# Monitoring CPU, Memory, Disk Using SNMP

OpManager helps you monitor the performance metrics of any device that supports SNMP. The monitors for CPU, Memory, and Disk Utilization are automatically associated for the SNMP devices based on the [device template](https://www.manageengine.com/network-monitoring/help/device-templates.html) definitions.

For example, consider you've associated SNMP-based monitors to the default template for a server type (say Linux) in OpManager. So from then on, all Linux servers discovered into OpManager will have those SNMP-based resource monitors associated by default. This doesn't apply only for just one device category, but these definitions can be used to associate related monitors to any SNMP-enabled device.

If you do not see these monitors associated to the devices, it could be due to any or all of the following reasons:

- **Monitor absence:** These monitors may not be present in the device template.
- **SNMP Disabled:** SNMP may not be enabled on the device. In such case, enable SNMP and add the monitors to the device once again.
- **Incorrect Credentials:** Incorrect SNMP credentials might be associated. Check the credential details like the SNMP version, community string etc.

## Steps to add the monitors to the device once again

Monitors can be re-associated to the devices in the following ways.

- [From Performance monitor settings page](https://www.manageengine.com/network-monitoring/help/host-resource-monitoring.html#performance_settings)
- [From Device Snapshot page](https://www.manageengine.com/network-monitoring/help/host-resource-monitoring.html#snapshot_page)
- [From Device Templates](https://www.manageengine.com/network-monitoring/help/host-resource-monitoring.html#device_templates)
  - [To check if the SNMP agent in the device returns response](https://www.manageengine.com/network-monitoring/help/host-resource-monitoring.html#check_snmp_response)

### 1. From Performance monitor settings page

- Navigate to **Settings -> Monitoring -> Performance Monitors**.
- You can find all the [SNMP monitors](https://www.manageengine.com/network-monitoring/help/performance-monitors-list.html) listed down.
- To associate a monitor to device(s), go to the respective monitor and click on the associate button that is found under the **actions column**. You can also click on the "**Associate**" option on the top right corner and then select the monitors and devices in subsequent steps to associate monitors with devices.
- Now, select the devices from the "**Available Devices**" column and then move them to the "**Selected Devices**" column.
- Click on "**Apply**" or "**Apply & Overwrite**" based on your preference. The monitor will now be successfully associated with the respective device(s).

![Host resource monitoring using snmp in OpManager: Associating monitors from performance monitor settings page](https://www.manageengine.com/network-monitoring/help/images/snmp-1.png)

To know more about associating monitors with devices, refer [here](https://manageengine.com/network-monitoring/howto.html#monitor-association-based-on-filters).

**NOTE**: Devices will be associated with the monitors only when the respective credentials are enabled in the device.

### 2. From Device Snapshot page

- Navigate to **Inventory -> Devices** and then click on a device to open its [Snapshot page](https://www.manageengine.com/network-monitoring/kb/device-summary-device-snapshot.html).
- Open the **Monitors** tab. Under the **Performance monitors** section, click on the "**Actions**" button at the top right corner of the page.
- Now, select the SNMP monitors for Disk, CPU and memory from the list of monitors displayed under the HOST-RESOURCES category.
- Click on "**Add**" to apply the changes.

![Associating monitors from the device snapshot page](https://www.manageengine.com/network-monitoring/help/images/snmp-2.png)

### 3. From Device Templates

- Navigate to **Settings -> Configuration -> Device Template**.
- Open a template and click on the "**Add**" button that is found at the right of the "**Associated Monitors**" section.
- Now, select the monitors you want to add and then click on "**Save**" or "**Save & Associate**" based on your preference. The monitors will now be associated with the [device template](https://www.manageengine.com/network-monitoring/help/device-templates.html). Any new device about to be associated with the template in the future, will automatically be associated with these monitors.

[Click here](https://www.manageengine.com/network-monitoring/help/getting-started-monitoring.html) to know more about adding monitors.

![Host resource monitoring using snmp in OpManager: Associating monitors from the device templates](https://www.manageengine.com/network-monitoring/help/images/snmp-3.png)

## To check if the SNMP agent in the device returns response, try the following:

- Click the **Test Monitor** icon against any of the associated monitor names. It does a dynamic query to the device for the value of the selected resource, and show the data.
- Incase the agent does not respond, you see a message to this effect.
- Refer to the [troubleshooting tips](https://www.manageengine.com/network-monitoring/troubleshooting-guide.html#monitor) to resolve the issue.

It is recommended to use [WMI](https://www.manageengine.com/network-monitoring/help/wmi-monitoring.html) or [CLI](https://www.manageengine.com/network-monitoring/help/cli-monitoring.html) to monitor Windows or Linux devices respectively. But if both these protocols aren't available or if you want to monitor additional metrics using SNMP, you can also do that in OpManager.