ok, so you will delegate your sub zone wip to two GTMs. when client will request for its resolution, the public server will advertise a cname to the wip subzone and both GTMs as NS for this subzone. don't remember if it's in the same responseor a second one but it doesn't mater. At one time you client (ldns) will receive both GTM IP as NS for the subzone and he will pick up one! which one is depending on the public DNS server advertising NS in different order and ability of your client to manager two NS for a zone.
But this should not be imporant, either one will be choosen by the client. Why it is not important : first GTM are synchronize in a GTM group, which means they have the same view of your network, they exchange states, persistence records, ie if you send a request at the same time on both they should give you same response. secondo, if you have latencies for example one GTM in the US another one in europe, the DNS querie is just a one time action, meaning you will suffer from RTT just for the resolution request.
Cirrostratus
