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Graphing SNMP Values

Some of the SNMP objects are best monitored by displaying their changing values in a graph. WhatsUp Gold's SNMP Graphing Utility lets you select one or more SNMP objects and show a real-time graph of their values. You can also save a particular graph and later open the graph to resume graphing the SNMP objects.

The main window of the SNMP Graphing Utility shows a line graph for each SNMP object added to the graph.

Up to 20 SNMP objects can be active on the graph. You can set the color and line width to distinguish each graphed object.

By default, the SNMP Graphing Utility graphs the change between each reported value of the SNMP object. You can set the utility to graph only the reported values for an object. For more information, see "Adding, Editing, and Deleting SNMP Objects".

Starting the SNMP Graphing Utility

To start the SNMP Graphing Utility, do one of the following:

Adding, Editing, and Deleting SNMP Objects

To add an SNMP object to the graph:

  1. From the Edit menu, select Add Item->SNMP Item. The Graph Item Properties appear:
  2. In the Host box, enter the host name or IP address of the device for which you want to graph SNMP objects, or select one from the list box.
  3. If necessary, change the string in the Community Name box. The default string is "public." The default (public) will work for most SNMP hosts 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.
  4. Enter the Item and Instance numbers to specify the SNMP object that you want to graph. (Use the Browse button to the right of the Item box to view the MIB tree and select an object. When you select an object in the MIB tree, its object identifier is entered in the Item box.)

    For background information on item and instance numbers, see "SNMP Overview". To customize the MIB tree to include vendor-provided objects that are specific to your enterprise, see "Setting Up the MIB Identifiers".

  5. Set the item graphing options:

    Absolute values. When selected, graphs the reported values of an SNMP object rather than graphing the change between the last reported value and the current value (default method). You probably want to turn off Absolute values when graphing a counter, such as ifOutOctets; otherwise, the graphed values may be difficult to read.

    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.

    Bytes to bits. When selected, multiplies the value reported for the SNMP object by 8 to approximate the count in bits. 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.

    Reset values. When selected, 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 by selecting Clear from the Edit menu.

    Line width. Sets the width of the line that represents the selected SNMP object.

    Color. Sets the color of the line that represents the selected SNMP object.

    Scale. When AutoScale is turned off, 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.

    Rate per second. When selected, 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 option is useful when the graph Interval (in Graph Options) is different than one second. You cannot use this option with the Absolute values option.

  6. Click OK to add the SNMP object to the graph.

Viewing Item Values

You can view the raw data used to generate the graph for an SNMP item. Select the graph item in the Legend, then from the Edit menu, select View Item Values.

The "View Item Values" window shows the following data for the SNMP object:

Title bar. Shows the IP address of the selected host and the object identifier for the SNMP object.

Time. Time the value was reported.

Value. The absolute value reported by the SNMP object.

Diff. This is the difference between the reported value and the previously reported value. (Note that this value may not make sense if the graph is at a "wrap" point.)

Reported. This is the actual value used in the graph. This value depends on the setting in the graph item's properties, which can be set in one of the following dialog boxes: Graph Item Properties, Graph Accumulator Properties, Graph Timer Properties. If the item is set to report Absolute value, this value will be equal to the absolute value. If set to report Bytes to bits, this value will be the absolute value multiplied by 8. If set to report Rate per second, this value will be the difference between the last two reported absolute values divided by the time difference (Time Diff). If both Bytes to bits and Rate per second are selected, the reported value will be equal to the difference between the last two reported absolute values multiplied by 8, then divided by the time difference (Time Diff).

Time Diff. This is the difference (in milliseconds) between the time the last value was reported and the time the previous value was reported.

Click Refresh to update the displayed values.

Editing Item Properties

To edit a graph item's properties:

  1. To select the item to edit, do one of the following:
    • In the graph legend, double click the item you want to modify.
    • In the graph legend, click the item you want to modify, and then from the Edit menu, select Item Properties.
    • In the graph legend, right-click the item you want to modify, and from the right-mouse menu, select Properties.

      The following dialog box appears.

  2. Make any changes to the properties and click OK to save them and exit the dialog box.

Deleting Items from the Graph

You can delete an item from the graph at any time. In the graph legend, do one of the following:

  1. Click the item you want to delete, and then from the Edit menu, select Delete Item.
  2. Right-click the item you want to delete and then from the right mouse menu, select Delete.

Saving and Opening Graph Files

You can save a graph to a file and it will save the selected graph items and options. Data values are not saved. You can later reopen the graph file and resume real-time graphing of the saved SNMP items. WhatsUp Gold SNMP graph files use the extension .wgg.

To save a graph:

  1. From the File menu, select Save Graph. The "Save As" dialog box appears.
  2. In the File name box, enter a file name with a .wgg extension.
  3. Click Save to save the graph objects.

To open a saved graph:

  1. From the File menu, select Open Graph. The "Open" dialog box appears.
  2. Select a graph file name (with a .wgg extension) and click Open.

Editing Graph Properties

Use the "Graph Options" dialog box to set the layout of the graph window, the interval (or frequency) for recording values for the SNMP objects, and whether you want to record the data to a file.

To view the properties: from the Graph menu, select Properties.

Legend. When selected, the Legend appears at the bottom of the graph window. The Legend displays each graphed SNMP object and its associated device, as well as any accumulator items.

Interval (seconds). Sets the time interval at which the graph records values.

Vertical (y-axis). When Grid is selected, displays lines across the graph to help you read the vertical graph. When Labels is selected, values are displayed next to the y-axis. The Maximum determines the highest value on the y-axis scale, as well as the internal values. This value cannot exceed 1500.

Horizontal (x-axis). When Grid is selected, displays lines across the graph to help you read the x-axis values. When Labels is selected, values are displayed next to the x-axis. The Maximum determines the highest value on the x-axis, as well as the internal values. This value cannot exceed 1500.

Save Window Location. When selected, saves the position of the Graph Window so that it always opens in the same location on your screen.

Record data to. If you want to save graph data, select this box and enter a file name. The file is saved in the WhatsUp Gold directory. The file format is tab-delimited and can be imported to a spreadsheet application.

Append new data to datafile if it already exists. By default, this is selected. Whenever the graph is running, the SNMP values will be appended to the existing file. If this is NOT selected, the new data will replace the existing file.

File Format: 

Date [tab] time [tab] first item value [tab] second item value [tab] ...

For example, a graph with three items would show the date and time plus the three values recorded at that time. The heading shows the IP address and SNMP object identifier for each graph item. 

[156.21.50.12]:1.3.6.1.2.1.2.2.1.10.3 
[156.21.50.12]:1.3.6.1.2.1.2.2.1.10.4	[156.21.50.12]:1.3.6.1.2.1.2.2.1.16.3 
 
01/03/2002	  11:07:34	  1037	8267	1006689	 
01/03/2002	  11:07:35  	1695	8743	1031456	 
01/03/2002	  11:07:36	  2067	8156	873944

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