Router traffic data collection

Routers connect networks and route traffic among them. Following are examples of how you might configure the interface to monitor routers in typical scenarios.

Under SNMP, the interfaces in a router are indexed by an Object Identifier (OID) called ifIndex. This index is a positive integer that enables you to reference and correlate other interface OID variables (for example, interface speed). The SNMP agent on the router automatically assigns the value of ifIndex. The value of ifIndex does not have to start at 1, and the indexes are not necessarily consecutive. The value of the OID variable interfaces.ifTable.ifEntry.ifSpeed.X (where X is an ifIndex value) is expressed as bits per second.

To determine the amount of traffic that is traversing a particular interface and index, monitor the values of the following OID variables:

• interfaces.ifTable.ifEntry.ifEntry.ifInOctets.X

  The total number of octets (a group of 8 bits) received on the interface, including framing characters.

• interfaces.ifTable.ifEntry.ifEntry.ifOutOctets.X

  The total number of octets transmitted on the particular interface, including framing characters.

These OID variables indicate the total number of octets received or transmitted. However, you might want to track the number of octets per second received or transmitted by the interface. To configure a point that records rate, set its location2 attribute to 1. The PI SNMP Tag Builder plug-in for PI SMT 3.x automates much of the configuration required for such monitoring. Consult the plug-in documentation for details.