You must not understand NAT then. If you want your VM machine to use a loopback IP address then I'd suggest using the host-only or bridge adapter - not NAT. Host-only or bridge will allow you to set the IP address to loopback, or any other IP address in the VM machine. Also from my experience with VM Workstation and Fusion you don't set the IP address in the settings of VMWare, rather they are set in the VM machine OS, just like you'd do on any other native operating system. The VMWare Fusion gets the IP from the vmnet processes, whether it be NAT, Host-Only, or Bridge. NAT is assigned by the vmnet8 process. vmnet1 and vmnet0 will be determined by the VM machine OS, and that could be a static IP or DHCP - up to you. Host only however is a bit different, but does allow you to configure a virtual VLAN. Vmnet processes are simply "virtual" network interfaces sharing your physical network interface.
Sorry - i had not made myself clear before. I have either bound the vmware networking to a loopback adapter, set with a static ip, so that in windows, ANY OS running gets a valid IP and not the windows autoconfig address so that the various environments ( all servers or virtual appliances) can have a fixed ip.
OR, i set the VMnet ethernet adapter to a specific range/subnet, and give my environments ip's in that valid range. 192.168.223.x at the moment- i have about 10 Linux VM appliances ( several of which need to run at once) in that range.
So, in trying to use my existing VM's , which currently expect to use a static IP, i would like to find out what IP Vm fusion is providing when i have NAT switched on- i could them access the vm's via a browser and change the networking settings- ironically i can use DHCP inside some of them, if only i could access them via a browser first. Bridging is not an option as it will not work with some of the virtual appliances i use. The VM's must be accessible from browser on my MAC,talk to each other, and must also be able to get to the internet directly.
The other thing i am not certain about is if the inbuilt firewall is stopping the communication. Would it pop up if there was something wrong?
Thanks for the comments.