What is the proper way to delegate to a private / hidden sub-domain?

[John Levine]

In article <mailman.359.1588795849.942.bind-users at lists.isc.org> you write:
>> I think one possibility (to avoid anycast) is to have an internal and
>> external view for the "example.net" zone, so it can delegate the lab
>> zones to different servers internally and externally.
>
>But how do you do that if the internal and external views are on 
>different servers with completely different IPs?

Don't Do That.

>I ask because now you're back to the same issue, just at the parent 
>domain:  How does the net zone delegate to different example zones 
>depending on if the client is internal or external.
>
>I don't see any options that avoid anycast.

This really seems like ordinary split horizon DNS.

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