Table Of Contents
Cisco Express Forwarding—SNMP CEF-MIB Support
Prerequisites for Cisco Express Forwarding—SNMP CEF-MIB Support
Restrictions for Cisco Express Forwarding—SNMP CEF-MIB Support
Information About Cisco Express Forwarding—SNMP CEF-MIB Support
Cisco Express Forwarding Functional Overview
CEF Information Managed by the CISCO-CEF-MIB
CISCO-CEF-MIB Object Groups and Related Tables
Brief Description of the Tables in the CISCO-CEF-MIB
CEF Configuration and Monitoring Operations Available Through the CISCO-CEF-MIB
How to Configure Cisco Express Forwarding—SNMP CEF-MIB Support
Configuring the Router to Use SNMP
Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications
Configuring SNMP Notifications for Cisco Express Forwarding Events
Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notification
Configuration Examples for Cisco Express Forwarding—SNMP CEF-MIB Support
Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications: Example
Configuring SNMP Notifications for Cisco Express Forwarding Events: Example
Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications: Example
snmp mib cef throttling-interval
Feature Information for Cisco Express Forwarding—SNMP CEF-MIB Support
Cisco Express Forwarding—SNMP CEF-MIB Support
First Published: December 4, 2006Last Updated: December 4, 2006The Cisco Express Forwarding—SNMP CEF-MIB Support feature introduces the CISCO-CEF-MIB that allows management applications through the use of the Simple Network Management Protocol (SNMP) to configure and monitor Cisco Express Forwarding (CEF) operational data and to provide notification when CEF encounters specific configured events. This module describes how to use the CISCO-CEF-MIB to manage and monitor objects related to CEF operation.
CEF is an advanced Layer 3 IP switching technology. It optimizes network performance and scalability for all kinds of networks: those that carry small amounts of traffic and those that carry large amounts of traffic in complex patterns, such as the Internet and networks characterized by intensive web-based applications or interactive sessions.
Finding Feature Information in This Module
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Contents
•Prerequisites for Cisco Express Forwarding—SNMP CEF-MIB Support
•Restrictions for Cisco Express Forwarding—SNMP CEF-MIB Support
•Information About Cisco Express Forwarding—SNMP CEF-MIB Support
•How to Configure Cisco Express Forwarding—SNMP CEF-MIB Support
•Configuration Examples for Cisco Express Forwarding—SNMP CEF-MIB Support
•Feature Information for Cisco Express Forwarding—SNMP CEF-MIB Support
Prerequisites for Cisco Express Forwarding—SNMP CEF-MIB Support
The Cisco Express Forwarding—SNMP CEF-MIB Support feature has the following prerequisites:
•CEF or distributed CEF (dCEF) must be configured on your system.
•The Cisco Express Forwarding infrastructure introduced in Cisco IOS Release12.2(22)S must be included in the image on your system.
•The router on which the Cisco Express Forwarding—SNMP CEF-MIB Support features is to be used should be configured for SNMP access. Refer to the "Configuring the Router to Use SNMP" section in this document for more information.
Restrictions for Cisco Express Forwarding—SNMP CEF-MIB Support
The CISCO-CEF-MIB prefix database and its related database can be very large. Therefore, walking the prefix table could take a considerable amount of time.
Information About Cisco Express Forwarding—SNMP CEF-MIB Support
To configure SNMP and the CISCO-CEF-MIB to monitor CEF data and events, you should understand the following concepts:
•Cisco Express Forwarding Functional Overview
•CEF Information Managed by the CISCO-CEF-MIB
•CISCO-CEF-MIB Object Groups and Related Tables
•Brief Description of the Tables in the CISCO-CEF-MIB
•CEF Configuration and Monitoring Operations Available Through the CISCO-CEF-MIB
Cisco Express Forwarding Functional Overview
CEF is an advanced Layer 3 IP switching technology. It uses a Forwarding Information Base (FIB) to make IP destination prefix-based switching decisions. The FIB is conceptually similar to a routing table or information base. It maintains the forwarding information contained in the IP routing table. When routing or topology changes occur in the network, the IP routing table is updated, and those changes are propagated to the FIB. The FIB maintains next-hop address information based on the information in the IP routing table. The two main components of CEF operation are the FIB and Adjacency tables.
CEF uses adjacency tables to prepend Layer 2 addressing information. The adjacency table maintains Layer 2 next-hop addresses for all FIB entries. Nodes in the network are said to be adjacent if they can reach each other with a single hop across a link layer. CEF discovers and solves adjacencies and populates the adjacency tables.
CISCO-CEF-MIB Benefits
Command-line interface (CLI) show commands are available to obtain CEF operational information. Managing CEF using the CLI can be a time consuming task. The increasing capacity of Cisco routers makes parsing through the show commands output to obtain the needed CEF operational parameters more and more difficult.
