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A Tutorial about mc2

This file is a brief tutorial about mc2. It describes the basic tasks that can be performed with mc2.

Overview

The mc2 Window

Get a Cfg

The Edit Target Window

Import a Target

Copy a Target

Delete a Target

Check a Target's Port

Save a Cfg

Summary

 

Overview MC2, the MRTG Configuration Checker, lets you edit mrtg 2.x configuration files, in this manual refered to as "Cfg files". It allows the creation of new files using data polled from different network devices as well as altering target data.
MC2 consists of a Java Applet (Graphical User Interface, functions to edit the Cfg files) and some CGI scripts written in perl.
While sitting at his desktop machine, the user can remote configure the CFG files which are actually stored on a server (UNIX box) on which mrtg runs.
To use MC2 you'll need a Java 1.1 capable web browser such as Netscape Navigator 4.0.5. By pointing your web browser to the HTML page of MC2, your browser should automatically load Java and the applet (if your security options allow this). It will automatically bring up a window, the MC2 window.

 

The mc2 Window The mc2 Window is the main window of the tool. It lets you manage the CFG structure (that is the content of the Cfg File you are working on), open and save Cfg files as well as edit them.
The most important part of the window is the list. If a Cfg is active, its targets (interfaces to be controlled, one target per interface) are displayed in the list. Each line stands for a target, and it displays the Target Name, the Address (hostname or IP address of the target device), the interface description, the IP number of the interface and the SNMP Port number of the interface.
Above the list are some textfields with values which are "global" for all targets in the Cfg file. Enter or edit data in this field when a Cfg is active ( = is loaded).
At the right hand of the list are some buttons which provide the basic functions of MC2:
  • Get Cfg Button: Opens a Cfg file or polls data from a device
  • Save Cfg Button: Saves the Cfg to a file on the server (= the machine on which mrtg runs)
  • Edit Target Button: Edit the selected target
  • Import Target Button: Add some Targets from a Cfg file or network device to the actual Cfg
  • Copy Target Button: Makes a copy of the actual target
  • Delete Target Button: Deletes the selected target from the Cfg.
  • Check Port Button: Use this button to check if the port number of the interface is correct

 

Get a Cfg Click on the Get Cfg Button to get a Cfg. An Open Dialog appears. You can either choose an existing Cfg file from the server or a network device. The dialog shows all directories and files in the current directory of the server's file system. Normally, this is the directory in which the mrtg config files are located.
To choose an existing Cfg file, navigate thrue the directories: To open a directory, double click its name or select it and press Open. To get one directory up, simply double click the two dots ("..") in the first line of the list. If an error message saying similar to "I/O error: Document contains no data" appears, then you may not have the necessary access rights.
When you've reached the directory in which the desired file is, either double click the file or select it with one click and press the Open button.
If you want to make a new Cfg file, you can poll data from a network device. In this case, enter the SNMP Community ("public" in most cases) and the hostname (or IP) of the device in the format public@hostname. Then press the Open Button.
If everything was correct, the tool will now load the Cfg data and present it in the list of the MC2 Window.

 

The Edit Target Window A double click on a target in the list or a click on the Edit Target button will open the Edit Target Window. Basically, it contains a text field for every entry in a target. You can edit those entries by clicking into the field an edit the text.
Move the mouse over the textfield to get some information about the entries.
There's a Reset Button who will cause all entries of the target to reset to their values before the Edit Target Window was opened. All changes made to this target will be lost.
The Left ("<-") and Right ("->") Buttons let you scroll one target "up" and "down".
The OK Button will close the window and return you to the MC2 Window.
The Cancel Button closes the window as well, but it discards your changes (if you confirmed it in the warn dialog).

Import a Target The click on the Import Target Button opens an Open dialog, which -- in contrary to get a Cfg -- doesn't replace the actual Cfg by the new targets, but adds the new targets on top of the actual Cfg. Use this function to compose a Cfg file which has targets from different network devices.

 

Copy a Target The Copy Target Button does what its name says, it makes an identical copy (a "clone") of the selected target.

 

Delete a Target Deletes the selected target after the user confirmed it in a dialog.

 

Check a Target's Port Number After a router reconfiguration or a change in the network structure the SNMP Port number of the interface may be wrong. This will cause problems because mrtg identifies an interface not by its interface name, but by its SNMP Port number.
If mrtg is using the wrong (old) SNMP number, it (and you) will get confused which interface is which.
So it's important to make sure that it always uses the correct Port number.
You do so by clicking on the Check Port Button. It opens a dialog at which you specify the SNMP Community and the hostname of the device which's Port number has to be checked.
After a few seconds (polling the data may take some time, maybe even minutes), in the Check Port Window are all interfaces of this device listed. You can now check the port number using the interface's name and IP. If you discover a different Port number, do the following:
  1. Select the target with the wrong Port number in the list of MC2.
  2. Select the corresponding interface with the correct Port number in the CheckPort Window.
  3. Click on the Update Port Button in the CheckPort Window.

When you've finished, close the CheckPort window by clicking its Close Button.

 

Save a Cfg A click on the Save Button will bring up a Save Dialog. Maneuvering works the same way as in the Open Dialg. Enter an accurate file name an press the Save Button to save the file. If a file with the same name exists already in the same directory, it will be saved to a backup location and then be overwritten.
If a dialog similar to "There was an error while saving" appears, check if you have write permission of that directory.

 

Summary Create a new Target
  1. Open an existing file or choose a network device by its hostname.
  2. Remove all interfaces you don't want to monitor.
  3. Add additional interfaces from other devices using the "Add Target.." button if you wish to.
  4. Edit the targets.
  5. Save the targets to a file.
  6. Run mrtg manually at least 3 times until all error messages are gone.
  7. Edit your crontab entries with your favorite editor.
  8. Enjoy your new graphs.

Change an existing Target

  1. Open a CFG file
  2. Make all necessary changes. Maybe check the SNMP port number using the CheckPort feature.
  3. Save your edits.
  4. Run mrtg several times until all error messages are gone.
  5. Edit your crontab entries if necessary.
  6.  

Last updated: 07/16/98, by ibgm.