im interested in hearing someone who does.
this is a kind of interesting subject...
i visited a couple of websites maybe they can be some help more then I
 
 
www.firstvpn.com
http://www.isp-planet.com/technology/vpn-customers-a.html
http://www.perle.com/products/prod-family/routers
 
you can download and read what they have to say about it, it may help here...
http://www.firstvpn.com/research/papers1.html
good luck

Thanks for the links, I'll do it myself it doesn't look like there are many with the experience.

VPN is a bit of an overkill. Most efficient way to do it is (if you are using IIS) if you add the IP of the other sites to the trusted IP's list on your site settings.
 
Theoretically it is ossible to use VPN but i frankly do not see much point. if you can maybe explain your application requirements i might be able to help you better.

IIS? How is IIS going to help me with the VPN solution? Yes, you can use IIS in an "Extranet" and block/grant IP's/ sites but here we are talking about routing & internal network WAN no websites.
 
I have decided to use SonicWall and it's excellent reasonable priced and very secure easy maintance and etc. It's pretty cool

Well with IIS on top of granting blocking IP's you can also define subwebs on anywhere.
when you are using home directory setting, you can point it to another location on your Lan or wan it might even be an off-site location.
It does not care.
 
I did not know what you were looking for exactly, I use this to keep DB's on another physical box.
 
So customers can not just nick them and use them without my license and contract.
 
PS. Data belongs to them DB code to me. It is not illegal.