Configuring Informs

• Overview

• Enabling/Disabling Inform Service

• Configuring Informs

• General Parameters

• Request-based Parameters

• Threshold-based Parameters

• Timer-based Parameters

• Adding Varbinds

• Sending Informs

• Modifying and Deleting Informs

• Viewing Inform Response

Overview

SNMP Notifications can be sent as Traps or Inform requests. Traps are unreliable because the Manager does not send any acknowledgment on receiving the Trap. So, the Agent cannot determine if the Trap was received by the Manager. However, an SNMP Manager that receives an Inform request acknowledges the message with an SNMP response PDU.  If the Manager does not receive an inform request, it does not send a response. If the Agent does not receive a response at all, the inform request can be sent again.

You can generate SNMPv2c and SNMPv3 Informs, on the following conditions:

• Request-based Informs

• Threshold-based informs

• Timer based informs

Enabling/Disabling Inform Service

he SNMP Agent Simulator and Network Simulator provides option to enable/disable the execution of  Informs configured in the simulator, at agent runtime. If inform service is disabled, the agent will not check for inform configurations before sending the response. Hence, you can use this option to improve the performance of the SNMP agent, if informs are not required to be executed. By default, the service is enabled and the informs configured (if any), will be executed.  

To disable the service in SNMP Agent Simulator,

• Select Operations -> Initialize Services. The Initialize Service dialog is displayed.

• Deselect the option Enable SNMP Inform Service.

• Start the Agent. Now, the informs configured in the simulator, will not be executed.

To disable the service in Network Simulator,

• Select Run -> Initialize Services. The Initialize Service dialog is displayed.

• Deselect the option Enable SNMP Inform Service.

• Start the Agent. Now, the informs configured in the network simulator, will not be executed.

Configuring Informs

Request-based informs are informs that are generated when a request ( Get and Set / Set only ) is made by the Manager on the simulated agent. Thus, Request-based informs will be triggered if there is a GET / SET operation from the manager on the specified OID. The Inform variable is a unique identifier based on which the configured inform will be identified.

You can configure request-based, timer-based and threshold-based informs from the SNMP Agent Simulator and Network Simulator.  To configure the same,

1. Choose the option Configure --> Informs from the menu bar or click on the Configure Informs icon in the tool bar. The Configure Inform Requests dialog is displayed.  In Network Simulator, you can also right-click on a device and select SNMP --> Informs.

2. To configure a new inform request, click Add . The Add/Modify Inform Request dialog is displayed.

3. Configure the General Parameters that are common for Request-based, Response based and Timer based Informs

4. To configure Request-based Informs, specify Request-based Parameters.

5. To configure Threshold-based Informs, specify Threshold-based Parameters.

6. To configure Timer Based Informs, specify Timer-based Parameters.

General Parameters

1. • Variable : The trap variable or associated variable is a unique identifier. When an SNMP operation is performed on this variable, it will trigger the Inform. Browse and select the required scalar/columnar node from the MIB tree and click OK. The OID of the selected node will be displayed as the Inform variable.

   • Instance : All the available instances of the selected associated variable (node) will be shown in the drop down box. For scalar nodes, the instance field will be disabled with its default value zero.

   • Version :  SNMP v2c and v3 Informs are supported. If the inform version is v3, the v3 agent must be started and the user name and context name of the v3 user must be specified. Refer the topic, Simulating a V3 agent, to know more about starting the v3 agent, the default user names and password, and configuring new user names and password.

   • Manager Name : Specify the manager name. If the Manager is running on the same machine it will contain the value localhost. If the Manager is running on a different machine specify the manager name or IP address of that machine.

   • Manager Port : The default manage port is 162. If the manager is running on a different port, specify the port number.

   • Community : Specify the community name of the manager.

   • Varbinds : There are two OIDs that are default varbinds in Inform. They are sysUpTime and snmpTrapOID. In addition to this, you can add extra varbinds. It is optional. To know more about adding Variable Bindings, refer the topic Adding Varbinds.

Request Based Parameters

Request based informs are informs that are generated when a request ( Get and Set / Set only ) is made by the Manager on the simulated agent. To configure Request based parameters, enter the following details in the check boxes :

1. • Generate for : The simulated inform needs an operation ( Get or Set ) on a MIB node. This will be the trigger based on which the informl be generated when any request is made on the selected OID on which the operation will be performed. Choose the Request type from the following options:

   • • Generate inform on Get & Set

     • Generate inform on Set only.