In Cisco IOS Release 12.2(31)SB and later releases, the CISCO-CEF-MIB allows you to manage and monitor the CEF operation using SNMP. In addition, you can configure SNMP to notify you if CEF encounters errors.
With the CISCO-CEF-MIB introduced with the Cisco Express Forwarding—SNMP CEF-MIB Support feature, you can access in real time operational information stored in the FIB and adjacency tables, switching statistics, information on resource failures, and configure parameters related to CEF features by utilizing a MIB implementation based on SNMP. This information is accessed using get and set commands entered on the network management system (NMS) workstation or host system for which SNMP has been implemented. The NMS workstation is also known as the SNMP manager.
CEF is available in all Cisco routers. However, CISCO-CEF-MIB support of CEF management is dependent on the new infrastructure introduced in Cisco IOS Release 12.2(22)S.
The implementation of the CISCO-CEF-MIB in Cisco IOS Release 12.2(31)SB2 manages CEF instances running on the Route Processor (RP). Information about CEF running on the line cards is available to the RP about CEF peers only.
The CISCO-CEF-MIB supports configuration and monitoring for both IP Versions, IP Version 4 (IPv4) and Version 6 (IPv6).
CEF Information Managed by the CISCO-CEF-MIB
SNMP has historically been used to collect network information. SNMP permits retrieval of critical information from network elements such as routers, switches, and workstations.
The CISCO-CEF-MIB provides managed objects that enable a network administrator to monitor the following:
•CEF administrative and operational states as displayed in the output of the show ip cef summary command
•Notifications for CEF events: CEF state changes, CEF failures (with a predefined reason), and Route Processor (RP) and line card inconsistencies.
•CEF-related parameters for the associated interface as displayed by the show cef interface command)
•Line card CEF states and line card CEF FIB states in the Linecard table as displayed by the show cef linecard command
•CEF statistics: switching statistics, punt and punt-to-host counters as displayed by the show ip cef switching stats command, and per-prefix counters and nonrecursive counters
•Notification for both IPv4 and IPv6, when CEF is switched between disable and enable and between CEF and distributed CEF
The SNMP CISCO-CEF-MIB provides managed objects that enable a network administrator to configure the following:
•CEF and dCEF administration status:
•CEF accounting-related parameters
•CEF load sharing-related parameters
•Traffic-related configuration parameters
CISCO-CEF-MIB Object Groups and Related Tables
The SNMP CISCO-CEF-MIB allows the configuration and management of CEF related objects. The MIB contains the following object groups:
•CEF FIB group
•CEF Adjacency group
•CEF Forwarding Element group
•CEF Cfg group
•CEF Interface group
•CEF Peer group
•CEF Consistency (CC) group
•CEF State Group
•CEF Notification Control group
In the CISCO-CEF-MIB, configuration objects are defined as read-write and the other objects are defined as read-only.
The CISCO-CEF-MIB contains tables related to the CEF object groups. These tables provide information about prefixes, forwarding paths, adjacencies, output chain elements (OCEs), prefix-based statistics, information about CEF configuration, consistency checkers, switching statistics, and line card-specific managed objects.
The CISCO-CEF-MIB also defines CEF notifications that you can enable or disable through the MIB or CLI commands.
The index for most tables in the CISCO-CEF-MIB is entPhysicalIndex.
Brief Description of the Tables in the CISCO-CEF-MIB
Following is a list and a brief description of the tables provided by the CISCO-CEF-MIB:
•The CEF FIB Summary table (cefFIBSummaryTable) contains the number of forwarding prefixes for both IPv4 and IPv6 protocols; a summary of the CEF Forwarding table.
•The CEF Forwarding table (cefPrefixTable) lists all the prefixes and related counters. It also contains a pointer to the Forwarding Element Selection table.
•The CEF Longest Match Prefix table (cefLMPrefixTable) returns the longest prefix match for the given destination address. An optional cefLMPrefixSpinLock object is provided to reduce conflict in instances when more than one application acts on the CEF Longest Match Prefix table.
•The CEF Path table (cefPathTable) lists all the Cisco Express Forwarding paths.
•The CEF Adjacency Summary table (cefAdJSummaryTable) contains the total number of complete, incomplete, fixup, and redirect adjacencies for all link types.
•The CEF Adjacency table (cefAdjTable) lists all the adjacencies. It contains the adjacency source, encapsulation string, fixup, and Layer 3 maximum transmission unit (MTU) associated with the adjacency entry. It contains a pointer to the forwarding element selection table (if the adjacency is a MID chain adjacency).
•The CEF Forwarding Element Selection table (cefFESelectionTable) represents the OCE chains in flattened format. This table shows only the labels, table ID, and adjacency traversed in the OCE chain. It also contains the weight associated with each OCE chain.
•CEF Cfg table (cefCfgTable) contains all the global configuration parameters related to CEF: administration and operational status, accounting-related configuration parameters, load-sharing algorithms and IDs, and traffic statistics parameters.
