SNMP EXPLORER - A FREE APP FROM CPL SYSTEMS (c) 2013
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To install, extract and run the attached exe file.

SNMP Explorer is free to use and distribute with no support.

Use it to find any SNMP-enabled device on the network.

SNMP EXplorer contains over 100 preloaded MIB definitions.

All the control icons are in the top menu bar - hover to display a help bubble.

QUICKSTART HINT: at the opening screen click the AUTO DISCOVER icon in the toolbar at the top (3rd from the left). This will find any SNMP Agents in a specified ip range on your network.

How to use SNMP Explorer
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When SNMP Explorer starts, it will show nothing in either the MIB tree pane (left) or the MIB detail pane (right). You must set the name or IP address of the target SNMP agent system by clicking the top left icon. Once an agent is selected, you set the community name used by the agent with the 'Community Name' icon. The default community is "public". When the address and community have been set, click the 'Walk MIB' icon to 'walk (explore) the SNMP MIB'.

'MIB'= Management Information Base which basically tells us what the raw SNMP data values mean - eg. this value means temperature, that value means time etc.

MIB Walk
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During the MIB walk, we read the entire MIB from the agent into local memory. Then the retrieved MIB is formatted for viewing by loading it into the MIB tree pane and optionally the MIB detail pane. When formatting is completed, you can use either pane to explore the MIB.

You can switch between the tree driven MIB detail view and the full MIB dump view with the 'MIB Dump' icon. When MIB objects appear in the right pane (as opposed to containers) the last retrieved value for the object is shown. You can left click on the object to update the value and display the object's description below the detail pane.

Selecting the Agent System
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To select the Agent system whose MIB will be walked, click the 'Show SNMP Agents' icon (2nd from left). This will display a screen where you can enter the IP address or host name of the desired system. You can also select from previously entered values.

You can also click an icon to see a list of known Agent systems. If the list has not been populated, you will be prompted to perform an auto discovery scan of your network to locate available Agent systems. You can directly perform an auto discovery by clicking the  button.

Auto Discovery
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During an auto discovery, we send queries to the IP addresses in the range to be scanned to determine if a system exists at that IP address. We then check if it has an SNMP Agent available. The auto discovery screen shows any Agent systems found and you can then click on a system to select it for MIB walking.

Note that during auto discovery, only Agents whose community match the currently selected community name will respond to the discovery query.

Setting the Community Name
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The Community name is set by clicking the 'set community name' icon at the top. The Community name defaults to "public". The Community name acts like a password and is there to control access to SNMP Agents. Each Agent is configured with a Community name that it will respond to. The software has to supply the matching Community name to get a response from Agents.

MIB Display
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Once the Agent MIB has been walked, it is formatted for display. A tree view of the MIB is displayed in the left pane and the right pane reflects navigation through the tree. You can also navigate by clicking items in the right pane.

An SNMP MIB is a list of objects that represent actual data items that are tracked and reported by the Agent. These objects are organized into a hierarchy of containers or folders. Using the tree view and the detail view you navigate the MIB containers to locate the data object you are interested in. 

Data Objects
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When data objects are displayed in the right pane, thier name, data type and current value are displayed. You can click on the object to update the it's value (the Agent is queried) and display the detailed description of the object (if known) in the description pane (lower right).

There is an icon to toggle Full List mode. When Full List is turned on, the entire MIB is listed at the object level in the right pane. If you click on an object in the right pane, the tree view will be adjusted to show the location of the object in the container hierarchy.

OPTIONS SCREEN
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This screen allows adjustment of SNMP Explorer basic settings.

SNMP Get/Set Port
Sets the UDP port number that GET requests are sent on. 161 is the standard port.

SNMP Trap Send Port
Sets the UDP port number that Traps are sent on. 162 is the standard port.

SNMP Trap Listen Port
Sets the UDP port number that is used to listen for Traps. 162 is the standard port.

Timeout
Sets the timeout for GET requests in seconds.

SNMP TRAPS
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SNMP Traps are alert messages sent by Agents to Management applications. SNMP  Explorer supports both sending traps and receiving traps.

Sending Traps is mainly used to test other Management applications. You can send a Trap by clicking the 'send trap' icon. You are prompted for the IP address or name of the system where the trap will be sent, the Enterprise ID for the desired Trap family and the specific Trap number.

