<tr> <td>'''Always back-up the default iptables settings'''</td><td>When you install iptables in CentOS it already has some rules predefined.<br />Make a copy of the file that creates these rules (including the ones that allow communication with your other machines). This way you can always restore them to have a functional machine even if you completely mess up your rules.</td></tr>

<tr> <td>'''Don't Panic if disconnected from a VM'''</td><td> Some of the traffic between your host and VirtManager goes through IPtables.<br> When you mess with IPtables rules on the host, you might end up losing the console connection to the virtual machines.<br>'''Don't worry, the virtual machines are still running and you can still use them once you re-establish your connection'''.</td></tr>