Secondary for a server with views

[Bowie Bailey]

I am attempting to use views to combine two of my DNS servers.  Setting
up the views is easy enough, but I'm confused about how to configure the
master/slave relationships.

The main server will have an external view and an internal view.  The
secondary server will need to mirror both of those views.

How can I have the secondary server mirror the external view?  If I tell
it that a zone is a slave, how can it query the master for the external
view of the zone rather than the internal view?  The documentation
mentioned using "keys" for this, but I could not find any examples.

-- 
Bowie