SNMP Graph Item Properties

Use the Graph Item Properties dialog box to add an SNMP item to the graph or change an item's properties.

1. In the Host box, enter the hostname or IP address of the device for which you want to graph SNMP objects, or select one from the list box.
2. If necessary, change the string in the Community Name box. The default string is public.

   The default (public) will work for most SNMP devices unless the administrator has specifically removed public and replaced it with a string of their own. If you know a device is manageable via SNMP and public doesn't work, you will have to talk to the owner of that device to get a community name that will work.

3. Use the Item and Instance boxes along with the MIB tree to select the SNMP object that you want to graph.

   If you know the object identifier for the SNMP object, you can enter it in the Item box.

   To browse the available SNMP objects, click the browse button and use the MIB tree. Select an object in the MIB tree and click OK to enter its object identifier in the Item box.

   Use the Instance box to enter the instance of the selected SNMP object.

4. Set any of the following options to determine how to graph the values for the SNMP object:
   • Absolute values. When selected (or turned on), graphs the reported values of an SNMP object rather than graphing the change between the last reported value and the current value (which is the default method). When graphing a counter, such as ifOutOctets, the reported values will continuously increase, so if you select Absolute values, the graph will continue to "stair-step" up the scale. Counters are best graphed using the default method, which uses the change in value. Absolute values are appropriate for SNMP objects that have integer values, such as the number of FTP users on an FTP server.
   • AutoScale. When selected, the graph scale for the SNMP object is determined by the graphing utility. This is a relative scale that is calculated to make the graph fit into the vertical scale. If you turn off this option, the Scale option becomes active and you can enter a value to scale the graph.
   • Scale. When AutoScale is cleared (not checked), you can enter a fixed value in this text box to determine the scale of the graph. You may want to try different values in this box until you find a scale that is useful.
   • Bytes to Bits. When selected, multiplies the value reported for the SNMP object by 8 to approximate the count in bits, and then graphs the result. This option can be used with SNMP objects that are counters, for example if you want to know the baud rate while monitoring a T1 router port, you want (ifOutOctets * 8) to give you a value close to the real baud rate.
   • Rate per second. When selected, it calculates the average change per second in the values reported for the SNMP object, and then graphs the result. To calculate this average, it takes the difference between the latest reported value and the previously reported value, then divides by the number of seconds between reported values. This is useful when the graph Interval is different than one second. You cannot use this option with the Absolute values option.
   • Reset values. When selected, it clears the values for the selected SNMP object when you exit the dialog box. You can clear the values for all SNMP objects on the graph from the Edit menu by selecting Clear.
   • Line width. Sets the width of the line that represents the selected SNMP object on the graph. Select a width from the list box.
   • Color. Sets the color of the line that represents the selected SNMP object on the graph. Select a color from the list box.
5. Click OK to add the SNMP object to the graph.