MIB Browser Applet Overview Version 1.2

Introduction

You will need to understand a little bit about SNMP before you can make sense of this document.

MIB Browsers allow the user to view and operate on data available through an SNMP agent on a managed device, e.g. a router. In order to enable a better view of the data available on the SNMP agent a MIB file is usually provided with the managed device. This MIB file contains a description of the object hierarchy on the managed device, as well as the syntax and access privileges for each variable in the MIB.

The Advent MIB Browser provides the capability to load and view multiple MIB modules, and traverse the MIB tree to look at the definitions for each node in the MIB tree. It allows "GET," "GETNEXT," and "SET," SNMP requests to a particular variable in the MIB of an SNMP managed device. It also provides the capability to view multiple real-time graphs of data on the managed device as it changes over time. It also enables viewing SNMP tables.

MIB Browser Primary Display

The primary window of the MIB browser applet is shown below. This is a snapsot from Appletviewer on Windows 95, but it looks similar in Netscape and on Java enabled browsers. It includes fields for community, SNMP agent name or address (Host), value used for a set request, the current Node OID that's being operated upon, a chooser for the current MIB module, a list of children of the current node, and a text area to view query results.

The operations allowed with the MIB browser are available through the series of buttons at the bottom of the applet's main window.

Loading a MIB

The loading of MIB modules is via URLs. A few MIB modules are provided with the Advent browser , i.e. rfc1213-MIB, rfc1271-RMON and rfc1155-SMI, but you can choose to load any other MIB modules. It may be convenient to copy your MIB module files to be loaded into the MIB browser applet directory.

The MIB browser applet has a button Load Mib which should be selected to bring up a MIB dialog, which prompts you for the URL of the MIB module file you wish to load. If you have copied the file into the MIB browser applet directory, you can just type the file name. If not, type the absolute or relative URL to be loaded. This may not work if you're trying to read a MIB module on some host that's not the applet host because of browser security.

You can load multiple modules and use the choice item to specify any one of them as the current module at any time. When any MIB module is selected, the root node for that module becomes the current OID. You cannot move up beyond the root of a MIB module, and will need to choose the module you want to browse in to move across modules.

Getting and Setting SNMP Variables

To fully specify an object to an SNMP agent, both the Object ID (which defines the type of object) and the instance (the specific object of the given type) need to be provided. From the MIB you get the Object ID, to which an instance needs to be added to completely identify the object of interest. For non-tabular (or scalar) objects this is simply an instance of 0 (e.g. sysDescr.0). For tabular objects the instance is defined by the MIB, and is a sequence of one or more variables (e.g. ifInOctets.2 or tcpConnState.179.74.15.126.1192.225.226.126.197.80).

In order to graph and set SNMP variables, you will need to completely specify the Object ID plus instance. However, you can use getnext, and specify just the Object ID from the MIB (e.g. sysDescr), and get the first instance of that type from the SNMP agent. This works for all types of objects.

Select a MIB node of interest to you, and either select getnext, or add the instance you're interested in at the end of the OID and use get. Once you have the correct instance, you can graph it and use set as well.

You will also need to specify the hostname and community streing of the SNMP agent you're talking to in the appropriate field.

Viewing Real-time Graphs

Before using the Graph button, the agent hostname or IP address and a valid OID need to be specified. The OID needs to be an integer or unsigned integer (Counter, Gauge or Timeticks) and include the instance being graphed. If you're browsing the MIB tree, ensure you get the required instance by using the Get Next button, before clicking on graph.

You can bring up multiple graphs showing different variables from different hosts. A sample graph is shown below.

The above graph shows the number of packets coming in on the PPP connection on my Windows 95 PC as I'm browsing the Web. The SNMP agent in this case is the one that comes with Windows 95. The graph below is the throughput I'm getting with a file transfer over my 28.8 K link. The polling for the graph is done every 15 seconds. The throughput below is in Bytes/sec since we're averaging over the polling interval.

Help and Debugging Output

The Help button brings up a window which prints a short help message, and debugging output. As long as this window is opened, debugging is turned on, and debugging output is generated. When you close this window debugging is turned off.

Starting the MIB Browser

To fully use the Advent MIB Browser applet, you will need the Java Development Kit (JDK) from Sun Microsystems or a Java enabled browser like Netscape, and run in one of the following configurations

Download

You need to get the MIB Browser classes and the Advent SNMP classes via the above link.

Problems?

We'd like to get reports on any problems you're having using the browser. We'd suggest you to check the FAQ and other documentation first, and then send in a problem report to us at bug-report@adventnet.com if you do not find a solution in the documentation. Please include as much information as you have on the problem. We will endeavor to get back to you with an answer. The mailing list would be another good resource for getting any problems resolved.