vCloud Director external Network question

I am newbie here and would like to get some clarification on the external network for the vCloud Director.

when configure External Network, am I suppose to supply the public IP address that assign/allot to me by the ISP or the private IP address that I want to use for the vCloud as external network then mapped 1:1 public ip to this private external network?

so basically I am not sure what type of imformation that i need to enter here.

Network mask:

Default gateway:

Primary DNS:

Static IP Pool Range:

if private then, this ip pool define in the firewall apart from the internal network?

thanks all

J