•CEF Interface table (cefIntTable) contains the interface specific CEF parameter: interface switching state, interface load sharing (per packet and per destination), and interface nonrecursive routing (internal and external).
•CEF Peer table or Linecard table (cefPeerTable) contains CEF information related to peers on a managed line card: line card operational state and the number of time the line card session resets.
•CEF Peer FIB table (cefPeerFIBTable) contains information about the operational state of the Forwarding Information Bases (FIBs) on each line card.
•The CEF Prefix Length Statistics table (cefStatsPrefixTable) maintains prefix length-based statistics.
•CEF Switching Stats table (cefSwitchingStatsTable) contains the switching statistics for each switching path: drop counters, punt counters, and punt-to-host counters.
•CEF IP Prefix Consistency Checker Global group (cefCCGlobalTable) contains all global configuration parameter for the consistency checkers: auto repair, enable and disable, delay, and hold down; enable or disable the passive consistency checkers; enable or disable the error messages for consistency detection; and the mechanism to activate the full scan consistency checkers. This table also displays the state of full scan consistency checkers.
•CEF Consistency Checker Type table (cefCCTypeTable) contains the consistency checker type specific parameters: frequency and count of scan for passive scanners and the queries sent, ignored, checked, and iterated.
•CEF Inconsistency Record table (cefInconsistencyRecordTable) contains the detected inconsistency records: prefix address and length, table ID, consistency checker type, slot ID, and the reason for the inconsistency (missing or checksum error).
See "CEF Configuration and Monitoring Operations Available Through the CISCO-CEF-MIB" section for information about the specific objects available through the CISCO-CEF-MIB tables.
Figure 1 shows the contents of the CISCO-CEF-MIB core tables and the relationships of the tables to one another.
Figure 1 CISCO-CEF-MIB Main Tables, Table Contents, and Relationships
CEF Configuration and Monitoring Operations Available Through the CISCO-CEF-MIB
You can use SNMP get and set commands to configure and monitor CEF operations that are available through the CISCO-CEF-MIB tables. This section describes the configuration and monitoring operations for each table.
Table 1 lists the CEF monitoring operations and associated MIB objects provided by the CEF FIB Summary table (cefFIBSummaryTable).
Table 1 CEF FIB Summary Table—CEF Operation and Associated MIB Object
CEF Operation DescriptionGets the number of forwarding prefixes for IPv4 and IPv6
cefFIBSummaryFwdPrefixes
Table 2 lists the CEF monitoring operations and associated MIB objects provided by the CEF Forwarding table (cefPrefixTable).
Table 3 lists the CEF monitoring operations and associated MIB objects provided by the CEF Longest Match Prefix table (cefLMPrefixTable).
Table 4 lists the CEF monitoring operations and associated MIB objects provided by the CEF Path table (cefPathTable).
Table 5 lists the CEF monitoring operations and associated MIB objects provided by the CEF Adjacency Summary table (cefAdjSummaryTable).
Table 6 lists the CEF monitoring operations and associated MIB objects provided by the Adjacency table (cefAdjTable).
Table 7 lists the CEF monitoring operations and associated MIB objects provided by the CEF Forwarding Element Selection table (cefFESelectionTable).
Table 8 lists the CEF configuration and monitoring operations and associated MIB objects provided by the CEF Cfg table (cefCfgTable).
Table 9 lists the CEF monitoring operations and associated MIB objects provided by the CEF Resource table (cefResourceTable).
Table 10 lists the CEF configuration and monitoring operations and associated MIB objects provided by the CEF Interface table (cefIntTable).
Table 11 lists the CEF monitoring operations and associated MIB objects provided by the CEF Peer table (or Linecard table) (cefPeerTable).
Table 12 lists the CEF monitoring operation and associated MIB object provided by the CEF Peer FIB table (cefPeerFIBTable).
Table 12 CEF Peer FIB Table—CEF Operation and Associate MIB Object
CEF Operation MIB ObjectsGets the current CEF FIB operation state of the peer entity
cefPeerFIBOperState
Table 13 lists the CEF monitoring operations and associated MIB objects provided by the CEF Prefix length Statistics table (cefStatsPrefixTable).
Table 14 lists the CEF monitoring operations and associated MIB objects provided by the CEF Switching Statistics table (cefSwitchingStatsTable).
Table 15 lists the CEF configuration and monitoring operations and associated MIB objects provided by the CEF IP Prefix Consistency Checker group (cefCCGlobalTable).
Table 16 lists the CEF configuration and monitoring operations and associated MIB objects provided by the CEF Consistency Checker Type table (cefCCTypeTable).
Table 17 lists the CEF configuration and monitoring operations and associated MIB objects provided by the CEF Inconsistency Record table (cefInconsistencyRecordTable).
