130 lines
3.5 KiB
Markdown
130 lines
3.5 KiB
Markdown
# Docker Networks
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## Current Landscape (May 16, 2026)
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Each Docker Compose stack creates its own `{stack}_default` bridge network when it
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has no explicit `networks:` declaration. This has exhausted Docker's built-in
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172.x.x.x/16 address pool, triggering CIDR overlap errors.
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### Networks & Subnets
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| Network | Subnet | Containers |
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|---|---|---|
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| `bridge` (built-in) | 10.0.0.0/24 | 0 |
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| `ai-internal` | 172.31.0.0/16 | 8 |
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| `arcane_default` | 172.22.0.0/16 | 1 |
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| `arr-stack_default` | 172.21.0.0/16 | 4 |
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| `daytona-minimal_daytona-network` | 172.23.0.0/16 | 4 |
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| `dozzle_default` | 192.168.16.0/20 | 1 |
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| `homepage_default` | 172.19.0.0/16 | 1 |
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| `immich_default` | 172.18.0.0/16 | 5 |
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| `karakeep_default` | 172.30.0.0/16 | 3 |
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| `memos_default` | 192.168.32.0/20 | 1 |
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| `n8n_default` | 172.25.0.0/16 | 1 |
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| `ntfy_default` | 172.27.0.0/16 | 1 |
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| `nuc-ai-core_default` | 172.29.0.0/16 | 1 |
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| `paperless-ngx_default` | 172.28.0.0/16 | 5 |
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| `pocketid_default` | 172.20.0.0/16 | 1 |
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| `qdrant_default` | 172.24.0.0/16 | 1 |
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| `traccar_default` | 172.26.0.0/16 | 1 |
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| `vaultwarden_default` | 192.168.64.0/20 | 1 |
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| `vpn_default` | 192.168.80.0/20 | 1 |
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Total: 19 user-defined bridge networks.
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### Problem
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Docker's default address pool for user-defined bridge networks is
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172.17.0.0/16 – 172.31.0.0/16 (15 subnets max). With 15 172.x.x.x/16 networks
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already allocated, there is no room for new ones.
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The Daytona runner (`daytona-minimal-runner-1`) programmatically creates a
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`runner-bridge` network on startup. It fails with:
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```
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Error response from daemon: invalid pool request: Pool overlaps with other one
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on this address space
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```
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## Consolidation Plan
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### shared_backend Network
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A single shared bridge network (`shared_backend`) has been created to replace
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per-stack defaults for lightweight services that don't need isolation.
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### Stacks Already Migrated
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- arcane
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- dozzle
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- ntfy
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- qdrant
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- traccar
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- vaultwarden
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- memos
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- n8n
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- pocketid
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These stacks now declare:
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```yaml
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networks:
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default:
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external: true
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name: shared_backend
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```
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### How to Free Subnets
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After migrating a stack to `shared_backend`, recreate it and prune the old network:
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```bash
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cd /opt/stacks/{stack} && docker compose up -d
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docker network rm {stack}_default # after containers disconnect
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```
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### Stacks Keeping Own Networks
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These stacks have complex internal networking and should keep their own:
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- **immich** — 5 services with inter-dependencies
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- **paperless-ngx** — 5 services (webserver, broker, db, gotenberg, tika)
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- **arr-stack** — 5 services (rdtclient, prowlarr, audiobookshelf, shelfarr, flaresolverr)
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- **daytona** — explicit `daytona-minimal_daytona-network`
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- **karakeep** — 3 services with chrome dependency
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- **homepage** — single service, can stay or migrate
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- **streamio** — already removed, stremio uses VPN container directly
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- **vpn** — single service, can stay or migrate
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- **ai/*_ai** — AI stacks, untouched
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### Long-term Fix
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Add `default-address-pools` to `/etc/docker/daemon.json`:
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```json
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{
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"default-address-pools": [
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{"base": "10.0.0.0/8", "size": 24}
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]
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}
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```
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This gives 65536 /24 subnets, eliminating exhaustion. Requires Docker daemon
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restart (`systemctl restart docker`), which briefly disrupts all containers.
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## Commands
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```bash
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# List all networks
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docker network ls
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# Inspect a network
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docker network inspect {name}
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# Remove unused networks
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docker network prune
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# Remove a specific network (must have 0 containers)
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docker network rm {name}
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```
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