A long time ago, when our provider offered the possibility running an IPV6-over-IPV4 tunnel, I spent some time configuring this.
To be able to use a tunnel, I had to use the website of the provider to configure their part; our part was just the activation of a tunnel interface. This tunnel encapsulates IPV6 in IPV4 and delivers the packets to a host which has a native IPV6 connection to the Internet. Setting DNS accordingly I could complete the IPV6 tests on the Internet and access my own website from external via just IPV6.
Then, when the techniques progress, we were able to migrate from a DSL connection to fiber. Besides getting more bandwitdh, there would be little difference between up/download and – far more important – distance to the POP would not matter anymore, compared to DSL. Even better, the provider would supply a modem which would run native IPV6.
After the installation and the setup, the modem was configured and tested. All set, migration from the DSL connection to the new modem (and new Internet-IP) was done. Biggest challenge is how to ensure the DNS resolves promptly to the new address. Especially for mail, as little problems as possible.
With a fully migrated connection, time to run IPV6. And then?
Searching the Internet resulted in many hits ‘autoconfig works fine’ and ‘no issues, I can run IPV6 using autoconfig’. However, with a server running websites and mail, there is ample time to reconfigure the network to use autoconfig. And yes, if the main server depends on its ip configuration, modifying its networkconfiguration to autoconfig might result in connection problems. Therefore, manual change is required to ensure stability and availability of this machine.
Autoconfig works fine, and I can’t use autoconfig. The webinterface to the modem only returns the prefix handed by the provider; prefixes don’t make the network address. What’s next?
Quickest was to use a laptop with autoconfig enabled, which indeed got an IPV6 address. Using the traceroute6 ipv6.google.com, it will show the IPV6 address of the default gateway. From this ip address, the network could be derived, thus able to configure the IP addres manually on the server.
The needed configuration was added on the /etc/network/interfaces files easily – restart networking and yes: Connectivitiy on IPV6…