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Description

Domain Concepts

SNMP facilitates communication between a managed device (an SNMP agent, e.g. a router), and an SNMP manager or management application (used by a network manager). Communication is via SNMP protocol data units (PDUs), and essentially four kinds of operations are permitted between managers and agents. These are :


User Interface

This section provides a detailed description of the SNMP Main Screen layout. It provides the user step-by-step instructions to use each of the Main Screen components.

tocSNMP Main Screen

The SNMP Main Screen is as shown in Figure 1.

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Figure 1 - SNMP Main Screen

The following are the Main Screen components :


{short description of image}Community

Community - is a grouping of agents and managers. There can be many such communities. Each community is represented by a name. In Figure 1, publicis the community name(default and widely used) which represents a set of managers and agents.


{short description of image}Object

Object - An Object is a network resource managed by the network manager. Following is a brief description of a sample of Objects :

  1. SysDescr- gives the system description (hardware and software details) of the agent.
  2. SysLocation- displays where the system is located.
  3. SysName- displays the name of the system.
  4. SysUpTime- displays the period of time the system has been on.

Refer to Figure 2 for a drop-down list of Objects.

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Figure 2 - Objects drop-down list

To Create New Objects

  1. Select the browse {short description of image} button of the Object field from the Main Screen.
  2. This displays the Object Selector dialog box as shown in Figure 3.
  3. Enter the new Object name.
  4. Enter the Object Identifier.
  5. Object Identifier should always be prefixed with "1.3.6.1.2.1.".
  6. Select the Object Type from the drop-down list box.
  7. Click on  Add button.
  8. Select the OK button to close theObject Selector dialog box and continue with the Object creation operation.
  9. Select the Cancel button to close the Object Selector dialog box and discontinue the Object creation operation.
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Figure 3 - Object Selector dialog box

To Delete an Object

  1. Select the browse {short description of image} button of the Object field from the Main Screen.
  2. This displays the Object Selector dialog box as shown in Figure 3.
  3. Select an Object from the Object-list in the Object Selector dialog box.
  4. Click the Delete button.
  5. Select OK button to complete the deletion of the object.
  6. Select Cancel button to discontinue the delete operation.

To Modify an Existing Object

  1. Select the browse {short description of image} button of the Object field from the Main Screen.
  2. This displays the Object Selector dialog box as shown in Figure 3.
  3. Select the Object to be modified from the Object-List.
  4. Select the Edit  button.
  5. This displays the details of the Object.
  6. Edit the contents and select the Update button to effect the changes made.
  7. Select OK to save the changes made.
  8. Select Cancel to discontinue the modify operation.
object file
Figure 4 - Object File dialog box

{short description of image}Note : The Objects are stored in an Object file which must have a .snm extension. While Adding/Deleting/Editing an Object, when the OK button is selected, if the Object file has not been specified previously (using the property sheet for the component), the Object File dialog boxas shown in Figure 4 appears.


{short description of image}Agent

An Agent is a processing entity which belongs to one or more communities .

To Create a New Agent

  1. Select the browse {short description of image} button of the agent field from the Main Screen.
  2. This displays the Agent Selector dialog box as shown in Figure 5.
  3. Enter the Agent name.
  4. Enter the IP address of the agent.
  5. Select the OK button to close the Agent Selector dialog box and continue with the creation operation.
  6. Select Cancel button to close the Agent Selector dialog box and discontinue the creation operation.
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Figure 5 - Agent Selector dialog box

To Delete an Agent

  1. Select the browse {short description of image} button of the agent field from the Main Screen.
  2. This displays the Agent Selector screen as shown in Figure 5.
  3. Select an Agent from the Agent-list.
  4. Click the Delete button of Agent Selector dialog box.
  5. Select OK button to save the changes made.
  6. Select Cancel button to discontinue the delete operation.

To Modify an Existing Agent

  1. Select the browse {short description of image} button of the agent field from the Main Screen.
  2. This displays the Agent Selector dialog box as shown in Figure 5 .
  3. Select the Agent to be modified from the Agent-List.
  4. Click the Edit button. This displays the details of the Agent.
  5. Edit items you wish to modify.
  6. Edit the contents and select the Update button to effect the changes made.
  7. Select OK to save the changes made.
  8. Select Cancel to discontinue the modify operation.
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Figure 6 - Agents File dialog box

{short description of image}Note : The Agents are stored in an Agents file which must have a .snm extension. While Adding/Deleting/Editing an Agent, when the OK button is selected, if the Agent file has not been specified previously (using the property sheet for the component), the Agents File dialog box as shown in Figure 6 appears.


{short description of image}SNMP Main Screen Buttons

The Main Screen contains four buttons: GetRequest, GetNextRequest, SetRequest and Clear Log button for the main operations.

GetRequest gets the status of the specified Object from the specified Agent. e.g. to know how long the Agent has been up and running.

  1. Select SysUpTime from Object-list .
  2. Select the Agent for which the SysUptime is to be found from the Agent-list.
  3. Click the GetRequest button.

GetNextRequest - This button is used to get the value of an Object which is lexicographically next in the Management Information Base in the Agent. e.g. the button could be used to get the entries of a table-entry one-by-one. If the System table contains SysDescr, SysObjectID, SysUpTime, SysContact, etc., each time GetNext button of Response - GetNextRequest dialog box is clicked the respective details are displayed. An entire table can be traversed by using GetNextRequest button.

When the GetNextRequest button is clicked the Response - GetNextRequest dialog box as shown in Figure 7 appears. The Response - GetNextRequest dialog box contains the response area, which displays the requested information. When the OK button is clicked the Response - GetNextRequest dialog box is closed. When GetNext button is clicked the lexicographically next Object in the MIB is retrieved and displayed.

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Figure 7 - Response-GetNextRequest dialog box

SetRequest can be used to change an existing Object’s value, e.g. to change the system name :

  1. Select the Object from the Object-List of the Main Screen.
  2. Click the SetRequest button.
  3. This displaysEnter Value dialog box as shown in Figure 8 is displayed.
  4. Type the Object Value whose type matches the one specified in the Object Type field.
  5. Click OK button to continue with the SetRequest operation
  6. Click Cancel button to discontinue the SetRequest operation.
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Figure 8 - Enter Value dialog box

Clear Log can be used to clear the contents of the response area.


{short description of image}Response

Response area displays all the requested information. The Response area also logs status information in the form of errors received from an Agent. The Response area can be cleared by clicking the Clear Log button.

When the request is valid, the response is as shown in Figure 9.

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Figure 9 - Response Screen

When the request is invalid the response is as shown in Figure 10.

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Figure 10- Response Screen

If the SNMP agent sends an unknown object identifier (not present in the Objects file), then the GetNext operation fails the message as shown in Figure 11 is displayed.

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Figure 11 - Response Screen

{short description of image}Trap

The SNMP Agent uses traps to report extraordinary events to the Network Manager. It is an asynchronous notification. When a Trap is received a Trap Response dialog box as shown in Figure 12 appears.

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Figure 12 - Trap Response dialog box

Enterprise OID - It contains the type of object generating the trap

Sending Agent - Value of the agent’s network address

Generic Trap - Contains information about certain unusual events, for e.g. "Generic Trap : Authentication failure" means that the manager is not authenticated to access the Agent

Specific Trap - Enterprise specific trap which is specific to set of Agents and Managers

Time Stamp - The value of the SystemUpTime on Agent side

Some other information about the Trap

Information OID - The Object Identifier carrying the information

Information Value - The Information OID’s Value