title: Zabbix agent on is unreachable for 5 minutes
body: <p>I used zabbix 2.4 and it worked perfectly. I decided to upgrade server and all agents to 3.0 LTS. I did not change any settings in agents and server conf-files and did not change any settings wia web.</p>
  
  <p>But now I receive messages</p>
  
  <blockquote>
    <p>Zabbix agent %servername% on is unreachable for 5 minutes</p>
  </blockquote>
  
  <p>This agent works on the same machine with zabbix-server. More strange that I receive other messages from this agent. So I can see that agent works and server can communicate with it.</p>
  
  <p>After I started to receive this error message I tried to change IP of agent. First it was 127.0.0.1, after I changed address to network's IP: 192.168.x.x. Nothing changed. I receive unreachable message every 6-7 minutes with the other messages from this agent. And also this agent is green via web-interface. </p>
  
  <pre><code>zabbix_get -s 127.0.0.1 -k agent.ping
  </code></pre>
  
  <p>also returns <code>1</code>.</p>
  
  <p>How to fix problem?</p>