Ah VPC. Are you sure your host machine is not a mac? I thought VPC was only for macs. If you were using a Mac, I'd recommend Parallels instead of VPC.

On both host machine & VPC the test page for port 6346 are both failing for you? This does suggest the router is at fault.

1. If you port forward, there's a few steps, the first is the most important; setting up a static ip address: How to set up a static IP address on XP which 'probably' needs to be done 'from' your VPC so the network ip address is correct.

2. Find your model on far right of this page: http://portforward.com/routers.htm under Westell. There are a few variations of the 327W model. Then click the ignore advert link at top right, find LW on following list. As for port to use, your choice. As suggested 6346 or even any port between 49152 - 65535. Use same port for both listening & connection. Port forward both TCP & UDP. That will mean the port forwarding will only apply to the VPC. The VPC being considered as a separate computer on the network. Port forwarding only applies to a single computer on any network because PF is based on ip address.
One thing I found different about using VPC was the network address was different to the one the main computer gave. Whereas Parallels shows the correct one. Hope that's not the scenario here. After port forwarding process is complete, not sure about Westell, but some brands/models you need to reboot the router or computer or both to get the process properly saved and started.