IPv4 vs IPv6: What's the Difference?

The internet runs on two versions of the Internet Protocol: IPv4, which has been in use since 1981, and IPv6, its successor designed to solve the address exhaustion crisis. Both coexist today, but the transition to IPv6 is ongoing and accelerating.

IPv4: The Original

IPv4 uses 32-bit addresses written in dotted decimal notation: four octets separated by dots, like 8.8.8.8. This gives approximately 4.3 billion possible addresses. IPv4 was designed when the internet was a research network connecting a handful of universities — nobody anticipated billions of connected devices.

The global IPv4 address pool was officially exhausted in 2011 when IANA allocated the last blocks to the Regional Internet Registries. Today, organizations acquire IPv4 addresses through transfers (buying from existing holders) at prices of $30-50+ per address.

IPv6: The Future

IPv6 uses 128-bit addresses written in hexadecimal, separated by colons: 2606:4700::1111. This provides 340 undecillion addresses (3.4 x 10³⁸). IPv6 was standardized in 1998 (RFC 2460) and is designed to be the long-term replacement for IPv4.

Key differences from IPv4:

• Address space — Virtually unlimited addresses, eliminating the need for NAT in most cases
• Header simplification — The IPv6 header is simpler and fixed-length, allowing faster processing by routers
• No broadcast — IPv6 uses multicast and anycast instead, reducing unnecessary network traffic
• Built-in autoconfiguration — Devices can automatically configure their own addresses using SLAAC (Stateless Address Autoconfiguration)
• IPsec support — Encryption support was designed into the protocol from the start

IPv6 in BGP

BGP carries both IPv4 and IPv6 routing information. The global routing table contains over a million IPv4 prefixes and a growing number of IPv6 prefixes. Major networks like Google, Cloudflare, and Meta fully support IPv6.

When you look up an address in the looking glass, the result shows whether it is IPv4 or IPv6 with a badge. You can explore both types:

• 8.8.8.8 — Google DNS (IPv4)
• 2606:4700::1111 — Cloudflare DNS (IPv6)
• 2001:4860:4860::8888 — Google DNS (IPv6)

Adoption Status

As of 2025, roughly 40-45% of global internet traffic uses IPv6, with significant variation by country. India, France, Germany, and the United States lead in adoption. Many mobile networks are IPv6-only, using translation mechanisms (NAT64/DNS64) to reach IPv4-only services.

You can check any autonomous system to see how many IPv4 vs IPv6 prefixes it announces — the looking glass shows them separately.