2.7. IPv4 Network Addressing

💡 First Principle: Every device on an IP network needs a unique address within its scope. Private addresses (RFC 1918) are reusable within organizations but not routable on the internet. Public addresses are globally unique but scarce—hence NAT for address conservation and IPv6 for long-term solution.

What breaks without proper addressing? Assign duplicate IPs, and both devices experience intermittent connectivity as ARP tables flip between them. Use public addresses internally, and you'll either conflict with real owners or waste scarce resources. Misconfigure subnet masks, and devices think remote hosts are local (or vice versa)—traffic goes to the wrong place.

Think of IP addressing like phone numbers: public IPs are like real phone numbers (globally unique, dialable from anywhere). Private IPs are like internal extensions (unique within your building but require the receptionist—NAT—to reach outside).