using System;
   using System.Net;
   using System.Collections;

   ...

   // den Host Namen holen
   string hostname = Dns.GetHostName();

   IPHostEntry hostent = Dns.GetHostByName(hostname);   // Host Info
   Array ipArray       = hostent.AddressList;           // alle IP Adressen
   IEnumerator it      = ipArray.GetEnumerator();       // Iterator

   Console.WriteLine("Vorhandene IP Adresse(n) für " + hostname);

   while(it.MoveNext())
   {
      IPAddress ip = (IPAddress)it.Current;
      Console.WriteLine("Address: {0}", ip);
   }

   ...