title: tcpdump returns 0 packets captured, received and dropped
body: <p>I am currently trying to debug a networking problem that has been plaguing me for almost three weeks. I'm working with openstack and can create virtual machines and networks fine but cannot connect to them at all. When I run this command from the server, i have to ctrl+c to stop the time-out and it returns:</p>
  
  <pre><code>[root@xxxxxx ~(keystone_admin)]# tcpdump -i any -n -v 'icmp[icmptype] = icmp-echoreply or icmp[icmptype] = icmp-echo'
  tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
  ^C
  0 packets captured
  0 packets received by filter
  0 packets dropped by kernel
  </code></pre>
  
  <p>I'm not sure if this is exclusively and OpenStack problem or just a networking problem in general, but i know that 'tcpdump' is supposed to return something other than 0 packets captured, received or dumped. I am new to networking and therefore do not have much experience so please be gentle. Any help is appreciated. Thanks.</p>