<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <div class="moz-cite-prefix">On 25/03/2024 10:06, Thomas Schäfer wrote: </div> <blockquote type="cite" cite="mid:2889835.xIfCSIpeF9@witz"> <pre>I can't present, but I would suggest the topic: Lessons learned/ Lessons not learned - the mess with mapped IPv4 addresses - or just Layer 8 problems: Lessons learned: <a class="moz-txt-link-freetext" href="https://www.githubstatus.com/incidents/5y8b8lsqbbyq" moz-do-not-send="true">https://www.githubstatus.com/incidents/5y8b8lsqbbyq</a> Lessons not learned: united by Postbank/Deutsche Bank, new relic, ns1, ibm, fastly and others <a class="moz-txt-link-freetext" href="https://forum.newrelic.com/s/hubtopic/aAX8W0000015BUvWAM/bamnrdatanet-resolves-with-wrong-aaaarecords" moz-do-not-send="true">https://forum.newrelic.com/s/hubtopic/aAX8W0000015BUvWAM/bamnrdatanet-resolves-with-wrong-aaaarecords</a> </pre> </blockquote> Hey Thomas, I think this is a great topic and somebody should definitely cover it. I remember setting up a couple of test sites to prove wrong the claim: "We use IPv4-mapped AAAA records in order to save money on our authoritative DNS provider who charges us per query." <a class="moz-txt-link-freetext" href="https://ipv4-mapped.0skar.cz/">https://ipv4-mapped.0skar.cz/</a> - this has only IPv4-mapped AAAA record - should be unreachable <a class="moz-txt-link-freetext" href="https://ipv4-mapped-pref.0skar.cz/">https://ipv4-mapped-pref.0skar.cz/</a> - this is "Postbank-style" dual stack with A and IPv4-mapped AAAA record - everybody should reach the A record website However, my macOS 14.4 on IPv6-only network happily connect to both test sites from all browsers and even prefers IPv4-mapped AAAA over A records. So the aforementioned claim may not be completely wrong (though it is still stupid). Any volunteer willing to try common OS behaviour while counting the number of DNS queries? :) -- Best regards, Ondřej Caletka RIPE NCC </body> </html>