Two IP address and AS2 URL

Hi

I am involved in a B2B conection using AS2 adapter. We are using B2B add on. Our PO server has an IP address which we use to connect using VPN. The client asks for the PO srver IP to be made public and we did that. Now the client wants our AS2 url.

I realize that it's http://ipaddress:port/AS2

Here which IP address we need to use? The public IP or the other IP?

Where do we get the alias name for the certificate used ?