Get the IP address of a machine connected to/in a VPN network

Question

I need to know the IP address of a machine connected to a VPN. I have used the following algorithm to do so:

if (NetworkInterface.GetIsNetworkAvailable()) { // First check if any connections are present
NetworkInterface[] interfaces = NetworkInterface.GetAllNetworkInterfaces();
bool vpnExists=false;
string ipAddr="?";
foreach (NetworkInterface Interface in interfaces)
{ // Loop through all interfaces present
    if (Interface.OperationalStatus == OperationalStatus.Up)
    { // consider only if an interface is currently active
        if (Interface.NetworkInterfaceType == NetworkInterfaceType.Tunnel) // refering to vpn
        { // vpn found              
            vpnExists=true;
            foreach (UnicastIPAddressInformation ip in Interface.GetIPProperties().UnicastAddresses) { 
                // Program control reaches here without any problem
                if (ip.Address.AddressFamily==AddressFamily.InterNetwork) { // this block does not execute as expected
                    ipAddr=ip.Address.ToString();
                }
            }
        }
        else
        { // vpn not found
            continue; // Goto another interface
        }
    }
  }             
}
/*
Final state of variables:
   vpnExists: true
   ipAddr: "?"
*/

The code functions perfectly till the VPN checking part (for all networks I've tried on) but does not display the IP address after the detection of VPN. I don't understand why the statement (ip.Address.AddressFamily==AddressFamily.InterNetwork) returns false as I believe that it is the correct way to get IP addresses.

Can anyone please point out why is this happening? And an in-depth explanation would also be helpful.

Thanks in advance.

UPDATE: This issue has been solved by mapping the IP address manually. Anyways, thanks to everyone who took interest and helped to solve.

Answer 1

If your network also supports IPv6 you should check for both ie instead of

if (ip.Address.AddressFamily == AddressFamily.InterNetwork)

use:

if (ip.Address.AddressFamily == AddressFamily.InterNetwork
 || ip.Address.AddressFamily == AddressFamily.InterNetworkV6)

You can see all the values of the AddressFamily enum here on MSDN.