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Remote Monitoring (RMON) is a standard monitoring specification that enables various network monitors and console systems to exchange network-monitoring data.
RMON delivers information in RMON groups of monitoring elements, each providing specific sets of data to meet common network-monitoring requirements.
This module describes the features of the RMON Alarm group and the RMON Events group, and explains how to configure RMON events and alarms.
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Remote Monitoring (RMON) is a standard monitoring specification that enables various network monitors and console systems to exchange network-monitoring data.
RMON delivers information in RMON groups of monitoring elements, each providing specific sets of data to meet common network-monitoring requirements. Each group is optional so that you do not need to support all the groups within the Management Information Base (MIB). Some RMON groups require support of other RMON groups to function properly.
The RMON Alarm group periodically takes statistical samples from variables in a probe and compares them with previously configured thresholds. If the monitored variable crosses a threshold, an event is generated. The RMON Alarm group provides information on the alarm type, the interval, and the start and stop thresholds.
The RMON Events group controls the generation and notification of events from a device. The RMON Events group provides information on the event type, the event description, and the time that the event was sent.
RMON delivers information in RMON groups of monitoring elements, each providing specific sets of data to meet common network-monitoring requirements. Each group is optional so that you do not need to support all the groups within the Management Information Base (MIB). Some RMON groups require support of other RMON groups to function properly.
The table below summarizes the nine monitoring groups specified in the RFC 1757 Ethernet RMON MIB. For more information on gathering RMON statistics for these data types, refer to Configuring RMON Groups.
Note |
All Cisco IOS software images ordered without the explicit RMON option include limited RMON support (RMON alarms and event groups only). Images ordered with the RMON option include support for all nine management groups (statistics, history, alarms, hosts, hostTopN, matrix, filter, capture, and event). As a security precaution, support for the capture group allows capture of packet header information only; data payloads are not captured. |
Table 1 | RMON Monitoring Groups |
RMON Group |
Function |
Elements |
---|---|---|
Statistics |
Contains statistics measured by the probe for each monitored interface on this device. |
Packets dropped, packets sent, bytes sent (octets), broadcast packets, multicast packets, CRC errors, runts, giants, fragments, jabbers, collisions, and counters for packets ranging from 64 to 128, 128 to 256, 256 to 512, 512 to 1024, and 1024 to 1518 bytes. |
History |
Records periodic statistical samples from a network and stores them for later retrieval. |
Sample period, number of samples, items sampled. |
Alarm |
Periodically takes statistical samples from variables in the probe and compares them with previously configured thresholds. If the monitored variable crosses a threshold, an event is generated. |
Includes the alarm table and requires the implementation of the event group. Alarm type, interval, starting threshold, stop threshold. |
Host |
Contains statistics associated with each host discovered on the network. |
Host address, packets, and bytes received and transmitted, as well as broadcast, multicast, and error packets. |
HostTopN |
Prepares tables that describe the hosts that top a list ordered by one of their base statistics over an interval specified by the management station. Thus, these statistics are rate-based. |
Statistics, host(s), sample start and stop periods, rate base, duration. |
Matrix |
Stores statistics for conversations between sets of two addresses. As the device detects a new conversation, it creates a new entry in its table. |
Source and destination address pairs and packets, bytes, and errors for each pair. |
Filters |
Enables packets to be matched by a filter equation. These matched packets form a data stream that might be captured or that might generate events. |
Bit-filter type (mask or not mask), filter expression (bit level), conditional expression (and, or not) to other filters. |
Packet Capture |
Enables packets to be captured after they flow through a channel. |
Size of buffer for captured packets, full status (alarm), number of captured packets. |
Events |
Controls the generation and notification of events from this device. |
Event type, description, last time event sent. |
RMON allows various network agents and console systems to exchange network monitoring data. Thresholds allow you to minimize the number of notifications sent on the network. The RMON MIB defines two traps, the risingAlarm trap which is the rising-threshold value and fallingAlarm trap which is the falling-threshold value. Alarms are triggered when a problem exceeds a set rising-threshold value. No alarm notifications are sent until the network agent recovers, as defined by the falling-threshold value. This means that notifications are not sent each time a minor failure or recovery occurs.
