About 4 years ago, I published a quick diary summarizing our experience with IPv6 at the time [1]. Back then, the IPv6 traffic to our site was miniscule. 1.3% of clients connecting to our server used IPv6. Since then, a lot has changed in IPv6. Comcast, one of the largest US ISPs and an IPv6 pioneer now offers IPv6 to more then 25% of its users [2] . Many mobile providers enable IPv6, and more users access our site from mobile devices then before. So I expected a bit of an increase in IPv6 traffic. Lets see what I found.

The short summary is: We do see A LOT more IPv6 traffic, but auto-configured tunnels pretty much went away (probably a good thing)

Overall, the number of IPv6 clients multiplied by about 3 and about 4% of requests received by our web server now arrive via IPv6. Given that we use a tunnel and proxy at this point to provide IPv6 access, we can only assume that there are more IPv6 capable clients out there but technologies like "happy eyeballs" make them prefer IPv4.

The difference is even more significant looking at tunnels. 6-to-4 tunnels only make up 0.3 % of all IPv6 requests, and Terredo is not significant (only about 100 requests total for all of last month). 2001::/16 remains the most popular /16 prefix, but 2002::/16 which was #2 in 2010 no longer shows up.

Within 2001::/16, Hurricane Electric (2001:470::/32) still dominates, indicating that we still have a lot of tunnels. But it is now followed by 2607:f740::/32 (Host Virtual) , 2401:c900::/32 (Softlayer) , 2a01:7a0::/32 (Velia) and 2607:f128::/32 (Steadfast). 

As far as reverse DNS resolution goes, still only very few ISPs appear to have it configured for IPv6. 

[1] https://isc.sans.edu/diary/IPv6+and+isc.sans.org/7948
[2] http://www.comcast6.net

and of course our IPv6 Security Essentials class. 

------
Johannes B. Ullrich, Ph.D.
SANS Technology Institute
Twitter