IPIPv4 to IPv6 Converter
Convert any IPv4 address to all its IPv6 representations: IPv4-mapped (::ffff:192.168.1.1), IPv4-compatible (deprecated), 6to4 (2002:c0a8:0101::), NAT64 prefix (64:ff9b::), and the full 128-bit expanded format. Includes a complete guide to IPv6 transition mechanisms.
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What Is IPv4 to IPv6 Conversion?
IPv4 to IPv6 conversion maps an IPv4 address into one of several standard IPv6 representations. This is necessary because the internet is in a long transition from IPv4 (32-bit, ~4.3 billion addresses) to IPv6 (128-bit, 340 undecillion addresses). During this transition, mechanisms exist to represent IPv4 addresses within the IPv6 address space — allowing dual-stack systems, tunnelling protocols, and translation gateways to handle both address families.
IPv4 and IPv6 coexist during the transition period — IPv4 addresses can be embedded within IPv6 to allow interoperability between the two protocol versions
Types of IPv4-in-IPv6 Representations
| Representation | Format | Example (192.168.1.1) | Purpose & RFC |
|---|---|---|---|
| IPv4-Mapped IPv6 | ::ffff:a.b.c.d | ::ffff:192.168.1.1 | RFC 4291 §2.5.5.2 — Most common. Dual-stack OS sockets represent incoming IPv4 connections in this format. Python socket.getpeername() on an IPv6 socket returns this. |
| IPv4-Mapped (hex) | ::ffff:xxyy:zzww | ::ffff:c0a8:0101 | Same as above in compact hex notation. Used in routing tables, low-level debug output. |
| IPv4-Compatible IPv6 | ::a.b.c.d | ::192.168.1.1 | RFC 4291 §2.5.5.1 — Deprecated (RFC 4291). Used in early IPv6 transition mechanisms. Modern systems should not use this format. |
| 6to4 Address | 2002:xxyy:zzww::/48 | 2002:c0a8:0101::/48 | RFC 3056 — Automatic tunnelling. An IPv4 address embedded in a /48 prefix beginning with 2002::. Allows IPv6 over IPv4 networks without tunnel configuration. Deprecated but still seen in legacy networks. |
| Teredo Address | 2001::/32 + IPv4 | 2001:0000:c0a8:0101:… | RFC 4380 — Tunnelling through NAT. Embeds IPv4 server and client addresses in a specific 128-bit structure. Used by Windows for IPv6 connectivity through NAT. Still used in Windows networks. |
| Full IPv6 128-bit | ::ffff:0:a.b.c.d | ::ffff:0:192.168.1.1 | RFC 6052 — NAT64 prefix. Used by NAT64 gateways to represent IPv4 destinations in an IPv6-only network. |
IPv4-Mapped IPv6 in Practice — The Most Important Format
The IPv4-mapped IPv6 format (::ffff:x.x.x.x) is the one you will encounter most in programming. When a server application binds to an IPv6 socket (socket.AF_INET6), it can receive connections from both IPv4 and IPv6 clients — the operating system automatically represents IPv4 client addresses as IPv4-mapped IPv6 addresses:
import socket
server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
server.bind(('::', 8080))
server.listen()
conn, addr = server.accept()
print(addr) # ('::ffff:192.168.1.100', 54321, 0, 0)
# IPv4 client shown as mapped IPv6
# Extract real IPv4:
real_ip = addr[0].replace('::ffff:', '') # '192.168.1.100'
# Node.js — same issue:
server.on('connection', socket => {
let ip = socket.remoteAddress;
if (ip.startsWith('::ffff:')) ip = ip.slice(7); // strip mapping
console.log(ip); // '192.168.1.100'
});
The 6to4 Transition Mechanism
6to4 (RFC 3056) was one of the first automatic IPv6 transition mechanisms. Any organisation with a public IPv4 address could automatically get an IPv6 /48 prefix by embedding their IPv4 address in the 2002::/16 prefix. For example, a server at 203.0.113.1 would get the 6to4 prefix 2002:cb00:7101::/48 (2002 + hex(203)=CB + hex(0)=00 + hex(113)=71 + hex(1)=01).
While 6to4 is deprecated (the anycast relays were unreliable), understanding it helps explain why you might see 2002:: prefixes in older network configurations or routing tables. The format is still used in some legacy enterprise networks that haven't completed their IPv6 migration.
IPv6 Transition Mechanisms — Complete Overview
The IETF has defined several mechanisms to ease the transition from IPv4 to IPv6. Understanding them puts the IPv4-to-IPv6 conversions in context:
| Mechanism | RFC | Status | How It Works |
|---|---|---|---|
| Dual-Stack | RFC 4213 | ✓ Current standard | Hosts run both IPv4 and IPv6 simultaneously. Preferred for new deployments — no translation needed. |
| IPv4-Mapped (::ffff:) | RFC 4291 | ✓ Active | OS represents IPv4 connections on IPv6 sockets. Transparent to application code. |
| NAT64 + DNS64 | RFC 6146/6147 | ✓ Active for IPv6-only networks | Translates IPv6 packets to IPv4 at the network edge. Allows IPv6-only clients to reach IPv4-only servers. Used by Jio, mobile networks. |
| 6to4 | RFC 3056 | ⚠ Deprecated | Tunnels IPv6 over IPv4 using 2002::/16 prefix. Unreliable due to anycast relay issues. |
| Teredo | RFC 4380 | ⚠ Legacy, still in Windows | IPv6 tunnelling through IPv4 NAT. Still active on Windows machines behind NAT. |
| ISATAP | RFC 5214 | ⚠ Deprecated | Intra-site tunnelling. Embeds IPv4 address as last 32 bits of IPv6 address. |
| 464XLAT | RFC 6877 | ✓ Active (mobile) | Combination of CLAT (client-side) and PLAT (provider-side NAT64). Used in mobile networks including Jio for IPv6-only access networks. |