Do I need to implement anything special to enable VPN access within my iPhone app? I have an iPhone application that I would like to use to access a VPN.  I've configured the VPN through the Settings app on the iPhone, but my app still can't access the VPN to get data.   A similar Mac application I developed worked without issues through this VPN.

The connection for VPN used is "PPTP".  In Safari on the devices, typing the url as http://vpnip shows a page with IIS.

Is there anything I have to programmatically enable or configure inside the app to look for the virtual private network?
Most likely, it has to do with name resolution. Try providing a URL with a fully qualified domain name to your server - http://vpnip.mydomain.com or something. Something that is resolvable via the DNS. If no such name exists, try that server's IP address (as the first troubleshooting step).