IPv6 6to4 Translator

Translate IPv4 ↔ IPv6 using 6to4 prefix (2002::/16).

About This Tool

The 6to4 IPv6 Address Translator converts between public IPv4 addresses and their 6to4 IPv6 representations using the 2002::/16 prefix. 6to4 (RFC 3056) is an automatic IPv6 tunneling mechanism that was designed to help IPv4 sites adopt IPv6 during the transition period. Each public IPv4 address corresponds to a /48 IPv6 prefix under 2002::/16, formed by embedding the IPv4 address in hexadecimal. While 6to4 is now considered deprecated in favor of newer mechanisms, understanding it remains important for legacy network analysis and historical context.

How to Use

Select translation mode: IPv4 → 6to4 or 6to4 → IPv4
For IPv4 to 6to4: Enter a public IPv4 address (e.g., 192.0.2.1)
The tool will show the corresponding /48 6to4 prefix (e.g., 2002:c000:0201::/48)
For 6to4 to IPv4: Enter a 6to4 IPv6 address starting with 2002::
Click "Translate" to perform the conversion
The extracted IPv4 address will be displayed
Note: Only public IPv4 addresses should be used with 6to4 (not RFC 1918 private addresses)

Features

Bidirectional 6to4 address translation
Converts IPv4 to 2002::/16 prefix format
Extracts IPv4 from 6to4 IPv6 addresses
Shows complete /48 6to4 prefix allocation
Validates 2002:: prefix for IPv6 input
RFC 3056 compliant conversion
Clear error messages for invalid inputs
Supports both compressed and expanded IPv6 formats

Common Use Cases

Understanding legacy 6to4 tunneling deployments
Analyzing historical IPv6 transition mechanisms
Debugging 6to4 relay issues in older networks
Converting addresses in legacy documentation
Educational purposes: learning IPv6 transition history
Analyzing packet captures with 6to4 addresses
Understanding why 6to4 was deprecated
Migrating from 6to4 to modern IPv6 mechanisms
Network archaeology and legacy system analysis
Security research on deprecated IPv6 mechanisms

Technical Details

6to4 is an automatic tunneling mechanism that embeds a public IPv4 address within an IPv6 address using the 2002::/16 prefix. Each IPv4 address gets a corresponding /48 IPv6 prefix.

Address Format:

Prefix: 2002 (16 bits)
IPv4 in hex: Next 32 bits (8 hex digits)
Subnet ID: 16 bits (typically :0000: or customizable)
Interface ID: Last 64 bits

Translation Example:

IPv4: 192.0.2.1
Hex: C0 00 02 01 → c000:0201
6to4 Prefix: 2002:c000:0201::/48
Example Address: 2002:c000:0201::1

How 6to4 Worked:

Site with public IPv4 gets automatic /48 IPv6 prefix (2002:xxxx:xxxx::/48)
6to4 router encapsulates IPv6 packets in IPv4 for transit over IPv4 Internet
6to4 relay routers (anycast 192.88.99.1) forward to native IPv6 Internet
No explicit tunnel configuration or broker registration needed

Why 6to4 is Deprecated (RFC 7526):

Unreliable relays: Anycast relay approach led to poor performance and reachability
No security: Anyone could announce 6to4 relay, enabling man-in-the-middle attacks
Asymmetric routing: Outbound and inbound paths often used different relays
NAT incompatible: Required public IPv4 address, broke behind NAT
Difficult troubleshooting: Users couldn't control which relay was used

Modern Alternatives:

Native IPv6: Direct IPv6 connectivity without tunneling
NAT64/DNS64: For IPv6-only networks accessing IPv4 resources
464XLAT: Mobile network IPv6 transition
Tunnel Brokers: Managed tunnels with reliable endpoints (Hurricane Electric, etc.)

Historical Significance:

6to4 was one of the first widely deployed IPv6 transition mechanisms and helped early IPv6 adoption. However, its automatic nature led to connectivity issues that harmed IPv6 deployment, leading to its deprecation. Operating systems now disable 6to4 by default or have removed it entirely.

6to4 Prefix Recognition:

Any IPv6 address starting with 2002: is a 6to4 address. If you see these in logs or packet captures, it indicates legacy transition infrastructure that should ideally be migrated to modern IPv6 connectivity.