   • Time Interval : You can also specify the time interval between the informs that are to be sent. The time interval option is available in milliseconds. Eg: 1000 Milliseconds. It is optional.

   • Number of times inform should be sent : Specify the number of informs that you want to send. Eg: 100. It is optional. If you leave this field blank, the informs will be generated infinitely.

   • Click OK to add the Request based inform.

Configuring Threshold-based Informs

Threshold-based informs are generated when the value in the selected OID satisfies the specified threshold condition and the threshold value. Thus, when the threshold condition is satisfied the inform will be sent. The Inform variable is a unique identifier based on which the configured inform will be identified

1. • Generate for : Select Generate Inform based on Threshold. Specify the threshold condition and value based on which the inform will be sent.

   1. • Threshold Condition : The threshold conditions listed depend upon the type of the selected inform variable. For a node of type Octet String, Object ID and IP Address, the conditions displayed are :

      • • • Equal To

          • Not Equal To

      • For types other than Octet String, Object ID and IP Address, the following threshold conditions are listed:

• • • • Equal To

      • Not Equal To

      • Greater than

      • Less than 

      • Custom In Range: For Custom In Range, a trap will be sent if the value of the associated trap variable is within the lower and upper threshold value which includes the lower and upper threshold value. For example, if the lower threshold value is 10 and upper threshold value is 20, a trap is sent if the associated trap variable value is equal to 10 or equal to 20 or any values within the range 10 to 20. 

      • Custom Out Range: For Custom Out Range, a trap will be sent if the value of the associated trap variable is not within the lower and upper threshold value which includes the lower and upper threshold value. For example, if the lower threshold value is 10 and upper threshold value is 20, a trap is sent if the associated trap variable value is not equal to 10 or not equal to 20 or any values not within the range 10 to 20.

• Threshold Value : Specify the threshold value. For custom range options both the lower threshold value and higher threshold value must be specified.

• Time Interval : You can also specify the time interval between the informs that are to be sent. The time interval option is available in milliseconds. Eg: 1000 Milliseconds. It is optional.

• Number of times inform should be sent :Specify the number of informs that you want to send. Eg: 100. It is optional. If you leave this field blank, the informs will be generated infinitely.

• Click OK to add the Threshold-based inform.

Configuring Timer-based Informs

Timer-based informs are generated at the configured time. In timer-based informs, the OID uniquely identifies the configured informs. Thus, when the timer condition is satisfied the inform will be sent. The Inform variable is a unique identifier based on which the configured inform will be identified.

1. • Generate for : Choose Generate Informs based on timer. Specify the timer configurations.

   • • Staring Time : The simulator will start sending Informs at the configured time. You can use the spinner control to set the time.

     • Time Interval: You can also specify the time interval between the Informs that are to be sent. The time interval option is available in milliseconds. Eg: 1000 Milliseconds.

     • Number of Informs: Specify the number of Inform that you want to send. Eg: 100

   • Click OK to add the Inform.

Adding Varbinds

Variable Bindings or Varbinds is an additional information that is sent to the manager along with the trap or inform.. It can be value of the selected MIB nodes. This value is sent to the manager along with the trap or Inform. The Varbinds dialog can be invoked from the add/modify trap dialog and also from the trap configuration dialog .

The following options are provided to configure varbinds for inform messages,

1. • sysUptime: Configure  the required sysUptime value to be sent with the inform response.

   • snmpTrapOid: Configure the SNMP trap oid to be sent with the inform response.

   • To add additional varbinds, click on the Varbinds button. The Varbinds dialog pops up.

   • Select a varbind (only leaf nodes) in the MIB tree and click Add. The Configure Varbinds dialog pops up with the OID and instance of the selected varbind.

   • You can specify the varbind value with any one of the following options :

   • Agent Value  : Agent value refers to the value of the node configured in the simulated agent.

   • Agent Macro :  The following agent macros are supported:

   • •  SysUpTime: Selecting this macro will  return the sysUpTime value of the agent as the varbind value.

     • CurrentTime: Selecting this macro will return the current time as the varbind value.

   • Custom Value : If custom value is selected, the value must be specified in the appropriate format based on the selected node.

   • Click OK to add the varbind(s).

To modify varbinds,

1. • Select the added varbind and click Modify.

   • Make the necessary changes in the Configure Varbinds dialog appears.

   • Click Ok to add the varbind with modified values.

