Setting up S2S VPN. On both sites I have a DSL modem connected to a Router
doing NAT to the private interface of my BM38 server (router has a WAN
address assigned by ISP and a LAN address assigned by me).

When entering server addresses in iManager VPN Server Configuration which
address do I use: The static IP (WAN) our ISP assigned to the public side
of our router, the LAN address of our router (192.168.x.a) or the LAN
address of the Public Binding of our BM server (192.168.x.b).