It seems that kinto stack doesn't have a public ipv6 DNS entry. $ host kinto.stage.mozaws.net kinto.stage.mozaws.net is an alias for 35-kinto.stage.mozaws.net. 35-kinto.stage.mozaws.net has address 52.22.124.63 35-kinto.stage.mozaws.net has address 54.165.133.164 $ host firefox.settings.services.mozilla.com firefox.settings.services.mozilla.com is an alias for d2k03kvdk5cku0.cloudfront.net. d2k03kvdk5cku0.cloudfront.net has address 54.230.79.15 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.12 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.62 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.200 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.219 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.104 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.77 d2k03kvdk5cku0.cloudfront.net has address 54.230.79.79

According to http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/elb-internet-facing-load-balancers.html#internet-facing-ip-addresses If we use a CNAME to the dualstack DNS as an entry, we should be fine.

IPV6 is not available in Default VPC with ELB, however Cloudfront now supports IPV6. I've enabled it on stage and waiting for the configuration to propagate.

I can confirm that it seems ok for settings.stage.mozaws.net $ dig AAAA settings.stage.mozaws.net ; <<>> DiG 9.10.3-P4-Ubuntu <<>> AAAA settings.stage.mozaws.net ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37057 ;; flags: qr rd ra; QUERY: 1, ANSWER: 9, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 65494 ;; QUESTION SECTION: ;settings.stage.mozaws.net. IN AAAA ;; ANSWER SECTION: settings.stage.mozaws.net. 300 IN CNAME d1bzcju3y699vy.cloudfront.net. d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:d800:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:ca00:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:b600:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:b400:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:a000:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:9a00:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:2e00:2:3976:1380:93a1 d1bzcju3y699vy.cloudfront.net. 59 IN AAAA 2600:9000:2007:a00:2:3976:1380:93a1 ;; Query time: 44 msec ;; SERVER: 127.0.0.53#53(127.0.0.53) ;; WHEN: Tue Jan 30 11:15:10 CET 2018 ;; MSG SIZE rcvd: 318 But not yet for prod: $ dig AAAA firefox.settings.services.mozilla.com ; <<>> DiG 9.10.3-P4-Ubuntu <<>> AAAA firefox.settings.services.mozilla.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27186 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 65494 ;; QUESTION SECTION: ;firefox.settings.services.mozilla.com. IN AAAA ;; ANSWER SECTION: firefox.settings.services.mozilla.com. 71 IN CNAME d2k03kvdk5cku0.cloudfront.net. ;; Query time: 15 msec ;; SERVER: 127.0.0.53#53(127.0.0.53) ;; WHEN: Tue Jan 30 11:15:59 CET 2018 ;; MSG SIZE rcvd: 109