There is no option on the RRAS snapin to Allow Calling Computer to Specify its own IP Address, when the RRAS server is a member of a domain.
To work around this issue:
1. Set the remote access policy to Server settings define policy.
2. Use Regedt32 to navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RemoteAccess\Parameters\Ip
3. On the Edit menu, Add Value name AllowClientIpAddresses, as a type REG_DWORD. Set the data value to 1.
If the RRAS server is NOT a domain member:
1. Right-click My Network Places and select Properties.
2. Right-click Incoming Connections, select Properties / Networking.
3. Press Internet Protocol(TCP/IP) / Properties / Allow calling computer to specify its own IP address.
4. Close My Network Places.