title: [System.Net.Dns]::GetHostEntry method resolves IP to HOSTNAME without PTR record?
body: <p>I am trying to use <a href="http://msdn.microsoft.com/en-us/library/ms143998.aspx" rel="nofollow"><code>Dns.GetHostEntry</code></a> method to get the HOSTNAME for a given IP from the DNS server.</p>
  
  <p>According to the <a href="http://msdn.microsoft.com/en-us/library/ms143998.aspx" rel="nofollow">documentation</a>, the method first tries to do a reverse lookup on the IP address. In my case this is always successful when I use <code>Dns.GetHostEntry</code>.</p>
  
  <p>Now, the strange thing is that for the same IP nslookup doesn't give me anything. It either times out or gives me error: <code>UnKnown can't find 10.4.202.16: Non-existent domain</code>. When I look into the DNS server (2008 R2), I can not find any PTR records in de reverse lookup zone. So the fact that nslookup fails doesn't surprise me much.</p>
  
  <p>But what is going on here? Is <code>Dns.GetHostEntry</code> using some undocumented ways to obtain the HOSTNAME?</p>