Today I went deep into Docker internals. Here are my notes on Network Isolation and Dockerfile instructions.
🔗 Docker Networking: The Big Three
I learned that network isolation is handled by namespaces. Depending on the driver, we can tighten or loosen this isolation.
Bridge (--network bridge)
Isolation: ✅ High.
Behavior: The default. Containers get private IPs. Traffic is NAT-ed through the host.
Use Case: Most standard web apps.
Host (--network host)
Isolation: ❌ None.
Behavior: The container hijacks the host's network stack. No port mapping needed.
Use Case: High-performance networking or when you need to handle thousands of ports.
None (--network none)
Isolation: 🔒 Maximum.
Behavior: No network card. Only loopback.
Use Case: Secure offline batch processing.
(Honorable mention to Overlay networks for multi-host setups, though that's a different beast than the single-host isolation drivers above.)
Why? ADD is unpredictable. If you try to copy a compressed backup file, ADD might silently extract it, corrupting your image state. COPY is explicit—what you see is what you get.
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