You can set an RMON alarm on any MIB object in the access server. You cannot disable all the alarms you configure at the same time. The delta value tests the change between MIB variables, which affects the alarmSampleType in the alarmTable of the RMON MIB. The absolute value tests each MIB variable directly, which affects the alarmSampleType in the alarmTable of the RMON MIB.
Refer to RFC 1757 to learn more about alarms and events and how they interact with each other.
RMON MIB supports for polling of 64 bit counters and includes the following features:
Table 2 | partial probeConfig Group Objects |
Object |
Description |
---|---|
probeCapabilities |
The RMON software groups implemented. |
probeSoftwareRev |
The current version of Cisco IOS software running on the device. |
probeHardwareRev |
The current version of the Cisco device. |
probeDateTime |
The current date and time. |
probeResetControl |
Initiates a reset. |
probeDownloadFile |
The source of the image running on the device. |
probeDownloadTFTPServer |
The address of the server that contains the Trivial File Transfer Protocol (TFTP) file that is used by the device to download new versions of Cisco IOS software. |
probeDownloadAction |
Specifies the action of the commands that cause the device to reboot. |
probeDownloadStatus |
The state of a reboot. |
netDefaultGateway |
The router mapped to the device as the default gateway. |
hcRMONCapabilities |
Specifies the features mapped to this version of RMON. |
In Cisco IOS Release 12.1, the RMON agent was rewritten to improve performance and add some new features. The table below highlights some of the improvements implemented.
Table 3 | RMON MIB Updates |
Prior to the RMON MIB Update in Cisco IOS Release 12.1 |
New Functionality in Cisco IOS Release 12.1 |
---|---|
RMON configurations do not persist across reboots. Information is lost after a new session on the RMON server. |
RMON configurations persist across reboots. Information is preserved after a new session on the RMON server. |
Packet analysis applies only on the MAC header of the packet. |
Complete packet capture is performed with analysis applied to all frames in packet. |
Only RMON I MIB objects are used for network monitoring. |
RMON I and selected RMON II objects are used for network monitoring. |
The High Capacity (HC) Alarm MIB (HC-ALARM-MIB) provides the capability to create alarms that monitor thresholds crossed by 64-bit MIB objects on an access server. The Remote Monitoring (RMON)-1 Alarm group and RMON-1 notification types are specific to 32-bit objects. The HC alarm MIB supports the polling of 64-bit RMON objects and is an extension of the RMON-1 Alarm group.
The RMON-1 Events group controls the generation and notification of events from a device. When an event is created, it is added to the RMON-1 Events group table. Each entry in this table describes parameters of an event that can be triggered by alarms. An entry may specify that a log entry must be created whenever an event occurs. The entry may also specify that a notification should occur through Simple Network Management Protocol (SNMP) trap messages.
The HC Alarm MIB defines two SNMP traps: hcRisingAlarm and hcFallingAlarm. The hcRisingAlarm trap is used when a rising-threshold value is crossed, and the hcFallingAlarm trap is used when a falling-threshold value is crossed.
High Capacity (HC) alarms are triggered when a monitored variable exceeds a set rising-threshold value or falls below a set falling-threshold value. HC alarms can be set on any HC MIB object on an access server.
Given below is a typical flow of how a 64-bit RMON object is monitored:
This task explains how to configure RMON and RMON queue size. In native mode, RMON monitors only those packets that are received by the interface. In promiscuous mode, RMON monitors all packets on the LAN segment.
The following tasks explain how to configure RMON groups by gathering RMON statistics for data types.
The following example shows how to configure RMON with a queuesize of 100 packets in promiscuous mode:
Device> enable Device# configure terminal Device(config)# interface fastethernet 0/0 Device(config-if)# rmon promiscuous Device(config-if)# exit Device(config)# rmon queuesize 100
The following is a sample output from the show rmon command. All counters are from the time the device was initialized.
Device# show rmon
145678 packets input (34562 promiscuous), 0 drops
145678 packets processed, 0 on queue, queue utilization 15/100
The following example shows how to enable the rmon event global configuration command:
Device> enable Device# configure terminal Device(config)# rmon event 1 log trap eventtrap description "High ifOutErrors" owner ownerA
The following example shows how to create RMON event number 1, which is defined as High ifOutErrors, and generates a log entry when the event is triggered by an alarm. The user ownerA owns the row that is created in the event table by this command. This example also shows how to generate a Simple Network Management Protocol (SNMP) trap when the event is triggered.
