Networks

I have SBS2003 DC with DNS running and fwd goes to ISP. All is well there.

I have a secondary BDC 2003, it connects to PDC and I am able to replicate AD and all is well.

I bring up DNS service and when I try to add a zone as secondary, enter a new name dc2.ourdomain.local, then asks for IP of server to get it's data. I enter the PDC's IP.
This is when it displays Zone can not be created IP is invalid!!!
I am also able to connect to primary by typing its name say pdc1. Without creating a zone, but that defeats the idea of having a backup dns.
But can not add a secondary zone.

Any Ideas???

Thanks RG7