CISCO-CEF-MIB Notifications
Table 18 lists the CEF operations associated with the CISCO-CEF-MIB objects that enable the sending of CEF notifications.
You can enable or disable these notifications through the MIB or by entering a CLI command. Table 19 contains a description of the notifications and the commands you use to enable each notification.
Note You must enter a snmp-server host command before you enter a command to enable or disable a CISCO-CEF-MIB notification.
How to Configure Cisco Express Forwarding—SNMP CEF-MIB Support
Perform the following tasks to configure Cisco Express Forwarding—SNMP CEF-MIB Support.
•Configuring the Router to Use SNMP (required)
•Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications (required)
•Configuring SNMP Notifications for Cisco Express Forwarding Events (required)
•Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notification (optional)
Configuring the Router to Use SNMP
Perform the following task to configure the router to use SNMP.
Before you can use the Cisco Express Forwarding—SNMP CEF-MIB Support feature, you must configure the SNMP server for the router.
SUMMARY STEPS
1. enable
2. configure terminal
3. snmp-server community string [view view-name] [ro | rw] [ipv6 nacl] [access-list-number]
4. snmp-server community string2 rw
5. end
DETAILED STEPS
Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications
Perform the following task to configure an SNMP host to receive CISCO-CEF-MIBnotifications. Notifications provide information to assist you in the monitoring and managing of CEF operations.
SUMMARY STEPS
1. enable
2. configure terminal
3. snmp-server community string [ro | rw]
4. snmp-server community string2 rw
5. snmp-server host ip-address [vrf vrf-name] [traps | informs] [version {1 | 2c | 3
[auth | noauth | priv]}] community-string [udp-port port] cef6. end
DETAILED STEPS
What to Do Next
After you configure an SNMP host to receive the CISCO-CEF-MIB notifications, you can configure the notifications that you want to receive. See the "Configuring SNMP Notifications for Cisco Express Forwarding Events" section.
Configuring SNMP Notifications for Cisco Express Forwarding Events
Perform the following task to configure SNMP notifications for CEF events. You can complete the task through the use of CLI commands or SNMP commands.
Prerequisites
You need to configure an NMS or SNMP agent to receive the SNMPCISCO-CEF-MIB notification, see the "Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications" section
SUMMARY STEPS
Router CLI Commands
1. enable
2. configure terminal
3. snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]
4. snmp-server host ip-address [traps | informs] [version {1 | 2c | 3 [auth | noauth | priv]}] community-string cef
5. end
SNMP Commands
1. setany version ip-address community-string cefPeerStateChangeNotifEnable.0 -i TruthValue
2. setany version ip-address community-string cefPeerFIBStateChangeNotifEnable.0 -i TruthValue
3. setany version ip-address community-string cefResourceFailureNotifEnable.0 -i TruthValue
4. setany version ip-address community-string cefInconsistencyNotifEnable.0 -i TruthValue
DETAILED STEPS: Router CLI Commands
Command or Action PurposeStep 1
enable
Example:Router> enable
Enables privileged EXEC mode.
•Enter your password if prompted.
Step 2
configure terminal
Example:Router# configure terminal
Enters global configuration mode.
Step 3
snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]
Example:Router(config)# snmp-server enable traps cef resource-failure
Enables Cisco Express Forwarding support of SNMP notifications on an NMS.
•The peer-state change keyword enables the sending of CISCO-CEF-MIB SNMP notifications for changes in the operational state of CEF peers.
•The resource-failure keyword enables the sending of CISCO-CEF-MIB SNMP notifications for resource failures that affect CEF operations.
•The inconsistency keyword enables the sending of CISCO-CEF-MIB SNMP notifications for inconsistencies that occur when routing information is updated from the Routing Information Base (RIB) to the CISCO-CEF-MIB on the RP and to the CISCO-CEF-MIB on the line cards.
You can set the throttling interval for sending inconsistency notifications, see the "Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notification" section.
•The peer-fib-state-change keyword enables the sending of CISCO-CEF-MIB SNMP notifications for changes in the operational state of the CEF peer FIB.
Step 4
snmp-server host ip-address [traps | informs] [version {1 | 2c | 3 [auth | noauth | priv]}] community-string cef
Example:Router(config)# snmp-server host 10.56.125.47 informs version 2c public cef
Specifies the recipient of an SNMP notification operation.
•The ip-address argument is the IP address or IPv6 address of the SNMP notification host.
The SNMP notification host is typically a network management station (NMS or SNMP manager). This host is the recipient of the SNMP traps or informs.
•The traps keyword specifies that notifications should be sent as traps. This is the default.
•The informs keyword specifies that notifications should be sent as informs.
•The version keyword specifies the version of the SNMP used to send the traps. The default is 1.
If you use the version keyword, one of the following keywords must be specified:
–1—SNMPv1. This option is not available with informs.
–2c—SNMPv2C.
