confusion of edns in dns request, get wrong response

[tangzh...@gmail.com]

custom resolver ------ google public dns ------ authoritative dns server

                                                                    A

                                                                    |

                                                                    -- tcpdump

i uesed "dig @8.8.8.8 t.ttspace.xyz" command

i think google public dns should payload custom ip in subnet of ends0, and  i used tcpdump to capture dns request packet like blow

packet 1

packet 2

why google public dns lost data of edns at somttimes,  for this reason,  i am get wrong response at custom resolver.

Best Regards

tom

[Alex Dupuy]

Google Public DNS does auto-detection of support for EDNS Client Subnet (ECS), your name server probably wasn't sending responses with ECS (even NXDOMAIN and other errors) to all queries with ECS. A common error is not to handle IPv6 addresses in ECS data when your name server is IPv4 only (clients contact Google Public DNS via IPv6 and it may resolve those queries via IPv4, or vice versa).