Split pocket DNS question

[natrbrazell at cox.net]

I have  a potentially stupid question but here goes anyway.  I configured my DNS servers in a splitpocket configuration in my DMZ.  I have 2 zones internal and external but I only have 1 interface on the DNS servers.  My firewall has a global set of external IP's that will get forwarded to the DNS servers.  My question is with respect to zone transfers.  With one interface on the box when I restart my DNS services the private IP space gets sent to my slave DNS server as my public addresses so dnsstuff will say my DNS servers are being advertised as 172.16.x.x addresses which obviously causes problems.  Now the stupid question...

Am I supposed to have 2 interfaces in my Split DNS machines ?