Hi, all:<br><br>       I'm interested in issues on open DNS resolvers. In the following page, <br>          <span class="Object" id="OBJ_PREFIX_DWT63_com_zimbra_url"><a href="http://dns.measurement-factory.com/surveys/openresolvers.html" target="_blank">http://dns.measurement-factory.com/surveys/openresolvers.html</a></span><br>
<br>      It discusses how to probe open resolvers, but I have some questions<br><br>      1
 about the testing methodology, it needs to build a DNS server and check
 whether it receives queries. Why can we just use "dig @target_ip <span class="Object" id="OBJ_PREFIX_DWT64_com_zimbra_url"><a target="_blank" href="http://www.example.com">www.example.com</a></span>" and see whether we can get a result?<br>
<br>      2 for testing whether a ip is open resolver, the page recommends to use the following command line:<br>                               dig +short <a href="http://2.2.2.4.dnsbl.openresolvers.org">2.2.2.4.dnsbl.openresolvers.org</a>  <br>
         <br>         I test many IPs from the link: <span class="Object" id="OBJ_PREFIX_DWT65_com_zimbra_url"><a href="http://www.petercooper.co.uk/list-of-public-dns-servers-you-can-use-40.html" target="_blank">http://www.petercooper.co.uk/list-of-public-dns-servers-you-can-use-40.html</a></span> , and I got null results, which means<br>
 they are not open resolvers or they havn't been probed.  for example, I tested 67.138.54.100 and got null result<br><br>                                             [usr@canard usr]$ dig +short <a href="http://67.138.54.100.dnsbl.openresolvers.org">67.138.54.100.dnsbl.openresolvers.org</a><br>
                                             [usr@canard usr]$ <br>  <br>          But since I tested many ips and only got null results. Is my testing wrong or not?<br><br>     3 I tried <br>                           dig @<a href="http://2.2.2.4">2.2.2.4</a> <span class="Object" id="OBJ_PREFIX_DWT66_com_zimbra_url"><a target="_blank" href="http://www.google.com">www.google.com</a></span><br>
        
and got no good results, but in the page, 2.2.2.4 is an open resolver<br><br>     4 is there anybody who has a open resolver list?  if so, can you send me a copy? I need them to do some tests, thanks!