SBC sits on the internal network. This install is as easy as pie for SIP IMHO. The SBC has a connect of it's own to their router. The SBC will have an internal static IP address that is assigned by the IT guy or whomever. This is the address that's important to you. I've installed like 6 of these and they are like the easiest of all because you don;t have to deal with people not knowing how to configure their damn firewalls.