RIPE Atlas Web site displays a lot of "undefined" for the tests in AS 3125. See for instance <https://atlas.ripe.net/measurements/22766270/#!probes> or <https://atlas.ripe.net/measurements/22766942/#!probes> But the DNS resolution from this AS seems to work. Checking the raw results in JSON, I see that we have a lot of failures on one IPv6 resolver: "dst_name": "fe80::a63e:51ff:fe77:e26", "error": { "socket": "connect failed Invalid argument" }, We do not see such IPv6 problem in other AS (see for instance <https://atlas.ripe.net/measurements/22766995#!probes>) I assume that the "connect failed Invalid argument" is the fault of the ISP, which advertises a wrong DNS resolver? Or is the Atlas probe unable to query link-local addresses for DNS resolution? Even if it is so, is it a good idea for the Atlas Web site to display "undefined" where the raw results show that other resolvers worked?