The following is a sample output from the show rmon events command:
Device# show rmon events
Event 1 is active, owned by ownerA
Description is High ifOutErrors
Event firing causes log and trap to community rmonTrap, last fired 00:00:00
The following example shows how to configure an RMON alarm using the rmon alarm global configuration command:
Device> enable Device# configure terminal Device(config)# rmon alarm 10 ifEntry.20.1 20 delta rising-threshold 15 1 falling-threshold 0 owner ownerA
The following example shows how to configure RMON alarm number 10. The alarm monitors the MIB variable ifEntry.20.1 once every 20 seconds until the alarm is disabled, and checks the change in the rise or fall of the variable. If the ifEntry.20.1 value shows a MIB counter increase of 15 or more, such as from 100000 to 100015, the alarm is triggered. The alarm in turn triggers event number 1, which is configured with the rmon event command. Possible events include a log entry or an SNMP trap. If the ifEntry.20.1 value changes by 0, the alarm is reset and can be triggered again.
The following is sample output from the show rmon alarms command
Device# show rmon alarms
Alarm 2 is active, owned by owner_a
Monitors ifEntry.20.1.20 every 20 seconds
Taking delta samples, last value was 0
Rising threshold is 15, assigned to event 12
Falling threshold is 0, assigned to event 0
On startup enable rising or falling alarm
The following example shows how to configure an RMON HC alarm using the rmon hc-alarms global configuration command:
Device> enable Device# configure terminal Device(config)# rmon hc-alarms 2 ifInOctets.2 20 delta rising-threshold 2000 2 falling-threshold 1000 1 owner own
The following example shows how to configure RMON HC alarm number 2. The alarm monitors the MIB variable ifInOctets.2 once every 20 seconds until the alarm is disabled, and checks the change in the rise or fall of the variable. If the ifInOctets.2value shows a MIB counter increase of 2000 or more, such as from 100000 to 103000, the alarm is triggered. The alarm in turn triggers event number 2, which is configured with the rmon event command. Possible events include a log entry or a Simple Network Management Protocol (SNMP) trap. If theifInOctets.2 value changes by 1000 (falling threshold is 1000), the alarm is reset and can be triggered again.
To display the contents of the RMON HC alarm table of the device, use the show rmon hc-alarms command in privileged EXEC mode. The following is a sample output from the command:
Device# show rmon hc-alarms
Monitors ifInOctets.1 every 20 second(s)
Taking absolute samples, last value was 0
Rising threshold Low is 4096, Rising threshold Hi is 0,
assigned to event 0
Falling threshold Low is 1280, Falling threshold Hi is 0,
assigned to event 0
On startup enable rising or falling alarm
The following example shows how to enable the RMON collection matrix group of statistics with an ID number of 25 and specifies john as the owner:
Router> enable Router# configure terminal Router(config)# interface fastethernet 0/0 Router(config-if)# rmon collection matrix controlEntry 25 owner john
To view values associated with RMON variables, enter the show rmon matrix privileged EXEC command (Cisco 2500 series routers and Cisco AS5200 access servers only). The following is a sample output:
Router# show rmon matrix
Matrix 1 is active and owned by john
Monitors controlEntry
Table size is 25, last time an entry was deleted was at 11:18:09
Source addr is 0000.0c47.007b, dest addr is ffff.ffff.ffff
Transmitted 2 pkts, 128 octets, 0 errors
Source addr is 0000.92a8.319e, dest addr is 0060.5c86.5b82
Transmitted 2 pkts, 384 octets, 1 error
Related Topic |
Document Title |
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Cisco IOS commands |
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CNS commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples |
MIB |
MIBs Link |
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To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description |
Link |
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 4 | Feature Information for Configuring RMON Support |
Feature Name |
Releases |
Feature Information |
---|---|---|
RMON Events and Alarms |
Cisco IOS XE Release 2.1 |
The RMON Events and Alarms feature introduces the ability to combine RMON alarms and events (classes of messages that indicate traffic violations and various unusual occurrences over a network) with existing MIBs allows you to choose where proactive monitoring will occur. The following commands were introduced or modified: rmon alarm and rmon event. |
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