HP Network Direr Software Products manual IP Ping Monitoring, Snmp MIB Data Retrieval

Key Concepts 277

The rate with which an active monitor polls depends upon the type of device that is being polled, the active monitoring mechanism used and the polling configuration.See “Using 3Com Network Director On A Multi-Site Network” on page 681 for more information.

Passive Monitoring: Passive monitoring relies upon a device monitoring its own state and sending unsolicited messages to 3Com Network Director whenever its state changes, providing details of the change.Passive monitoring uses SNMP traps to send this data.

As active monitoring relies upon regular polling, whereas passive monitoring only sends data when a device’s state changes, active monitoring generates more network traffic than passive monitoring. However, active monitoring is a more reliable and deterministic means of monitoring the status of network devices.

IP Ping Monitoring

The simplest monitoring technique used by 3Com Network Director is IP ping monitoring.This is an active monitoring technique that works by 3Com Network Director sending an ICMP ping message to the device being monitored and using the response time, or lack of a response, to update the state of the monitor it is being used for.

SNMP MIB Data Retrieval

Many network infrastructure devices maintain statistics about their operation, which may include such details as the number of packets sent and received on each port or the status of their components, and allow access to this information via SNMP MIBs.When 3Com Network Director is monitoring a device or link using an SNMP MIB-based monitor, 3Com Network Director uses SNMP v1 to request particular MIB values on a regular basis.The information returned from the device’s MIB is then used, sometimes in conjunction with previously retrieved information, to update the state of the monitor.

SNMP MIB data retrieval is an active monitoring technique.

A particular SNMP MIB-based monitor may rely upon a single MIB value or multiple MIB values.3Com Network Director optimizes its retrieval from devices so that it only retrieves those MIB values relevant to the monitors that are currently running.For more details on how to restrict monitoring to only those monitors that you are interested in see “Disabling and Enabling Individual Monitors” on page 294.