SNMP Explorer can act as a Trap manager. Click the 'enable trap' icon to enable receiving of Traps. Traps are received and logged for review. Click the 'Display Trap Log' icon to view the Trap Log.

Note that only one application may act as Trap Manager on a system. If any other Trap Manager, such as the Windows SNMP Trap Service is running, enabled Traps in SNMP Explorer will fail.

MORE ON MIBS
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A MIB or Management Information Base, is a data structure that defines the data objects exposed by an SNMP Agent. The basic entity in a MIB is an Object, or a unique identifiable data item. Objects are placed into a multi level hierarchy of containers to organize the many objects in a typical MIB in a logical manner.

The MIB in an Agent is defined by a schema language and stored in a text file. The schema itself is also called a MIB. This can be a bit confusing as the "MIB" for an agent is both a physical implementation in the Agent and a defintion or schema for that implementation stored in a text file. This is important because the schema or MIB file contains detailed descriptive information about the MIB objects and containers that are not stored in or reported by Agents.

A MIB object is idenfitied by a unique Object Identifier. The object further has a name, a data type, a textual description and a number of other attributes. Communication between and Agent and Management application is by the Object Identifier alone. When queried for an object or list of objects, and Agent will return the object identifier(s) and data values requested and nothing else. In order for a management application such as SNMP Explorer to present the Agent MIB in a useful manner, ie with container names, object names, data types (and appropriate formatting) and object descriptions, the manager must link the object ids returned by the Agent to object schema information stored in the MIB file.

It is for this reason that SNMP Manager applications ship with a set of MIB schema files. These files are compiled by the manager application so that it can present a useful view of the object data values returned by Agents.

SNMP Explorer ships with a set of common MIB files stored in the Mibs directory. Each MIB file is described in the MibRoot.txt file. When SNMP Explorer starts up, the MibRoot.txt file is loaded into memory so the SNMP Explorer knows what MIB files are available. MIB files themselves are not loaded at start up except for the set of files that describe the standard MIB object set required of all SNMP Agents.

As Agents are walked, SNMP Explorer will load MIB files as appropriate. A MIB file is not required to access an Agent but the descriptive information available about retrieved objects will be limited without a MIB file.

You can click an icon the to see a list of the MIB files that SNMP Explorer knows about and see which ones are loaded. You can force a MIB file to be loaded by clicking on it.

You can add your own MIB files to SNMP Explorer's list of MIBs. Place your files in the Mibs directory. Add a definition for your MIBs to the MibRoot.txt file. Then test against an Agent system to see if object names and descriptions appear.

The MibRoot.txt file contains defintions of MIB files in XML format. The format for a MIB file entry is described below:

<IBM-MIB load="auto" display="yes">
    <Module>IBM-MIB</Module>
    <RootId>1.3.6.1.4.1.2</RootId>

    <Desc>IBM Base MIB</Desc>
    <File>IBM-MIB.mib</File>
</IBM-MIB>

The <block-name  and </block-name elements define the start and end of a MIB file definition. The block-name is free but by convention is the same as the Module Name. The load attribute can be "yes" or "auto". Yes means the MIB will be loaded at start up time. Auto means the MIB will be loaded if needed. Always set the display attribute to "yes".

The <Module> element is the name of the MIB. This is found on the DEFINITIONS ::= BEGIN line at the top of the MIB file.

The <RootID> element is the Object ID of the highest Level item in the MIB.

The <Desc> element is a description of the MIB file and displayed on the MIB List screen.

The <File> element defines the name of the MIB file. This file is expected to be in the same directory as the MibRoot.txt file.

MIB definition blocks should be placed in the MibRoot.txt file in order sorted by the root object identifier. Out of order definitions may not be automatically loaded when the Agent is accessed.

When SNMP Explorer loads a MIB file, that MIB file is compiled based on the standards that describe the MIB schema language. If detectable errors occur, a window will appear describing the error. Due to limitations in the SNMP Explorer MIB compiler, some errors are not reported but cause the MIB to load incorrectly. If a MIB file loads without errors but does not display object names and descriptions correctly or seems to interfere with the correct operation of other MIBs, contact technical support for assistance.

MIB files typically import some number of objects or other defintions from other MIBs. If your MIB imports from other MIBs, those MIBs must be loaded before your MIB. In most cases, the MIBs typically imported are part of the standard set of MIBs delivered with SNMP Explorer (over 100) and will already be loaded.

(c)2013 CPL Systems



