What is a 6to4 prefix?

6to4 (RFC 3056) uses the reserved prefix `2002::/16` followed by the 32 bits of a public IPv4 address in hex to construct an automatic 48-bit IPv6 subnet.

Updated: August 2026 • Verified v1.2

IPv4 to IPv6 Mapping & 6to4 Converter

Internet & NetworkNetwork

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Mapping Synthesis: [a.b.c.d] ➔ [::ffff:hex(a,b):hex(c,d)] & [2002:hex(a,b):hex(c,d)::/48]

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Understanding Your Results

Calculates RFC 4291 dotted and hex IPv4-mapped IPv6 representations (`::ffff:192.0.2.1` and `::ffff:c000:0201`), RFC 3056 6to4 prefix (`2002:c000:0201::/48`), and legacy formats.

Practical Guidance & Next Steps

IPv4-mapped IPv6 addresses are used by dual-stack operating systems to represent IPv4 endpoints inside standard IPv6 sockets.

What is this?

A network engineering utility that translates 32-bit IPv4 addresses into standard 128-bit IPv6 transition notations.

How does it work?

1. Enter an IPv4 address (e.g. 192.0.2.1) or pick a preset. 2. View IPv4-mapped IPv6 (dotted & hex) and 6to4 prefix mappings. 3. Copy the exact format in 1 click.

Why use it?

Quickly builds dual-stack socket addresses, firewall rules, and transition tunnel configurations.

Technical Scope & Calculation Limitations

Calculates standard transition and mapping representations for valid IPv4 unicast addresses.

Frequently Asked Questions

Defined in RFC 4291, an IPv4-mapped address (format `::ffff:a.b.c.d` or `::ffff:xxyy:zzww`) allows dual-stack network software to handle IPv4 traffic using standard IPv6 socket structures.

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