Configuring RMON Support
This module describes the Remote Monitoring (RMON) MIB agent specification and its usage in conjunction with Simple Network Management Protocol (SNMP) to monitor traffic using alarms and events.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 document.
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.
Prerequisites for Configuring RMON Support
- RMON requires SNMP to be configured (you must be running a version of SNMP on the server that contains the RMON MIB).
- RMON can be very data and processor intensive. You must measure usage effects to ensure that router performance is not degraded by RMON and to minimize excessive management traffic overhead. Native mode in RMON is less intensive than promiscuous mode.
Restrictions for Configuring RMON Support
- Full RMON packet analysis (as described in RFC 1757) is supported only on an Ethernet interface of Cisco 2500 series routers and Cisco AS5200 series universal access servers.
- A generic RMON console application is recommended in order to take advantage of the RMON network management capabilities.
Information About Configuring RMON Support
RMON Overview
RMON is a standard monitoring specification that enables various network monitors and console systems to exchange network-monitoring data. RMON provides network administrators with more flexibility in selecting network-monitoring probes and consoles with features that meet their particular networking needs.
The RMON specification defines a set of statistics and functions that can be exchanged between RMON-compliant console managers and network probes. RMON provides network administrators with comprehensive network-fault diagnosis, planning, and performance-tuning information.
The RMON feature identifies activity on individual nodes and allows you to monitor all nodes and their interaction on a LAN segment. Used in conjunction with the SNMP agent in a router, RMON allows you to view both traffic that flows through the router and segment traffic that is not necessarily destined for the router. Combining 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.
RMON Groups
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 Event and Alarm Notifications
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 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 once. 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
RMON MIB supports for polling of 64 bit counters and includes the following features:
- usrHistory group. This MIB group is similar to the RMON etherHistory group except that the group enables you to specify the MIB objects that are collected at each interval.
- partial probeConfig group. This MIB group is a subset of the probeConfig group implemented in read-only mode. These objects implement the simple scalars from this group. The table below details new partial probeConfig group objects.
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. |
HC Alarm MIB
The high-capacity (HC) Alarm MIB, which is an extension of RMON Alarm group table objects, supports polling of RMON variables up to 64 bit values. The HC-ALARM-MIB defines two traps, the hcRisingAlarm which provides the rising-threshold value and hcFallingAlarm which provides the falling-threshold value.
Refer to RFC 3434 to learn more about HC alarms.
How to Configure RMON Support
Configuring RMON
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.
DETAILED STEPS
Configuring RMON Event and Alarm Notifications
The following tasks describe how to configure RMON event and alarm notifications.
DETAILED STEPS
Configuring RMON Groups
The following tasks explain how to configure RMON groups by gathering RMON statistics for data types.
DETAILED STEPS
Configuration Examples for RMON Support
- Configuring RMON Example
- Configuring RMON Event and Alarm Notifications Example
- Configuring RMON Tables Example
Configuring RMON Example
The following example shows how to configure RMON with a queuesize of 100 packets in promiscuous mode:
Router> enable Router# configure terminal Router(config)# interface fastethernet 0/0 Router(config-if)# rmon promiscuous Router(config-if)# exit Router(config)# rmon queuesize 100
The following is a sample output from the show rmon command. All counters are from the time the router was initialized:
Router# show rmon
145678 packets input (34562 promiscuous), 0 drops
145678 packets processed, 0 on queue, queue utilization 15/100
Configuring RMON Event and Alarm Notifications Example
The following example shows how to enable the rmon eventglobal configurationcommand:
Router> enable Router# configure terminal Router(config)# rmon event 1 log trap eventtrap description “High ifOutErrors” owner ownerA
This example creates 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 generates an SNMP trap when the event is triggered.
The following is a sample output from the show rmon events command:
Router# 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:
Router> enable Router# configure terminal Router(config)# rmon alarm 10 ifEntry.20.1 20 delta rising-threshold 15 1 falling-threshold 0 owner ownerA
This example configures 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
Router# 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:
Router> enable Router# configure terminal Router(config)# rmon hc-alarms 2 ifInOctets.2 20 delta rising-threshold 2000 2 falling-threshold 1000 1 owner own
This example configures 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 router, use the show rmon hc-alarms command in privileged EXEC mode. The following is sample output:
Router# show rmon hc-alarms
Router#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
Configuring RMON Tables Example
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
Additional References
Related Documents
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
CNS commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples |
Cisco IOS Network Management Command Reference 3.0 |
Standards
Standard |
Title |
---|---|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
MIBs
MIB |
MIBs Link |
---|---|
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
RFC |
Title |
---|---|
RFC 1757 |
Remote Network Monitoring Management Information Base |
RFC 2021 |
Remote Network Monitoring Management Information Base Version 2 using SMIv2 |
RFC 3434 |
Remote Monitoring MIB Extensions for High Capacity Alarms |
Technical Assistance
Description |
Link |
---|---|
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. |
Feature Information for Configuring RMON Support
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 |
---|---|---|
HC Alarm MIB |
12.2(33)SXI 12.2(33)SRE |
The HC Alarm MIB feature provides an extension to the RMON-1 Alarm group table objects which was used to support counter 32 objects for threshold capabilities. The HC Alarm MIB adds support to threshold capabilities for counter 64 objects. The following commands were introduced: rmon hc-alarms, show rmon hc-alarms. |
Remote Monitoring MIB Update |
12.0(5)T |
The RMON Rewrite feature updated the Remote Monitoring MIB to improve performance and available features. The following commands were introduced: rmon capture-userdata, rmon collection history, rmon collection host, rmon collection matrix, rmon collection rmon1, show rmon capture, show rmon filter, show rmon hosts, show rmon matrix. |
RMON Events and Alarms |
11.2 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. In Cisco IOS XE Release 2.1, this feature was introduced on Cisco ASR 1000 series routers. The following commands were introduced: rmon alarm, rmon event, rmon queuesize. |
RMON Full |
11.2 |
The RMON Full feature identifies activity on individual nodes and helps monitor all nodes and their interaction on a LAN segment. Used in conjunction with the SNMP agent in a router, RMON can be used to view both traffic that flows through the router and segment traffic not necessarily destined for the router. |
RMON MIB enhancement to support 64 bit counters |
12.2(33)SXI 12.2(33)SRE |
RMON MIB enhancement to support 64 bit counters features provides support for the ability to poll 64 bit counters. |
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