IPv4 Address Exhaustion: Causes and Solutions
Understand why the 4.3 billion IPv4 addresses ran out, the timeline of exhaustion, and the technologies extending IPv4's life.
The Scale of the Problem
IPv4 uses 32-bit addresses, providing a theoretical maximum of 4,294,967,296 (about 4.3 billion) unique addresses. In 1981 when IPv4 was standardized, 4.3 billion seemed inexhaustible. By 2025, there are over 15 billion internet-connected devices worldwide -- more than three times the total IPv4 address space.
Several factors accelerated exhaustion beyond just device count:
- Wasteful early allocation -- Organizations received entire /8 blocks (16.7 million addresses). MIT, Apple, and the US Department of Defense each hold a /8.
- No recycling mechanism -- Once allocated, addresses were rarely returned.
- Internet of Things -- Billions of sensors, cameras, and smart devices each need network connectivity.
Exhaustion Timeline
| Date | Event |
|---|---|
| Feb 2011 | IANA allocates the last five /8 blocks to RIRs |
| Apr 2011 | APNIC (Asia-Pacific) reaches its last /8 |
| Sep 2012 | RIPE NCC (Europe) reaches its last /8 |
| Jun 2014 | LACNIC (Latin America) reaches its last /10 |
| Sep 2015 | ARIN (North America) exhausts free pool completely |
| Jan 2020 | RIPE NCC exhausts remaining addresses entirely |
AFRINIC (Africa) was the last RIR with available space, but it too has severely limited availability.
Technologies Extending IPv4
NAT and CGNAT
Network Address Translation allows thousands of devices to share a single public IP. Carrier-Grade NAT (CGNAT) adds a second layer, with ISPs sharing public IPs among multiple customers. While effective, CGNAT breaks some applications and makes it impossible to host services without additional configuration.
IPv4 Address Market
Organizations buy and sell IPv4 address blocks on a secondary market:
- Prices ranged from $25-60 per IP in recent years.
- Brokers like IPv4.Global and Hilco Streambank facilitate transfers.
- RIRs must approve transfers to update WHOIS records.
IPv6 Deployment
The long-term solution is IPv6, which provides 340 undecillion addresses (2^128). IPv6 adoption has grown steadily, with Google reporting over 45% of its traffic arriving over IPv6. However, full transition will take many more years.
Why Full Transition Takes So Long
- Dual-stack cost -- Organizations must run IPv4 and IPv6 simultaneously during transition.
- Legacy systems -- Many embedded devices, industrial systems, and older software only support IPv4.
- ISP investment -- Upgrading infrastructure requires significant capital expenditure.
- "Good enough" workarounds -- NAT and CGNAT keep IPv4 functional, reducing urgency to migrate.
What This Means for You
If you run a network, planning for IPv6 is no longer optional. New address allocations from RIRs are IPv6-only in most regions. For existing IPv4 infrastructure, expect CGNAT to become more common, potentially affecting VPN connections, gaming, and self-hosted services.