That's not really how customer DNS works, so you're talking about a custom monitoring project. It doesn't seem very hard to monitor the consensus - get a stream of domains and run "dig" against the known endpoints.
But if you want an actual server doing that, I don't think there's much point. You'll get differences for various valid reasons. Entries changing, different anycasts getting different geo responses, etc. It's a bit like "a man with a watch knows the right time, a man with two watches can never be sure".
So the answer is really - why do you want to do this? Different reasons here lead to different approaches.
But if you want an actual server doing that, I don't think there's much point. You'll get differences for various valid reasons. Entries changing, different anycasts getting different geo responses, etc. It's a bit like "a man with a watch knows the right time, a man with two watches can never be sure".
So the answer is really - why do you want to do this? Different reasons here lead to different approaches.