–3—SNMPv3. The most secure model because it allows packet encryption with the priv keyword. The default is noauth.
•One of the following three optional security level keywords can follow the version 3 keywords:
–auth—Enables Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) packet authentication.
–noauth—Specifies that the noAuthNoPriv security level applies to this host. This is the default security level for SNMPv3.
–priv—Enables Data Encryption Standard (DES) packet encryption (also called "privacy").
•The community-string argument specifies that a password-like community string be sent with the notification operation.
•The cef keyword specifies that the Cisco Express Forwarding notification type is to be sent to the host. If no type is specified, all available notifications are sent.
Step 5
end
Example:Router(config)# end
Exits to privileged EXEC mode.
DETAILED STEPS: SNMP Commands
Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notification
Perform the following task to configure the throttling interval for CISCO-CEF-MIB inconsistency notifications.
Configuring a throttling interval allows some time before an inconsistency notification is sent during the process of updating forwarding information from the Routing Information Base (RIB) to the RP and to the line card databases. As these databases are updated, inconsistencies might result, due to the asynchronous nature of the distribution mechanism for these databases. The throttling interval allows fleeting inconsistencies to resolve themselves before sending an inconsistence notification.
SUMMARY STEPS
Router CLI Commands
1. enable
2. configure terminal
3. snmp-server enable traps cef inconsistency
4. snmp mib cef throttling-interval seconds
5. end
SNMP Commands
1. setany version ip-address community-string cefNotifThrottlingInterval.0 -i seconds
DETAILED STEPS
:
DETAILED STEPS: SNMP Commands
Configuration Examples for Cisco Express Forwarding—SNMP CEF-MIB Support
This section contains the following configuration examples for the Cisco Express Forwarding—SNMP CEF-MIB Support feature:
•Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications: Example
•Configuring SNMP Notifications for Cisco Express Forwarding Events: Example
•Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications: Example
Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications: Example
The following example shows how to configure an SNMP host to receive CISCO-CEF-MIB notifications:
configure terminal!
snmp-server community public ro
snmp-server community private rw
snmp-server host 10.56.125.47 informs version 2vc public cef
endThis example sets up SNMP host 10.56.125.47 to receive CISCO-CEF-MIB notifications as informs.
Configuring SNMP Notifications for Cisco Express Forwarding Events: Example
This section contains examples for configuring SNMP notifications for CEF events using the CLI and using SNMP commands.
Configuring SNMP Notifications for Cisco Express Forwarding Events Using the CLI: Example
This example shows how to use the CLI to configure CISCO-CEF-MIB SNMP notifications to be sent to host 10.56.125.47 as informs for changes in CEF peer states and peer FIB states, for CEF resource failures, and for inconsistencies in CEF events:
configure terminal!
snmp-server community public ro
snmp-server host 10.56.125.47 informs version 2c public cef
!snmp-server enable traps cef peer-state-changesnmp-server enable traps cef peer-fib-state-changesnmp-server enable traps cef inconsistencysnmp-server enable traps cef resource-failureendConfiguring SNMP Notifications for Cisco Express Forwarding Events Using SNMP Commands: Example
This example shows the use of SNMP command to configure CISCO-CEF-MIB SNMP notifications to be sent to host 10.56.125.47 for changes in CEF peer states and peer FIB states, for CEF resource failures, and for inconsistencies in CEF events:
setany -v2c 10.56.125.47 public cefPeerStateChangeNotifEnable.0 -i 1
setany -v2c 10.56.125.47 public cefPeerFIBStateChangeNotifEnable.0 -i 1
setany -v2c 10.56.125.47 public cefResourceFailureNotifEnable.0 -i 1setany -v2c 10.56.125.47 public cefInconsistencyNotifEnabled.0 -i 1Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications: Example
This example shows the configuration of a throttling interval for the sending of CEF inconsistency notifications to the SNMP host using CLI commands and SNMP commands. The throttling interval is the amount of time that passes between the time that the inconsistency occurs and the sending of the notification to the SNMP host.
Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications Using CLI Commands: Example
This example shows the addition of a throttling interval of 1000 seconds for the sending of CEF inconsistency notifications to the SNMP host using CLI commands:
configure terminal!
snmp-server community public ro
snmp-server host 10.56.125.47 informs version 2c public cef
!snmp-server enable traps cef peer-state-changesnmp-server enable traps cef peer-fib-state-changesnmp-server enable traps cef inconsistencysnmp-server enable traps cef resource-failure!snmp mib cef throttling-interval 1000endConfiguring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notifications Using SNMP Commands: Example
This example shows the addition of a throttling interval of 1000 seconds for the sending of CEF inconsistency notifications to the SNMP host using an SNMP command:
setany -v2c 10.56.125.47 public cefNotifThrottlingInterval.0 -1 1000Additional References
The following sections provide references related to the Cisco Express Forwarding—SNMP CEF-MIB Support feature.
