During a discussion on the NANOG list today about IPv6 deployment/migration, I came up with a way to test how many of your websites’ viewers can reach you on IPv6, and who would have problems if you turned AAAA records on.
Basically, drop 3 image tags in to your site:
Set the “onerror” for these images to change the src to:
Another good idea is to have the onerror event set onerror to ”, so it doesn’t loop if it can’t get to your main site for some weird reason.
These images should all be 1×1 transparent gifs. That’s a whopping 43b filesize, so don’t worry about bandwidth.
Comparing the hits against these 6 images should tell you roughly who’ll break if you turn on AAAA records.
Further work and things for me to try:
- Set timers to start on page load, and stop on load of each of those images, and then POST it.
- Check network traffic to addresses that the image URLs point to, and analyse it against logs. Points of interest are connections that don’t fully open, and requests that don’t arrive.
- Put many images in, with long URLs, so upstream MTU can be tested.
- Have those images vary in size, so downstream MTU can be tested.