# Incident: Traefik IP Collision on dockerproxy Network

**Date:** 2026-05-17 (root cause 04:02–04:39 UTC)
**Severity:** P1 — full reverse-proxy outage
**Status:** Resolved
**Affected:** all `*.xtrm-lab.org` services routed through Traefik (vaultwarden, authentik, gitea, uptime-kuma, transmission, urbackup, unimus, netalert, openbrain, ~70 others)

---

## Symptoms

- `traefik` container stuck in `Created` state, never reached `Running`.
- `docker inspect traefik` reported:
  - `State.Status: created`
  - `State.Error: failed to set up container networking: Address already in use`
  - `State.ExitCode: 128`
- All `*.xtrm-lab.org` hostnames unreachable through the proxy.
- `traefik-manager` sidecar remained healthy but isolated.

---

## Root Cause

Static-IP collision on the `dockerproxy` Docker bridge (`172.18.0.0/16`).

Timeline (UTC):
- **04:02:40** — `ewa-apps` (Dockge stack at `/mnt/user/appdata/dockge/stacks/ewa-apps`) restarted. Its compose joined `dockerproxy` without `ipv4_address`, so Docker handed it the lowest free IP: **172.18.0.3** (Traefik's reserved IP, but Traefik was momentarily down).
- **04:39:09** — `traefik` was recreated and requested its IPAMConfig-reserved `172.18.0.3`. Already taken — container left in `Created`.

`dockerproxy` is a user-defined bridge where critical services have hard-coded static IPs (traefik=.3, postgresql17=.10, vaultwarden=.15, etc.) but several stacks (`ewa-apps`) had no reservation. First-to-start wins the IP race.

---

## Resolution

1. `docker stop ewa-apps` (released .3)
2. `docker start traefik` (claimed .3 via IPAMConfig)
3. `docker start ewa-apps` (got .4)
4. Logs immediately showed Authentik/Traefik routing chains resuming.

---

## Preventive Fix

Pinned static IP for `ewa-apps` in its Dockge compose:

```yaml
networks:
  dockerproxy:
    ipv4_address: 172.18.0.70
```

Backup of original at `/mnt/user/appdata/dockge/stacks/ewa-apps/compose.yaml.bak.2026-05-17`.

Final state after `docker compose up -d`:

| Container | IP |
|-----------|-----|
| traefik | 172.18.0.3 |
| ewa-apps | 172.18.0.70 |

---

## Follow-up

- Audit remaining Dockge stacks on `dockerproxy` for missing `ipv4_address` reservations.
- Add a Uptime Kuma docker-state monitor for `traefik` (HTTP probes route *through* Traefik and fail uselessly when Traefik itself is the outage).
- Two Traefik-IP incidents in 12 days (also 2026-05-05 vaultwarden misroute) — consider a deliberate redesign of the dockerproxy IP map.