Related Documents
Related Topic Document TitleCommands for configuring and managing Cisco Express Forwarding
Overview of Cisco Express Forwarding
Tasks for configuring Cisco Express Forwarding
Standards
Standard TitleNo new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
—
MIBs
RFCs
RFC TitleRFC 3291
Textual Conventions for Internet Network Addresses
RFC 3413
Simple Network Management Protocol (SNMP) Applications
Technical Assistance
Command Reference
This section documents new and modified commands only.
•snmp mib cef throttling-interval
snmp mib cef throttling-interval
To set the throttling interval for the CEF-MIB inconsistency notifications, use the snmp mib cef throttling-interval command in global configuration mode. To remove the throttling interval, use the no form of this command.
snmp mib cef throttling-interval seconds
no snmp mib cef throttling-interval seconds
Syntax Description
Command Default
Throttling is disabled by default (throttling interval is set to 0 seconds).
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command in conjunction with the snmp-server enable traps cef inconsistency command to set the time elapsed between the occurrence of a Cisco Express Forwarding database inconsistencies and the time when you want to receive an inconsistency notification.
If you set the throttling interval to 0 seconds, throttling is disabled.
Examples
The following example shows how to set the throttling interval for CEF-MIB inconsistency notification to 300 seconds:
configure terminal!snmp-server enable traps cef inconsistencysnmp mib cef throttling-interval 300Related Commands
snmp-server enable traps cef
To enable Cisco Express Forwarding (CEF) support of Simple Network Management Protocol (SNMP) notifications on a network management system (NMS), use the snmp-server enable traps cef command in global configuration mode. To disable Cisco Express Forwarding support of SNMP notifications, use the no form of this command.
snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]
no snmp-server enable traps cef [peer-state-change] [resource-failure] [inconsistency] [peer-fib-state-change]
Syntax Description
Command Default
All CEF-MIB notifications are disabled by default.
Command Modes
Global configuration
Command History
Usage Guidelines
You can use this command to enable CEF-MIB SNMP notifications that correspond to specific Cisco Express Forwarding events. To send the notifications to an NMS or host system, you need to configure the snmp-server host command with the cef keyword.
You can enable all CEF-MIB SNMP notifications if you enter the snmp-server enable traps cef command without entering an optional keyword.
Examples
The following example shows how to enable the router to send CEF peer state changes and forwarding inconsistencies as informs to the NMS with IP address 10.56.125.47 and to use the community string defined as public:
configure terminal!snmp-server enable traps cef peer-state-change inconsistencysnmp-server host 10.56.125.47 informs version 2c publicRelated Commands
snmp-server host
To specify the recipient of a Simple Network Management Protocol (SNMP) notification operation, use the snmp-server host command in global configuration mode. To remove the specified host from the configuration, use the no form of this command.
snmp-server host {hostname | ip-address} [vrf vrf-name] [traps | informs] [version {1 | 2c | 3 [auth | noauth | priv]}] community-string [udp-port port] [notification-type]
no snmp-server host {hostname | ip-address} [vrf vrf-name] [traps | informs] [version {1 | 2c | 3 [auth | noauth | priv]}] community-string [udp-port port] [notification-type]
Syntax Description
Command Default
This command is disabled. No notifications are sent.
Command Modes
Global configuration
Command History
Usage Guidelines
If you enter this command with no keywords, the default is to send all trap types to the host. No informs will be sent to the host.
The no snmp-server host command with no keywords disables traps, but not informs, to the host. To disable informs, use the no snmp-server host informs command.
Note If the community-string is not defined using the snmp-server community command prior to using this command, the default form of the snmp-server community command will automatically be inserted into the configuration. The password (community-string) used for this automatic configuration of the snmp-server community will be the same as specified in the snmp-server host command. This automatic command insertion and use of passwords is the default behavior for Cisco IOS Release 12.0(3) and later releases.
SNMP notifications can be sent as traps or inform requests. Traps are unreliable because the receiver does not send acknowledgments when it receives traps. The sender cannot determine if the traps were received. However, a SNMP entity that receives an inform request acknowledges the message with a SNMP response protocol data unit (PDU). If the sender never receives the response, the inform request can be sent again. Thus, informs are more likely to reach their intended destination.
Compared to traps, informs consume more resources in the agent and in the network. Unlike a trap, which is discarded as soon as it is sent, an inform request must be held in memory until a response is received or the request times out. Also, traps are sent only once; an inform may be retried several times. The retries increase traffic and contribute to a higher overhead on the network.
If you do not enter a snmp-server host command, no notifications are sent. To configure the router to send SNMP notifications, you must enter at least one snmp-server host command. If you enter the command with no keywords, all trap types are enabled for the host.
To enable multiple hosts, you must issue a separate snmp-server host command for each host. You can specify multiple notification types in the command for each host.
