A: You will need to give the master and slave multiple IP addresses and
use those to make sure you reach the correct view on the other machine.

e.g.
Master: 10.0.1.1 (internal), 10.0.1.2 (external, IP alias)
    internal:
match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
notify-source 10.0.1.1;
transfer-source 10.0.1.1;
query-source address 10.0.1.1;
    external:
match-clients { any; };
recursion no; // don't offer recursion to the world
notify-source 10.0.1.2;
transfer-source 10.0.1.2;
query-source address 10.0.1.2;

Slave: 10.0.1.3 (internal), 10.0.1.4 (external, IP alias)
    internal:
match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
notify-source 10.0.1.3;
transfer-source 10.0.1.3;
query-source address 10.0.1.3;
    external:
match-clients { any; };
recursion no; // don't offer recursion to the world
notify-source 10.0.1.4;
transfer-source 10.0.1.4;
query-source address 10.0.1.4;

You put the external address on the alias so that all the other
dns clients on these boxes see the internal view by default.

A: (BIND 9.3 and later) Use TSIG to select the appropriate view.

Master 10.0.1.1:
key "external" {
algorithm hmac-md5;
secret "xxxxxxxx";
};
view "internal" {
match-clients { !key external; 10.0.1/24; };
...
};
view "external" {
match-clients { key external; any; };
server 10.0.0.2 { keys external; };
recursion no;
...
};

Slave 10.0.1.2:
key "external" {
algorithm hmac-md5;
secret "xxxxxxxx";
};
view "internal" {
match-clients { !key external; 10.0.1/24; };
};
view "external" {
match-clients { key external; any; };
server 10.0.0.1 { keys external; };
recursion no;
...
};