Configuring maximum number of repetitions for GetBulk requests

The GetBulk command is used to retrieve all the rows of a table from a network resource, for example, to retrieve all the rows in a routing table from a router. The max-repetitions parameter indicates how many rows of the table are to be retrieved in a single GetBulk operation. You can adjust the GetBulk configuration settings to minimize the number of packets exchanged as part of the GetBulk operation.

About this task

The SNMP Helper determines the value of the maximum number of repetitions for GetBulk requests (the max-repetitions parameter) based on the following calculation:
max-repetitions = DefaultGetBulkMaxReps / #varbinds
Where:
  • The DefaultGetBulkMaxReps property is defined in the $NCHOME/etc/precision/NcPollerSchema.cfg file. The default value is 20. This property defines the number assigned to the max-repetitions field in GetBulk requests issued by Network Manager processes. The value 20 is used when the GetBulk request contains a single varbind. If multiple varbinds are included, then the value is adjusted accordingly (divided by the number of varbinds), so that responses always contain a similar number of varbinds.
  • #varbinds is the number of variable bindings being requested. In the SNMP Helper, this value is usually 1. However, the value can vary depending on where the SNMP Helper is being deployed and on the following factors:
    • In the Discovery engine, ncp_disco, the #varbinds value can vary depending on the code in the discovery agent.
    • In the Polling engine, ncp_poller, the #varbinds value can vary depending on which MIB objects are included in the poll definition.

Procedure

  1. Edit the following configuration file: $NCHOME/etc/precision/NcPollerSchema.cfg.
    Note: You can make the NcPollerSchema.cfg file domain specific by copying it to $NCHOME/etc/precision/NcPollerSchema.DOMAIN_NAME.cfg, where DOMAIN_NAME is the name of the domain.
  2. Find the line that defines the value of the DefaultGetBulkMaxReps property.
  3. Change the value assignment for the DefaultGetBulkMaxReps property.
  4. Save the file $NCHOME/etc/precision/NcPollerSchema.cfg.
  5. Restart the Polling engine, ncp_poller to activate the configuration changes.