When multiple snmp-server host commands are given for the same host and kind of notification (trap or inform), each succeeding command overwrites the previous command. Only the last snmp-server host command will be in effect. For example, if you enter an snmp-server host inform command for a host and then enter another snmp-server host inform command for the same host, the second command will replace the first.
The snmp-server host command is used in conjunction with the snmp-server enable command. Use the snmp-server enable command to specify which SNMP notifications are sent globally. For a host to receive most notifications, at least one snmp-server enable command and the snmp-server host command for that host must be enabled.
Some notification types cannot be controlled with the snmp-server enable command. For example, some notification types are always enabled and others are enabled by a different command. For example, the linkUpDown notifications are controlled by the snmp trap link-status command. These notification types do not require an snmp-server enable command.
A notification-type option's availability depends on the router type and Cisco IOS software features supported on the router. For example, the envmon notification type is available only if the environmental monitor is part of the system. To see what notification types are available on your system, use the command help ? at the end of the snmp-server host command.
The vrf keyword allows you to specify the notifications being sent to a specified IP address over a specific VRF. The VRF defines a VPN membership of a customer so data is stored using the VPN.
Regarding Notification-Type Keywords
The notification-type keywords used in the snmp-server host command do not always match the keywords used in the corresponding snmp-server enable traps command. For example, the notification keyword applicable to Multiprotocol Label Switching Protocol (MPLS) traffic engineering tunnels is specified as mpls-traffic-eng (containing two hyphens and no intervening spaces). The corresponding parameter in the snmp-server enable traps command is specified as mpls-traffic-eng (containing an intervening space and a hyphen).
This syntax difference is necessary to ensure that the command-line interface (CLI) interprets the notification-type keyword of the snmp-server host command as a unified, single-word construct, which preserves the capability of the snmp-server host command to accept multiple notification-type keywords in the command line. The snmp-server enable traps commands, however, often use two-word constructs to provide hierarchical configuration options and to maintain consistency with the command syntax of related commands. Table 20 maps some examples of snmp-server enable traps commands to the keywords used in the snmp-server host command.
Table 20 Notification Keywords and Corresponding SNMP Enable Traps Commands
SNMP Enable Traps Command SNMP Host Command Keywordsnmp-server enable traps l2tun session
l2tun-session
snmp-server enable traps mpls ldp
mpls-ldp
snmp-server enable traps mpls traffic-eng1
mpls-traffic-eng
snmp-server enable traps mpls vpn
mpls-vpn
1 See the Cisco IOS Multiprotocol Label Switching Command Reference for documentation of this command.
Examples
If you want to configure a unique SNMP community string for traps but prevent SNMP polling access with this string, the configuration should include an access list. The following example shows how to name a community string comaccess and number an access list 10:
Router(config)# snmp-server community comaccess ro 10Router(config)# snmp-server host 172.20.2.160 comaccessRouter(config)# access-list 10 deny any
Note The sign (@) is used as a delimiter between the community string and the context in which it is used. For example, specific VLAN information in BRIDGE-MIB may be polled using community@VLAN_ID (for example, public@100) where 100 is the VLAN number.
The following example shows how to send RFC 1157 SNMP traps to a host specified named myhost.cisco.com. Other traps are enabled, but only SNMP traps are sent because only snmp is specified in the snmp-server host command. The community string is defined as comaccess.
Router(config)# snmp-server enable trapsRouter(config)# snmp-server host myhost.cisco.com comaccess snmpThe following example shows how to send the SNMP and Cisco environmental monitor enterprise-specific traps to address 172.30.2.160 using the community string public:
Router(config)# snmp-server enable traps snmpRouter(config)# snmp-server enable traps envmonRouter(config)# snmp-server host 172.30.2.160 public snmp envmonThe following example shows how to enable the router to send all traps to the host myhost.cisco.com using the community string public:
Router(config)# snmp-server enable trapsRouter(config)# snmp-server host myhost.cisco.com publicThe following example will not send traps to any host. The BGP traps are enabled for all hosts, but only the ISDN traps are enabled to be sent to a host. The community string is defined as public.
Router(config)# snmp-server enable traps bgpRouter(config)# snmp-server host myhost.cisco.com public isdnThe following example shows how to enable the router to send all inform requests to the host myhost.cisco.com using the community string public:
Router(config)# snmp-server enable trapsRouter(config)# snmp-server host myhost.cisco.com informs version 2c publicThe following example shows how to send HSRP MIB informs to the host specified by the name myhost.cisco.com. The community string is defined as public.
