title: dig returns SERVFAIL but +trace works
body: <p>Here is the main problem:</p>
  <pre><code>dig maktabkhooneh.info +trace
  </code></pre>
  <p>works perfectly fine and returns the right answer.</p>
  <pre><code>dig maktabkhooneh.info
  </code></pre>
  <p>(without +trace) returns:</p>
  <pre><code>; &lt;&lt;&gt;&gt; DiG 9.8.1-P1 &lt;&lt;&gt;&gt; maktabkhooneh.info
  
  ;; global options: +cmd
  
  ;; Got answer:
  
  ;; -&gt;&gt;HEADER&lt;&lt;- opcode: QUERY, status: SERVFAIL, id: 58716
  
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
  </code></pre>
  <p>What could be the reason? I was reading <a href="https://serverfault.com/questions/65499/dig-trace-resolves-while-without-doesnt">this</a>. Is it the only possible reason that I changed domain data 12hrs ago? Isn't there any other possible reason for <code>SERVFAIL</code>?</p>
  <p><strong>extra info:</strong></p>
  <p>I have two BIND servers working on 168.144.251.73 (master) and 168.144.92.50 (slave).</p>
  <p>and on the master I have:</p>
  <pre><code>$TTL 300
  
  maktabkhooneh.info.        IN    SOA     ns1.maktabkhooneh.info.   
  admin.maktabkhooneh.info. (
  
  2012060201    ; Serial
  
  86400    ; Refresh
  
  7200     ; Retry
  
  3600000    ; Expire
  
  300 )  ; Minimum
  
  
  maktabkhooneh.info.        IN    A       168.144.97.83
  
  maktabkhooneh.info.        IN    NS      ns1.maktabkhooneh.info.
  
  maktabkhooneh.info.        IN        NS      ns2.maktabkhooneh.info.
  
  ns1     IN    A   168.144.251.73
  
  ns2     IN    A   168.144.92.50
  
  www     IN    CNAME   maktabkhooneh.info.
  </code></pre>