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The discovery mechanism enables you to force the discovery of specific devices or to discover devices with specific port and agent, before discovering any other devices in the network.
Forcing Discovery of IP Addresses in a Network
To force the discovery of specific nodes (before discovering any other device in the network)
Click the Node Discovery tab in the Discovery Configurator.
Select Discover.
Enter the IP address of the device that is to be discovered and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Click Add. The IP Address and NetMask will be added to the table above the fields with the Discover column being enabled (checked), that is, discovery of those nodes are enabled. If it is unchecked then the node will be ignored/undiscovered. Multiple IP addresses can also be configured.
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Note: If the network corresponding to the given address is not available in the topology database, then the discovery engine will first add the network object to the database and will discover the specified IP before adding any other node in the network. |
Discovering Nodes from Local Network (which is disabled)
There is a provision to discover nodes from the local network, where the discovery of local network option is disabled. Refer to Preventing local network from being discovered in General Parameters Configuration.
Example screen shots of Local Network being disabled and Node to be discovered configurations are shown below:
The above configuration can be performed to discover and add the local network and the node 192.168.4.10 (if the local network is 192.168.4.0 and is disabled).
By default, when a device is discovered in the network, its parent network is also discovered, that is, other devices in that network is also discovered.
To prevent discovery of parent network
Click the Node Discovery tab in the Discovery Configurator.
Select Discover.
Enter the IP address of the device that is to be discovered and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Uncheck Discover Parent Net.
Click Add.
Discovering SNMP Devices with Specific Community and Agent Port
By default, WebNMS discovery uses the community string public and the agent port 161 while discovering SNMP devices. But some devices in the network could use a different port and community.
To discover SNMP devices with specific community and port
Click the Node Discovery tab in the Discovery Configurator.
Select Discover.
Enter the IP address of the device that is to be discovered and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Choose the SNMP version v1, v2, or v3 from SNMP Version drop-down box.
Enter the community of the device in Community field. Default value is public.
Enter the SNMP agent port of the device in SNMPAgentPort field. Default value is 161.
Discovering SNMPv3-Enabled Devices
SNMPv3 discovery for specific devices is useful under the following two situations:
a) In a network where only selected devices are SNMPv3 devices, sending v3 queries for all the devices would be redundant. Hence, only selective devices should be configured for v3 discovery. The following are the configurations to be made for this situation.
Click the Protocol tab in the Discovery Configurator.
Select SNMP and click Properties. The SNMP Properties dialog box is displayed.
Disable SNMPv3 Discovery if already enabled and click OK.
Click the Node Discovery tab in the Discovery Configurator.
Select Discover.
Enter the IP address of the device that is to be discovered and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Choose v3 from SNMP Version drop-down box.
Enter the security user name, context name and the port number in the UserName, ContextName, and SNMPAgentPort fields respectively.
Click Properties. The SNMP v3 Properties dialog is invoked.
Enter appropriate values in the fields available.
Click OK.
Click Add.
In this setup, the discovery engine will send SNMP v3 queries only to devices that are specified in the IPAddress with SNMP Version set as v3. If the v3 queries to these devices fail, then v2 and v1 queries are sent to the devices. If any of these succeeds, the device will be added to the appropriate version set to it.
b) Also for a particular device, if the common username and contextname specified should not be used and you want to override the common configurations specified for this device, you can use this device-specific v3 configuration. The configurations to be made for this situation are:
Click the Protocol tab in the Discovery Configurator.
Select SNMP and click Properties. The SNMP Properties dialog box is displayed.
Enable SNMPv3 Discovery if already disabled.
Enter the User Name, Context Name, and SNMP_Ports and click OK.
Click the Node Discovery tab in the Discovery Configurator.
Select Discover.
Enter the IP address of the device (for those devices whose v3 configurations should be overridden) and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Choose v3 from SNMP Version drop-down box.
Override the common configurations by entering values for UserName, ContextName, and SNMPAgentPort fields.
Perform steps 9 to 12 as explained in previous section.
It is enough if you override the necessary properties alone. The values of those properties that are not specified in the Node Discovery tab will be taken from the common values.
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Note: During discovery, sometimes the SNMPv3 devices are discovered as SNMPv2 devices. This occurs when the timeout or retries value is less. Hence to avoid this, set the SNMP Timeout or the SNMP Retries more than the default optimal value based on your agent's performance. These values can be configured in Initial Parameters. |
Preventing Discovery of IP Addresses in a Network
The discovery engine can also be configured to prevent the discovery of certain IP addresses in a network.
To prevent the discovery of a device: Procedure 1
Click the Node Discovery tab in the Discovery Configurator.
Disable Discover (not selected).
Enter the IP address of the device (for those devices whose v3 configurations should be overridden) and netmask of the device in IPAddress(es) and NetMask fields respectively. Both these fields are mandatory.
Click Add.
To prevent the discovery of a device: Procedure 2
This procedure is applicable only if the device is already configured and displayed in table above the fields.
Select the row that represents the required device in the table.
Disable Discover option.
Click Modify.
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