale Docker Network

Overview

Docker attaches containers to named networks by ID. When you reference a network that no longer exists — because it was pruned, never created, or recreated with a new ID — the daemon cannot resolve the name and returns:

Error response from daemon: network myapp_backend not found

You will also see the ID-based form when a container’s stored network reference is stale:

Error response from daemon: network 7f3c9a2b1d4e not found

Symptoms

• docker run --network myapp_backend ... fails immediately before the container starts.
• docker compose up complains that an external: true network does not exist.
• docker start <container> fails after a docker network prune removed the network it was attached to.
• docker network connect <net> <container> reports the target network is missing.

Common Root Causes

• The network was pruned — docker network prune or docker system prune removed an unused network that a stopped container still referenced.
• A Compose project was torn down — docker compose down removed the project’s default network, but you tried to reuse a container or run a one-off docker run against it.
• external: true without creating it — Compose expects a pre-existing network you never ran docker network create for.
• A recreated network has a new ID — deleting and re-creating a network gives it a fresh ID; containers pinned to the old ID break.
• Typo or wrong project prefix — Compose prefixes networks with the project name (myapp_backend), and the name you typed does not match.

Diagnostic Workflow

List what networks actually exist and their IDs:

docker network ls

Inspect the exact name Compose expects versus what is present:

docker compose config | grep -A5 networks
docker network ls --filter name=myapp

See which network a broken container is pinned to:

docker inspect --format '{{json .NetworkSettings.Networks}}' <container>

If a network exists but looks orphaned, inspect its endpoints:

docker network inspect myapp_backend

Check daemon logs for network lifecycle events:

journalctl -u docker --since '30 min ago' | grep -i network

Example Root Cause Analysis

An engineer ran a nightly docker system prune -f cron job, then found the monitoring stack would not restart with network monitoring_default not found. docker network ls confirmed the network was gone. The prune had removed monitoring_default because at prune time all its containers were stopped, so Docker considered the network unused. The stopped containers still held a reference to the now-deleted network ID.

The fix was to recreate the stack’s networking cleanly rather than patch individual containers:

docker compose down --remove-orphans
docker compose up -d

docker compose up recreates the project network and reattaches every service, resolving all stale references at once. Going forward the cron job was changed to docker system prune -f scoped away from networks in active use by scheduling it only after the stack was confirmed up.

Prevention Best Practices

• Prefer docker compose down + docker compose up to recreate a whole project rather than reattaching individual containers to networks by ID.
• For external: true networks, create them once explicitly (docker network create shared_net) and treat them as managed infrastructure.
• Scope pruning: avoid blanket docker system prune on hosts running stopped-but-needed stacks, or exclude in-use networks.
• Reference networks by stable name, never by hard-coded ID, in scripts and automation.
• Keep Compose project names consistent (-p or COMPOSE_PROJECT_NAME) so network name prefixes stay predictable.

Quick Command Reference

docker network ls                                  # list existing networks
docker network inspect <name>                      # endpoints + config
docker network create myapp_backend                # (re)create an external net
docker compose up -d                               # recreate project networking
docker inspect --format '{{json .NetworkSettings.Networks}}' <ctr>
docker network prune                               # remove only unused networks

Conclusion

network <name> not found means Docker cannot resolve the network reference to an existing ID — usually because a prune removed it, a Compose teardown deleted it, or an external network was never created. Confirm what exists with docker network ls, then recreate the network or, better, recreate the whole Compose project so every container is reattached consistently. Scoping prunes and treating shared networks as managed resources prevents recurrence. See more in the Docker guides.