IPv6 was designed to replace IPv4 once its 4.3 billion addresses ran out, and in 2026 about half of the users reaching Google do so over IPv6. The other half, and many services, still need IPv4, which the registries have all but run out of: IPv6 comes with a registry membership at little or no extra cost, while IPv4 now comes by transfer, by lease or from a waiting list. So most networks run both.
The technical differences
| IPv4 | IPv6 | |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Written as | 192.0.2.1 | 2001:db8::1 |
| Addresses in all | About 4.3 billion | About 3.4 × 10^38 |
| A site usually gets | A few public addresses, the rest private behind NAT | A /48: 65,536 subnets of /64 |
| Header | 20 to 60 bytes, with a checksum | A fixed 40 bytes, extension headers, no checksum |
| Fragmentation | By routers and by the sending host | By the sending host only |
| Address setup | DHCP or by hand | Automatic (SLAAC), DHCPv6 or by hand |
| Finding a neighbor's hardware address | ARP | Neighbor Discovery, over ICMPv6 |
| DNS records | A, with reverse DNS under in-addr.arpa | AAAA, with reverse DNS under ip6.arpa |
| Smallest block routed on the internet | A /24, by common practice | A /48, by common practice |
The definitions are in RFC 791 for IPv4 and RFC 8200 and RFC 4291 for IPv6, with automatic setup in RFC 4862.
What the registries hand out, and at what cost
| IPv4 | IPv6 for a member | |
|---|---|---|
| The RIPE NCC | One /24 per LIR account, from a waiting list: 799 LIRs, the first waiting 480 days on 16 October 2026; no extra accounts for now (since 29 September 2026) | A /32, up to a /29, included in the yearly fee of €1,800 |
| ARIN | Up to a /22 from a waiting list it fills each quarter, for organizations holding no more than a /20 | A /32, or a /36 or /40 on request; a /32 alone means $1,100 a year in 2026 |
| APNIC | Up to a /23 in total per account, from its last 0.18 of a /8 | A /32; with a /24 of IPv4, AUD 2,256 a year in 2026 |
Beyond what the registries hand out, IPv4 is bought and leased. How the registries ran out is in IPv4 exhaustion explained. The three registries compared on every point are in the RIPE NCC, ARIN and APNIC compared.
How far IPv6 has spread
- About half of Google's users. The share of users reaching Google over IPv6 first passed 50% on 28 March 2026, at 50.10%, by Google's own measurement as the Internet Society reported it.
- Very different by country. On Google's per-country figures of 15 October 2026: France 87%, Saudi Arabia 69% and India 67%, against Italy 19% and Spain 13%.
- Most registry members hold IPv6. On 30 June 2026, 76% of the RIPE NCC's members held IPv6, 70% of APNIC's and 49% of ARIN's.
Google's figure counts connections to Google only; other measurements, on other traffic, come out lower.
Why networks still need IPv4
- Half the users connect over IPv4 only. A service reachable only over IPv6 misses them, unless their own network translates for them.
- Partners and services expect it. Allowlists, firewall rules, mail reputation and many APIs are still set up for IPv4 addresses.
- Clouds charge for it. Public IPv4 addresses at the large clouds cost by the hour, which is why some bring their own (cloud IPv4 costs and BYOIP).
Running both
- Dual stack, both protocols on every interface, is the usual way.
- IPv6-only networks reach IPv4 services through NAT64 and DNS64 (RFC 6146, RFC 6147), and mobile networks often through 464XLAT (RFC 6877).
- Providers stretch IPv4 with carrier-grade NAT, sharing one public address among many customers.
- Each protocol needs its own care: firewall rules, monitoring and reverse DNS for both, and a blocklist check for IPv4 and IPv6 alike.
Where RTM Networks fits
We lease, buy and sell IPv4, and lease IPv6 for networks that would rather not hold their own: see leasing IPv6. Independent IPv6 of your own comes through our PI and ASN sponsorship, and which of PI, PA or a lease fits is in IPv6: PI, PA or lease.
Contact
Een IPv6-toewijzing nodig?
Vertel ons welke omvang u nodig heeft, vanaf een /48, en hoe u die wilt routeren. Wij reageren meestal in 1-3 kantooruren.
