Drop a label in your aspx page.
in code behind:
1: string strHostName = System.Net.Dns.GetHostName();
2: IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
3: IPAddress ipAddress = ipHostInfo.AddressList[0];
4: label1.Text = Convert.toString(ipAddress);
If you have any question, shoot me an email