Table Of Contents
Prerequisites for SNMP for Stateful Switchover
Restrictions for SNMP for Stateful Switchover
Information About SNMP for Stateful Switchover
SNMP for Stateful Switchover Overview
Uninterrupted Service Using SSO
SNMP Configuration MIBs for SSO Support
Infrastructure MIBs for SSO Support
CISCO-RF-MIB Modifications for SSO Support
New cRFHistorySwitchOverTable Table in CISCO-RF-MIB for SSO Support
New Objects in CISCO-RF-MIB for SSO Support
SNMP Network Management for SSO Benefits
How to Configure SNMP for Stateful Switchover
Troubleshooting SNMP for Stateful Switchover
Configuration Examples for SNMP for Stateful Switchover
Feature Information for SNMP for Stateful Switchover
SNMP for Stateful Switchover
First Published: July 22, 2002Last Updated: March 2, 2009This document describes the enhancements and modifications made to the Cisco Simple Network Management Protocol (SNMP) infrastructure to support SSO for Route Processors (RPs).
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 for SNMP for Stateful Switchover" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for SNMP for Stateful Switchover
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Prerequisites for SNMP for Stateful Switchover
The router must be in SSO mode.
Restrictions for SNMP for Stateful Switchover
Counter and Statistics
Statistics and counter values will not be synchronized from the active to the standby RP.
MIB Limitations
No MIBs other than the ones mentioned in the "MIB Support" section are synchronized between the active and the standby RPs.
Possible Failure of SNMP Requests
SNMP requests might fail during the switchover process, that is, while the standby RP is taking over as the active RP. Data in the unsynchronized MIBs may be out of synchronization, and the information in these MIBs might be lost on a switchover.
Information About SNMP for Stateful Switchover
To use SNMP for stateful switchover, you need to understand the following concepts:
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SNMP for Stateful Switchover Overview
The SNMP and stateful switchover feature helps to improve the availability of networks made up of Cisco IOS XE-based networking devices. Using SSO, a networking device with redundant RPs will continue forwarding traffic, continue operating as a routing protocol peer, and remain manageable under a set of circumstances that ordinarily would cause an interruption in service.
The SSO feature allows one of the processors on the networking device to operate as the active RP, which passes the necessary system, routing, and application state information to the standby RP. Upon switchover, the standby RP quickly assumes the role of active RP. The goal of SNMP network management with SSO functionality is to provide an uninterrupted management interface to the end user during and after a switchover. For more information about the SSO feature, see the "Stateful Switchover" chapter in the Cisco IOS XE High Availability Configuration Guide.
Network Management for SSO
Network management support for SSO is provided through the synchronization of specific SNMP data between the active and standby RPs. From a network management perspective, this synchronization helps to provide an uninterrupted management interface to the network administrator.
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Network management services for SSO address a number of issues, which are described in the following sections:
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Uninterrupted Service Using SSO
When a networking device uses SSO, the network management engine of the standby RP should be indistinguishable from the network management engine of the active RP. A network management system (NMS) should not interpret a switchover to mean that a new device has come up.
The sysUpTime MIB object reports the system uptime. To prevent a switchover from being flagged as a restart, this object is synchronized between the active and the standby RPs. As a result, no coldStart or warmStart traps will be generated as a result of the switchover—the ciscoRFSwactNotif notification is used to signal a switchover.
Communication with the NMS
The following sections describe concepts about communication with the NMS:
Counters and Statistics
The various counters and statistics maintained in the RP are not synchronized because they may change often and the degree of synchronization they require is substantial. They also are not critical to the system operation. Because of this lack of synchronization, counter objects experience a discontinuity after a switchover. The cRFStatusFailoverTime will be the value of sysUpTime when any one or more of the counters experiences a discontinuity.
Switchover Notification
The ciscoRFSwactNotif notification informs the NMS about a switchover. This notification provides information regarding the unit ID of the originator of the notification, the newly active redundant unit, the sysUptime data, and reason codes for why a switchover has occurred. The NMS can then use the ciscoRFSwactNotif notification to resynchronize the counter statistics values, if necessary. For more information, see the "CISCO-RF-MIB Modifications for SSO Support" section.
Traps
Only notifications generated on the active RP are sent to the notification destination. None of the notifications generated on the standby RP are sent to the notification destination. Furthermore, notifications might be lost if they were generated on the active RP before a switchover. The NMS should be aware of these constraints.
SSO MIB Support
This section describes the level of synchronization supported by the MIBs listed in the following sections. MIBs that are not listed in this section do not synchronize data between the redundant units. MIB synchronization for SSO only occurs when the system is in SSO mode.
SSO MIB support has three parts:
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SNMP Configuration MIBs for SSO Support
All the objects in the following MIBs that contain SNMP configuration data are synchronized between the active and standby RPs:
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Core MIBs for SSO Support
Core MIBs are as follows:
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Infrastructure MIBs for SSO Support
Infrastructure MIBs are as follows:
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CISCO-RF-MIB Modifications for SSO Support
The CISCO-RF-MIB provides configuration control and status for the redundancy facility (RF) subsystem. The CISCO-RF-MIB has been modified to support SSO functionality. A new cRFHistory subgroup has been added in this release. The subgroup consists of one table (cRFHistorySwitchOverTable) and three objects (cRFHistoryTableMaxLength, cRFHistoryColdStarts, and cRFHistoryStandbyAvailTime) described in the following sections:
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New cRFHistorySwitchOverTable Table in CISCO-RF-MIB for SSO Support
The cRFHistorySwitchOverTable tracks the history of switchovers that have occurred since system initialization. New objects that have been added as part of this table are as follows:
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New Objects in CISCO-RF-MIB for SSO Support
The object added to the new cRFHistory subgroup are as follows:
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Two objects related to switchover status have also been added:
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SNMP Network Management for SSO Benefits
SNMP network management with SSO functionality ensures an uninterrupted management interface to the end user. The network administrator can differentiate a switchover from a system restart based on the notification type (for example, ciscoRFSwactNotif for switchover and coldStart or warmStart for system restarts). Uninterrupted service also includes synchronizing the SNMP configuration and data from core MIBs such as IF-MIB and ENTITY-MIB to the standby RP.
How to Configure SNMP for Stateful Switchover
To configure the router to run in SSO mode and to verify that the router is running in SSO mode, see the "Stateful Switchover" chapter in the Cisco IOS XE High Availability Configuration Guide and the Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide.
For further information on configuring SNMP support, see the "Configuring SNMP Support" chapter in the Cisco IOS XE Network Management Configuration Guide.
This section contains the following task:
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Troubleshooting SNMP for Stateful Switchover
Perform the following task to troubleshoot SNMP for SSO.
SUMMARY STEPS
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DETAILED STEPS
Configuration Examples for SNMP for Stateful Switchover
For SSO configuration examples, see the "Stateful Switchover" chapter in the Cisco IOS XE High Availability Configuration Guide and the Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide.
For SNMP configuration examples, see the "Configuring SNMP Support" chapter in the Cisco IOS XE Network Management Configuration Guide.
Additional References
The following sections provide references related to the SNMP for Stateful Switchover feature.
Related Documents
Stateful switchover
"Stateful Switchover" chapter in the Cisco IOS XE High Availability Configuration Guide
SNMP configuration task
"Configuring SNMP Support" chapter of Cisco IOS XE Network Management Configuration Guide
SNMP commands
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
Technical Assistance
Feature Information for SNMP for Stateful Switchover
Table 1 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE Software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
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