Jumping on the IPv6 Express

I have started configuring my web sites to work with IPv6.

The Slowest Rollout in Internet History

The transition to IPv6 (with 128-bit addresses) is going slowly. So slowly that there are still wiki pages enumerating IPv6-enabled web sites.

This is because of various things, one of which, described in this ten-year-old memo, is that all computers connected to the public Internet need to be reconfigured to have an IPv6 address in addition to its existing IPv4 address, and until that day, no-one can manage without an IPv4 address. This means there is no benefit in terms of relieving the shortage until every sysadmin has upgraded every server. This makes it hard to motivate people to meddle with their already-working servers, especially as patchy provision meant some customers may lose access to your site when you do (see IPv6 brokenness and DNS whitelisting).

Having said that, peer pressure is a wonderful thing, and it turns out that even boiling the ocean has to succeed as a strategy eventually. According to CISCO, 30% of the WWW is now accessible via IPv6.

My Migration So Far

Lucky for me, Linode and Gandi are hip to IPv6, so once I knew what I had to do it was relatively straightforward to set things up.

The problem is, knowing what to do was a problem. It took me a long time to find information on what steps I actually needed to perform: while there are myriad web sites bewailing the imminent exhaustion of the address space and exhorting action, there are vanishingly few on what concrete steps someone who just happens to be running a web server should do. So here is what I did.

First, Linode have an option to add an IPv6 address automatically: you just reboot and your server wakes up with an extra address on its network device. (The extra reboot was also a chance for me to learn which of my servers were still not configured to restart automatically.)

Now on my Linode dashboard I learn that one of my Public IPs is 2a01:7e00::f03c:91ff:fe96:cabf/64. The /64 confused me (were they implying I had an entire /64 subnet?) until my lodger told me to ignore it.

It turns out the configuration change to Nginx is fairly small: you change this:

listen 80;

to this:

listen [::]:80;

This says to listen to all IPv6 addresses (denoted by the special address ::). GNU/Linux networking automagically embeds IPv4 so that someone connecting from would appear to Nginx to be connecting from ::ffff:

Now all that remained was to edit the zone files (hosted on Gandi in my case) to add at least three new records per site:

@ 10800 IN AAAA 2a01:7e00::f03c:91ff:fe96:cabf
ip4 10800 IN A
ip6 10800 IN AAAA 2a01:7e00::f03c:91ff:fe96:cabf

The first adds the new address as an alternative for the domain. All the existing A records should also have a corresponding AAAA record added. The second two are synonyms that only have the IPv4 or IPv6 address associated with them (for testing, mostly). For example, I am updating my Nginx configuration so that ip4.spreadsite.org and ip6.spreadsite.org are alternative names for spreadsite.org. You only need to use them if you want to force routing over a particular IP version.

Validation and Verification

The final step was finding a way to test the results, since my ISP does not yet support IPv6 for customers, so I can’t just connect to my site and see what happens. One way is IPV6 Test, which checks the AAAA record is present and the site can be contacted, but it can only check it is accessible from its location.

The other encouraging sign that it is working is I now see Google’s bot crawling my site from an IPv6 address.