PRTG Manual: SNMP IF Utilization
The SNMP IF Utilization monitor allows you to monitor the utilization of a device interface using the SNMP protocol. When a IF utilization monitor runs it requests the devices interface utilization from the monitored devices and compares the result with the monitors specified thresholds.
The Interface monitor editor contains the following tabs that require configuration: Settings, Devices, Schedule, Event, and History.
The Schedule, Events and History settings are the same for all monitor types. See Configuring Monitors for more information about configuring these settings. For the other tabs see the information below.
Name
The Monitor name is the name of the monitor used to refer to the monitor in the monitors list view, and in monitor events and notifications. Monitor names must not be unique but it is recommended you use unique names to differentiate them.
Verify OperStatus = DOWN
The verify OperStatus down checkbox determines whether the monitor should test for the OperStatus to be up or down. If this option is not selected the monitor will fail if the OperStatus is down. If this option is selected the monitor will fail if the OperStatus is UP, this is used to monitor/ensure that a particular interface is down.
Use Usage Thresholds
The Use Usage Thresholds value specifies whether to compare the utilization response with the thresholds when determining the monitor state. If the utilization percentage exceeds the critical or warning percentages a down or warning state occurs respectively. The warning percentage must be less than or equal to the critical percentage.
The devices tab allows you to select which devices and its interfaces to monitor. The Interface monitor can monitor one or more interfaces on a device.
To add devices/interfaces to the monitor select the 
button in the lower left corner. A device selector will be presented allowing you to choose one or more devices to monitor. When the device is selected each of the devices up interfaces that are passing traffic will be added to the monitor. Note: Only devices with an assigned SNMP credential will be available in the picker. If you do not see a device ensure it has the appropriate credential assigned.
To edit which interfaces on a device to monitor. Select the device or one of its interfaces in the list and press the edit button 
. A list of all of the devices available interfaces will be presented. Check the interfaces you would like to monitor and close the dialog. The monitored interfaces list will be updated to reflect the changes. Note: If an interface is not available it could be because it was not discovered during device discovery. To update the list ensure valid credentials are available and rediscover the device. See Monitored Devices for more information.
To remove a device or interface from the monitor select the device or interface in the list and press the delete button 
. The device/interface will be removed from the monitor.