To delete varbinds ,

1. • Select the varbind from the list and click Delete to remove the varbind.

Sending Informs

The informs configured in the Configure Inform Request dialog, can be sent in the following ways.

Using Send Button

By using the Send button in the dialog, you can select and send any inform irrespective of the condition configured. The selected informs will be sent to the specified manager at the port specified.

Sending Request Based Informs

Request Based Informs are generated when a request is made on the configured node. For example : A request based inform is configured with the following values with other options as default.

Associated variable is sysUpTime of the RFC1213-MIB with OID .1.3.6.1.2.1.1.3
Trap Version is Snmp V2c
Request Type is Generate Inform on Get and Set.
Time Interval is 2000 milliseconds.
Number of times inform should be sent is 5

When a Get/Setrequest is made from the Manager, on the variable sysUpTime, 5 SNMP v2c informs with default varbinds, will be generated with a time interval of 2 seconds between the informs. The informs will be sent to the managers running at the specified ports. The inform responses can be viewed from the Inform Response tab of the Configure Inform Requests dialog.

Sending Threshold Based Informs

Threshold-based Informs are generated when the selected OID satisfies the specified threshold condition and the threshold value. For example : A Threshold-based inform is configured with the following values with other options as default.

Variable is ifAdminStatus of the IfTable of RFC1213 MIB with OID .1.3.6.1.2.1.2.2.1.7
Version is Snmp V2c
Threshold Condition is Equal To
Threshold Value is 2
Time Interval is 5000 millisecods
Number of times inform should be sent is 10

If the value of the OID .1.3.6.1.2.1.2.2.1.7 equals to 2, 10 SNMP v2c informs with default varbinds , will be generated with a time interval of 5 seconds between the informs. The informs will be sent to the managers running at the specified ports. The inform responses can be viewed from the Inform Response tab of the Configure Inform Requests dialog.

Sending Timer Based Informs

Timer-based informs are generated at the configured time. For example : A timer-based inform is generated with the following values, with other options as default.

Variable is sysName of the RFC1213-MIB with OID .1.3.6.1.2.1.1.5 .In timer informs, the OID is specified to uniquely identify the inform.

Version is Snmp V2c
Starting Time is 20 - Mar 2003 ; 17 : 00 : 00
Time Interval is 5000
Number of times inform should be sent is 10

When the specified date and time is reached (20 th Mar, 2003 at 17 hrs) , 10 SNMP v2c informs with default varbinds, will be generated with a time interval of 5 seconds between the informs. The inform will be send to the managers running at the specified ports. The inform responses can be viewed from the Inform Response tab of the Configure Inform Requests dialog.

Viewing Inform Response

When informs are sent, the SNMP Manager that receives the Inform request acknowledges the message with an SNMP response PDU.

To view the inform response from SNMP Agent Simulator,

• Choose the option Configure --> Informs from the menu bar or click on the Configure Informs icon in the Tool bar. The Configure Inform Requests dialog is displayed.

• Select the Inform Response tab. The response received from the SNMP Manager, will be listed in the table.

• To clear all the responses, click Clear.

• To close the dialog, click Close.

To view the inform responses from the Network Simulator,

To view the inform response of a specific device:

1. 1. • Right-click on a device and select SNMP -> Informs or choose the option Configure --> Informs from the menu bar. The Configure Inform Requests dialog is displayed.

      • Select the Inform Response tab. The response received from the SNMP Manager for the selected device, will be listed in the table.

      • To clear all the responses, click Clear.

      • To close the dialog, click Close.

To view the inform response from all the devices:

1. 1. • Select Tools -> Inform Response. The Inform Response dialog displays the inform responses for all the devices which sent the inform messages.

      • To delete a specific entry, select the entry and click Delete.

      • To close the dialog, click OK.

Modifying and Deleting Informs

You can modify an existing inform to change the configured values.

• Click on the Inform icon in the Tool bar or choose Configure --> Inform from the menu.

• The Inform Configurations dialog is brought up, displaying the Informs configured.

• Select the Inform that you want to modify from the displayed list.

• Click Modify to make all the necessary modifications.

• Click OK

You can delete existing informs from the Configure Inform Requests dialog.

• Choose the Configure --> Informs from the menu bar or click on the inform icon in the tool bar. The Inform Configurations dialog is brought up, displaying the informs configured.

• Select the inform that you want to delete and Click Delete. The selected informs will be deleted.