Health and performance monitoring can benefit from the remote monitoring of SNMP variables by the local SNMP agents running on each router. The SNMP agents compare MIB values against predefined thresholds and generate exception alarms without the need for polling by a central SNMP management platform. This is an effective mechanism for proactive management, as long as the thresholds have baselines determined and set correctly. For more information, see RFC 2819, Remote Network Monitoring MIB.
This topic includes the following sections:
By setting a rising and a falling threshold for a monitored variable, you can be alerted whenever the value of the variable falls outside of the allowable operational range. (See Figure 4.)
Figure 4: Setting Thresholds
Events are only generated when the threshold is first crossed in any one direction rather than after each sample period. For example, if a rising threshold crossing event is raised, no more threshold crossing events will occur until a corresponding falling event. This considerably reduces the quantity of alarms that are produced by the system, making it easier for operations staff to react when alarms do occur.
To configure remote monitoring, specify the following pieces of information:
Before you can successfully configure remote monitoring, you should identify what variables need to be monitored and their allowable operational range. This requires some period of baselining to determine the allowable operational ranges. An initial baseline period of at least three months is not unusual when first identifying the operational ranges and defining thresholds, but baseline monitoring should continue over the life span of each monitored variable.
The JUNOS software provides two mechanisms you use to control the Remote Monitoring agent on the router: command-line interface (CLI) and SNMP. To configure an RMON entry using the CLI, include the following configuration statements at the [edit snmp] hierarchy level:
- rmon {
-
- alarm index {
- description;
- falling-event-index;
- falling-threshold;
- intervals;
- rising-event-index;
- rising-threshold;
- sample-type (absolute-value | delta-value);
- startup-alarm (falling | rising | rising-or-falling);
- variable;
- }
-
- event index {
- community;
- description;
- type (log | trap | log-and-trap | none);
- }
- }
If you do not have CLI access, you can configure remote monitoring using the SNMP Manager or management application, assuming SNMP access has been granted. (See Table 26.) To configure RMON using SNMP, perform SNMP Set requests to the RMON event and alarm tables.
Set up an event for each type that you want to generate. For example, you could have two generic events, rising and falling, or many different events for each variable that is being monitored (for example, temperature rising event, temperature falling event, firewall hit event, interface utilization event, and so on). Once the events have been configured, you do not need to update them.
Table 26: RMON Event Table
The RMON alarm table stores the SNMP object identifiers (including their instances) of the variables that are being monitored, together with any rising and falling thresholds and their corresponding event indexes. To create an RMON request, specify the fields shown in Table 27.
Table 27: RMON Alarm Table
Both the alarmStatus and eventStatus fields are entryStatus primitives, as defined in RFC 2579, Textual Conventions for SMIv2.
You troubleshoot the RMON agent, rmopd, that runs on the router by inspecting the contents of the Juniper Networks enterprise RMON MIB, jnxRmon, which provides the extensions listed in Table 28 to the RFC 2819 alarmTable.
Table 28: jnxRmon Alarm Extensions
Monitoring the extensions in this table provides clues as to why remote alarms may be not behave as expected.
 | Copyright © 2009, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |