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APM uses the WMI protocol by default to remotely connect to your Windows Server and request information from the WMI database. This approach avoids the need to install an agent on the remote Windows server to monitor service availability. This is known as an agentless monitoring technique.
On Windows servers where the firewall is turned on, it may happen that the WMI protocol is blocked, causing the monitored Windows services to return an Unknown state.
To avoid this situation, it is recommended that if you have a firewall running on your Windows servers that you verify that the following elements are respected. It is possible to use a GPO to push these firewall rules.
| Active | True |
| Program | All |
| Action | Authorize |
| Security | Required Auth |
| Protocol | 6 |
| Local Port | 135, 139, 445, 49154 |
| Remote Port | All |
| ICMP Parameters | All |
