Question 1

Why did the internet run out of IPv4 addresses, and how are they traded now?

Accepted Answer

Because the address space was fixed at **32 bits — about 4.3 billion addresses — in 1981**, when the internet was a research network and nobody expected every household to hold dozens of connected devices. The pool of unallocated addresses was exhausted over the 2010s, and what exists now is a **secondary market** in addresses already allocated.

**Why 4.3 billion was never really 4.3 billion.** Large blocks were handed to early adopters — universities, corporations, government agencies — in sizes far beyond their needs, under a classful allocation scheme with very coarse granularity. Substantial ranges are also reserved and unusable. The effective supply was always materially smaller than the theoretical one.

**What delayed exhaustion:**

**CIDR**, replacing rigid class boundaries with arbitrary prefix lengths, so allocations could match actual need.

**NAT**, letting an entire network share one public address — the single biggest factor, and the reason exhaustion took decades rather than years.

**Reclamation** of unused legacy blocks.

**What happened when the registries ran dry.** Each RIR reached its final allocation phase and moved to strict rationing, typically a single small block per new member. **A transfer market then formed**: addresses are bought and sold, with the registry recording the change, and prices per address rose from a few dollars into the tens.

**This has real consequences.** Address space became a **balance-sheet asset**; large holders monetised legacy allocations; and new entrants face a cost incumbents never paid, which is a genuine barrier to competition.

**The knock-on effects you experience:**

**CGNAT**, where an ISP shares one public address among many subscribers, breaking inbound connections and confusing geolocation and abuse attribution.

**Reputation contamination**, where one bad actor on a shared address affects everyone on it.

**IPv6** is the actual solution and deployment continues to climb, but dual-stack operation means IPv4 retains value for as long as any significant destination remains v4-only.

Question 2

What is CGNAT, and why does it break things?

Accepted Answer

Carrier-grade NAT is a technique ISPs use to share a single public IP address between many customers — a response to IPv4 address exhaustion, and a cause of a specific and confusing set of problems.

Question 3

What is NAT, and why does every home network use it?

Accepted Answer

Network Address Translation lets many devices share one public IP address, by rewriting addresses and ports as traffic passes through the router. Why it exists. IPv4 provides around 4.3 billion

Question 4

What is anycast, and how can one IP address be in many places?

Accepted Answer

Anycast announces the same IP address from multiple locations, and the routing system naturally delivers each user's traffic to whichever location is closest in network terms. It is one of the more

Question 5

Who actually runs the internet?

Accepted Answer

Nobody, and several bodies with narrow remits — which is the accurate answer rather than an evasive one. There is no central authority; there are institutions that coordinate specific scarce

Question 6

What is the difference between a static and a dynamic IP address?

Accepted Answer

Whether your public address stays the same or changes periodically — and for most people it matters far less than it sounds, until it suddenly matters a great deal. Dynamic. Your ISP assigns an

Question 7

What is the last mile problem?

Accepted Answer

The final connection from a network's local distribution point to each individual building is disproportionately expensive, and that single fact shapes almost everything about broadband availability,

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