In a real-world scenario, 6to4 tunneling requires a public IPv4 address because the tunnel needs to be reachable by other routers on the open internet.
However, in this lab environment (and most home networks), we are behind NAT, meaning our internal IP address (like 172.16.50.199) is private.
We use a conceptual IP (192.0.2.1) for several important reasons:
- Simulation of Reality: Since private IPs cannot be used to generate valid 6to4 addresses, using a conceptual public IP allows you to practice the actual configuration steps and math (like converting to hexadecimal) as if you had a real public connection.
- Safety (RFC 5737): The address
192.0.2.1belongs to a special block reserved exclusively for documentation and examples. By using it, we ensure that our lab configuration won't accidentally interfere with real traffic or real servers on the internet. - Predictability: Using a fixed placeholder address makes it easier for the lab instructions to show you exactly what your output should look like, ensuring you can follow along without getting lost in varying numbers.
Summary: We use it as a "stunt double" for a real public IP so you can learn the setup process safely and correctly!
