Add docker/networks/README.md

docker/networks/README.md

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+# Docker Networks
+
+## Purpose
+
+Docker networks allow containers to communicate with each other while remaining isolated from other containers and the host system.
+
+## Networks in Use
+
+| Network                  | Purpose                  |
+| ------------------------ | ------------------------ |
+| bridge                   | Default Docker network   |
+| compose-practice_default | Docker Compose nginx lab |
+| gitea_default            | Gitea service            |
+| npm_default              | Nginx Proxy Manager      |
+| portainer_default        | Portainer                |
+| uptime-kuma_default      | Uptime Kuma              |
+
+## Observations
+
+Each Docker Compose stack automatically creates its own network.
+
+Examples:
+
+| Service                  | Container IP |
+| ------------------------ | ------------ |
+| uptime-kuma              | 172.17.0.2   |
+| compose-practice-nginx-1 | 172.18.0.2   |
+| gitea                    | 172.19.0.2   |
+| npm                      | 172.20.0.2   |
+| portainer                | 172.21.0.2   |
+
+## Commands
+
+View networks:
+
+```bash
+docker network ls
+```
+
+Inspect a network:
+
+```bash
+docker network inspect NETWORK_NAME
+```
+
+Example:
+
+```bash
+docker network inspect gitea_default
+```
+
+## Lessons Learned
+
+* Every Compose stack gets its own network.
+* Containers communicate using private Docker IP addresses.
+* Containers on separate networks cannot automatically communicate with each other.
+* Docker networks provide isolation and security.
+* Reverse proxies often require containers to share a network.
+
+## Date Created
+
+June 15, 2026