Opening Scenario
You're debugging a service issue. You look at a request log and see the client IP: 192.168.1.45. You try to geolocate it or block it — nothing works. You look up the IP — it's listed as a private address that doesn't exist on the public internet. You realize: that's not the user's real IP. Something replaced it. Half of your production IP logging is probably wrong.
Question Progression
1. Why do private IP addresses exist?
Question: IPv4 has about 4.3 billion addresses. The internet has far more than 4.3 billion connected devices. How is this possible, and what does that mean for how your devices are actually addressed?
Reasoning: IPv4 addresses were designed in the 1970s when 4.3 billion seemed sufficient. By the early 1990s it was clear they'd run out. Rather than immediately deploying IPv6, the internet engineering community defined private address…
In the full tutorial
- Closing: When to Reach for This