vmware fusion: how is the gateway IP decided in NAT networking mode?

Question

I recently did a clean install from Mac OS X Snow Leopard to Mac OS X Lion.

I put all my Vmware Fusion guests in NAT mode with static IP'. All this time in Snow Leopard I had all my guest OS' referring to Mac OS X with a gateway IP: 172.16.224.4

A recent clean install to Lion also required a fresh install of Vmware Fusion. I brought back all my guest VMs without any change, but I could no longer ssh into them, because the gateway IP now had changed from 172.16.224.4 to 192.168.72.2. So I had manually change gateway IPs in all my guest VMs

It makes me wonder where are these settings stored which decides what would be the gateway IP of the host in NAT networking mode for Vmware Fusion?

Answer 1

There's a whitepaper on how to do change these settings. In general, I look for things like this in the Fusion Power User's Guide

So that this answer isn't just a set of links, I'll provide some actual information. Fusion stores these settings in /Library/Preferences/VMware Fusion/networking. It is possible to change that file manually, reboot, and get the new settings, but that isn't recommended. There are configuration scripts to help you set things up the way you want. The reason the IP addresses changed is that on install, Fusion needs to establish two network interfaces, a host-only interface (typically called vmnet1) and a NAT interface (typically called vmnet8). Both of the interfaces get their own IP's (these IPs become the default gateway for your VMs) and DHCP configured to hand out addresses for you VMs. Fusion chooses these two IP ranges in a way that attempts to ensure they aren't already in use on your host as that would problems. On a fresh install of Fusion, it isn't uncommon for the auto-picked ranges for vmnet1 and vmnet8 to change.