Router(config)# snmp-server enable traps hsrpRouter(config)# snmp-server host myhost.cisco.com informs version 2c public hsrpThe following example shows how to send all SNMP notifications to company.com over the VRF named trap-vrf using the community string public:
Router(config)# snmp-server host company.com vrf trap-vrf publicThe following example shows how to configure an IPv6 SNMP notification server with the IPv6 address 2001:0DB8:0000:ABCD:1 using the community string public:
Router(config)# snmp-server host 2001:0DB8:0000:ABCD:1 version 2c public udp-port 2012
The following example shows how to specify VRRP as the protocol using the community string public:
Router(config)# snmp-server enable traps vrrpRouter(config)# snmp-server host myhost.cisco.com traps version 2c public vrrpThe following example shows how to send all Cisco Express Forwarding informs to the notification receiver with the IP address 10.56.125.47 using the community string public:
Router(config)# snmp-server enable traps cefRouter(config)# snmp-server host 10.56.125.47 informs version 2c public cefRelated Commands
Feature Information for Cisco Express Forwarding—SNMP CEF-MIB Support
Table 21 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS 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 Table 21 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release. Unless noted otherwise, subsequent releases of that Cisco IOS software also support that feature.
Table 21 Feature Information for Cisco Express Forwarding—SNMP CEF-MIB Support
Feature Name Releases Feature InformationCisco Express Forwarding—SNMP CEF-MIB Support
12.2(31)SB2
The Cisco Express Forwarding—SNMP CEF-MIB Support feature introduces the CISCO-CEF-MIB that allows management applications through the use of the Simple Network Management Protocol (SNMP) to configure and monitor Cisco Express Forwarding (CEF) operational data and to provide notification when CEF encounters specific configured events. This module describes how to use the CISCO-CEF-MIB to manage and monitor objects related to CEF operation.
In 12.2(31)SB2, this feature was introduced on the Cisco 10000.
The following sections provide information about this feature:
•Cisco Express Forwarding Functional Overview
•CEF Information Managed by the CISCO-CEF-MIB
•CISCO-CEF-MIB Object Groups and Related Tables
•Brief Description of the Tables in the CISCO-CEF-MIB
•CEF Configuration and Monitoring Operations Available Through the CISCO-CEF-MIB
•Configuring the Router to Use SNMP
•Configuring an SNMP Host to Receive CISCO-CEF-MIB Notifications
•Configuring SNMP Notifications for Cisco Express Forwarding Events
•Configuring the Throttling Interval for CISCO-CEF-MIB Inconsistency Notification
The following commands were introduced or modified by this feature: snmp mib cef throttling-interval, snmp-server enable traps cef, and snmp-server host.
Glossary
informs—A type of notification message that is more reliable than a conventional trap notification message, because the informs message notification requires acknowledgment, but a trap notification does not.
IPC—Inter-Process Communication. The protocol used by routers that support distributed packet forwarding. The Cisco IOS version of IPC provides a reliable ordered delivery of messages using an underlying platform driver transport or User Date Protocol (UDP) transport protocol. Cisco IOS software IPC services allow line cards (LCs) and the central route processor (RP) in a distributed system, such as a Cisco 7500 series router, to communicate with each other by exchanging messages from the RP to the LCs. Communication messages are also exchanged between active and standby RPs. The IPC messages include configuration commands, responses to the configuration commands, and other events that are reported by an LC to the RP.
MIB—Management Information Base. A database of network management information that is used and maintained by a network management protocol such as Simple Network Management Protocol (SNMP). The value of a MIB object can be changed or retrieved by the use of SNMP commands, usually through a network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.
NMS—network management station. A powerful, well-equipped computer (typically an engineering workstation) that is used by a network administrator to communicate with other devices in the network. An NMS is typically used to manage network resources, gather statistics, and perform a variety of network administration and configuration tasks. In the context of SNMP, an NMS is a device that performs SNMP queries to the SNMP agent of a managed device to retrieve or modify information.
notification—A message sent by a Simple Network Management Protocol (SNMP) agent to a network management station, console, or terminal to indicate that a significant network event has occurred. See also trap.
SNMP—Simple Network Management Protocol. A network management protocol used almost exclusively in TCP/IP networks. SNMP enables a user to monitor and control network devices, manage configurations, collect statistics, monitor performance, and ensure network security.
SNMP communities—Authentication scheme that enables an intelligent network device to validate SNMP requests.
SNMPv2c—Version 2c of the Simple Network Management Protocol. SNMPv2c supports centralized as well as distributed network management strategies and includes improvements in the Structure of Management Information (SMI), protocol operations, management architecture, and security.
trap—A message sent by an SNMP agent to a network management station, console, or terminal to indicate that a significant network event has occurred. Traps (notifications) are less reliable than inform requests, because the receiver of the trap does not send an acknowledgment of receipt; furthermore, the sender of the trap cannot determine if the trap was received. See also notification.
XDR—External Data Representation. Information elements inside Inter-Process Communication (IPC) messages in which Cisco Express Forwarding updates are encoded in distributed packet forwarding.
Note See Internetworking Terms and Acronyms for terms not included in this glossary.
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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
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