-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Following up on a two year old thread, one of my clients just hit this problem. The failure is not that www.pay.gov is not reachable over ipv6 (2605:3100:fffd:100::15). They accept (TCP handshake) the port 443 connection, but the connection then hangs waiting for the TLS handshake. openssl s_client -connect www.pay.gov:443 openssl s_client -servername www.pay.gov -connect 199.169.192.21:443 Browsers (at least firefox) see that as a very slow site, and it does not trigger their happy eyeballs fast failover to ipv4. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (GNU/Linux) iEYEAREKAAYFAlgrjDEACgkQL6j7milTFsG8OwCgh5yRxxZHskjL4HVhzxIEmenA LQgAniRMcYf/DIcg+8ve55MxUgrUbmzC =MS8j -----END PGP SIGNATURE-----