IPv4 vs IPv6 Explained
IPv4 uses 32-bit addresses, about 4.3 billion in total, and its free pool ran out in 2011, so networks share addresses through NAT. IPv6 uses 128-bit addresses, about 3.4 × 10^38, giving every device its own public address. Websites publish A records for IPv4 and AAAA records for IPv6, and dual-stack servers answer both.
For site owners, developers and network admins deciding whether and how to serve their website over IPv6.
knowledge
- Read time
- 2 min
- Sections
- 7
- Updated
- 14 Nov 2026
- Written by
- WebJi® team
Last editorial update: 14 November 2026.
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses, about 4.3 billion in total, while IPv6 uses 128-bit addresses, about 3.4 × 1038; IPv4's free pool is exhausted, so networks stretch it with NAT, whereas IPv6 gives every device its own public address. Both carry the same web traffic.
| Attribute | IPv4 | IPv6 |
|---|---|---|
| Standard | RFC 791 (1981) | RFC 8200 (2017; first specified 1998) |
| Address length | 32 bits | 128 bits |
| Total addresses | 4,294,967,296 | 2128 |
| Written as | 203.0.113.10 | 2001:db8::10 |
| DNS record | A | AAAA |
| Address sharing | NAT, common everywhere | Not needed |
| Auto-configuration | DHCP | SLAAC or DHCPv6 |
| Header | Variable, with checksum | Fixed 40-byte base header, no checksum |
Why did IPv4 addresses run out?
IPv4's 32 bits allow just under 4.3 billion addresses, part of which is reserved; IANA allocated its last free blocks to the regional registries in February 2011, and APNIC, which serves India, reached its final block that April. Phones, broadband and IoT devices far outnumber the remaining supply.
New IPv4 addresses now come mainly through transfers between organisations, at a market price, which is one reason hosts charge for extra IPv4 addresses. In India, IRINN, run by NIXI, is the national internet registry that allocates IP addresses under APNIC.
How are IPv6 addresses written and shortened?
An IPv6 address is eight groups of four hexadecimal digits separated by colons; leading zeros in each group can be dropped, and one run of all-zero groups can be replaced by a double colon.
| Step | Address |
|---|---|
| Full form | 2001:0db8:0000:0000:0000:ff00:0042:8329 |
| Drop leading zeros | 2001:db8:0:0:0:ff00:42:8329 |
| Compress the zero run (once only) | 2001:db8::ff00:42:8329 |
Useful special addresses: ::1 is loopback (like 127.0.0.1), fe80::/10 is link-local, and 2001:db8::/32 is reserved for documentation, which is why examples use it. In URLs an IPv6 address goes in square brackets: http://[2001:db8::10]/.
How does NAT affect websites and servers?
NAT lets many devices share one public IPv4 address, which conserves addresses but blocks unsolicited inbound connections and makes many visitors appear to come from a single IP. Mobile carriers often use carrier-grade NAT, sharing one address across many customers.
- Self-hosting: a server behind NAT needs port forwarding to be reachable over IPv4.
- Rate limits and bans: blocking one shared IPv4 address can block many innocent users.
- Logs: IPv6 visitors usually appear with distinct addresses, though privacy extensions rotate them.
- Firewalls: without NAT, an IPv6 firewall matters even more, since devices are directly addressable.
How do A and AAAA records and dual-stack work together?
An A record points a hostname to an IPv4 address and an AAAA record to an IPv6 address; a dual-stack site publishes both, and browsers try IPv6 first and fall back to IPv4 quickly using the "Happy Eyeballs" method (RFC 8305).
The trap is an AAAA record for an address the server or its firewall does not actually answer on: some visitors then wait before falling back. Only publish AAAA after the web server listens on IPv6 and the firewall allows it. DNS records are explained further in what DNS is, and you can check what a domain publishes with the DNS lookup tool.
dig A example.in +short
dig AAAA example.in +short
curl -6 -I https://example.in/ # succeeds only if IPv6 works end to end
curl -4 -I https://example.in/How do you enable IPv6 for a website on a VPS?
Get an IPv6 address or block from the provider, configure it on the network interface, make the web server listen on IPv6, allow it in the firewall, then publish the AAAA record and test from an IPv6 network. On shared hosting the provider handles this; ask support whether your account has an IPv6 address.
# 1. confirm the address is on the interface
ip -6 addr show
# 2. Nginx: add IPv6 listeners in each server block
listen [::]:80;
listen [::]:443 ssl;
# 3. UFW covers IPv6 when IPV6=yes in /etc/default/ufw (the default)
sudo ufw status verbose
# 4. after adding the AAAA record
curl -6 -I https://example.in/Allow ICMPv6 through any custom firewall rules; IPv6 neighbour discovery and path MTU discovery depend on it. Apache listens on IPv6 by default with Listen 80 on most distributions.
WebJi® VPS hosting includes a static IPv4 address; ask support@webji.services whether IPv6 is available for your server before publishing AAAA records. The full DNS setup for a new server is in pointing a domain to hosting.
Frequently asked questions
Is IPv6 faster than IPv4?
Not inherently. Speed depends on the route and network quality. IPv6 can avoid NAT translation on some mobile networks, which sometimes helps, but a well-run IPv4 path is just as fast for most websites.
Does a website need IPv6 to rank or load in India?
No. Indian networks still route to IPv4-only sites, using NAT or translation for IPv6-only devices. IPv6 support is good practice and future-proofing, not a ranking requirement, and a broken IPv6 setup is worse than none.
Can IPv4 and IPv6 devices talk to each other directly?
Not directly; they are separate protocols. Dual-stack servers answer both, and networks use translation such as NAT64 with DNS64 so IPv6-only phones can still reach IPv4-only websites.
How do I find my own IPv6 address?
Open the what is my IP tool, which shows the address your connection uses. On Windows run ipconfig, and on Linux or macOS run ip -6 addr or ifconfig. Addresses starting with fe80 are link-local and not public.
Standards per IETF RFC 791, RFC 8200 and RFC 8305; allocation dates per IANA and APNIC · Reviewed by the WebJi® team, Jaipur.
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