What happens if the NS records in a zone don't agree with the root nameserver delegation for that same zone? In other words, if a registrar knows that the authoritative nameservers for example.com are server-1 and server-2, and this information is populated to the root nameservers.
But server-1 and server-2 contain zonefiles which list a different pair of servers (server-a.example.com and server-b.example.com) as the NS records, along with the appropriate A records, should this work?
As I understand it this is not a valid configuration, but I have seen it work, and don't understand why resolvers are following the NS records, instead of the root nameserver delegation.
Which zonefile is actually in use, is it the zonefile on server-a/b or server-1/2?