Connecting all the pieces together was much easier than I expected it to be. There are only three pieces (XP Client, IPS, ACS) external to Dynamips, all running VMware that need to be part of the Dynamips lab network.
If you are using Windows, like I am, you need to create a few Loopback adapters on Windows. http://support.microsoft.com/kb/839013 explains how you can do that. Once you have the loopback adapter, and have assigned an IP to it, you need to bridge your VMware adapters to them. To do that, open up the VMware Server Console. Click on Host -> Virtual Network Settings, select the Host Virtual Network Mapping, and then pick the VMnet adapter that you want to bridge to the Loopback adapter you created. All the adapters appear in the drop-down.
Now, on GNS, create a cloud, right-click on it and select Configure. Select the loopback adapter from the drop-down list, and click Add. This is your link into the Dynamips network. That’s it folks! Now your VMware machine should be able to talk to your Dynamips network. Zoom zoom!