Unable to obtain IP address if IPv6 is turned on

 
 
Hello,
I am trying to collect the client IP address by using below command in ASP.NET.  Within VS2012, ClientIPAddress returns "::1".  I noticed the client computer has both IPv4 and IPv6 IP address turned on.  How can we prevent this from happening in production where some computer has IPv6 turned on some don't. 
string clientIPAddress = Request.ServerVariables["REMOTE_ADDR"];              
 
Thanks,
Brian