Cisco Express Forwarding 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 Cisco Express Forwarding operation are the FIB and adjacency tables.

Cisco Express Forwarding uses adjacency tables to prepend Layer 2 addressing information. An 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. Cisco Express Forwarding discovers and solves adjacencies and populates the adjacency tables.

Note	The CISCO-CEF-MIB prefix database and its related database can be very large. Therefore, executing a command that displays the prefix table could take a considerable amount of time.

Command-line interface (CLI) show commands are available to obtain Cisco Express Forwarding operational information. Managing Cisco Express Forwarding using the CLI can be a time-consuming task. The increasing capacity of Cisco routers makes parsing the show commands output to obtain the needed Cisco Express Forwarding 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 Cisco Express Forwarding operation using SNMP. In addition, you can configure SNMP to notify you if Cisco Express Forwarding encounters errors.

The CISCO-CEF-MIB introduced with the Cisco Express Forwarding--SNMP CEF-MIB Support feature gives you real-time access to operational information stored in the FIB and adjacency tables, switching statistics, and information on resource failures. The feature enables you to configure parameters related to Cisco Express Forwarding 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.

Cisco Express Forwarding is available in all Cisco routers. However, CISCO-CEF-MIB support of Cisco Express Forwarding management is dependent on the 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, Cisco IOS Release 12.2(33)SRC,and Cisco IOS Release 12.2(33)SB manages Cisco Express Forwarding instances running on the Route Processor (RP). Information about Cisco Express Forwarding running on the line cards is available to the RP in reference to Cisco Express Forwarding peers only.

The CISCO-CEF-MIB supports configuration and monitoring for both IP versions, IP Version 4 (IPv4) and IP Version 6 (IPv6).

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:

• Cisco Express Forwarding administrative and operational states as displayed in the output of the show ip cef summary command
• Notifications for Cisco Express Forwarding events: Cisco Express Forwarding state changes, Cisco Express Forwarding failures (with a predefined reason), and Route Processor (RP) and line card inconsistencies
• Parameters related to Cisco Express Forwarding for the associated interface as displayed by the show cef interface command
• Line card Cisco Express Forwarding states and line card Cisco Express Forwarding FIB states in the Linecard table as displayed by the show cef linecardcommand
• Cisco Express Forwarding statistics: switching statistics, punt counters and punt-to-host counters as displayed by the show ip cef switching statscommand, and per-prefix counters and nonrecursive counters
• IPv4 and IPv6 notification, when Cisco Express Forwarding is switched between disable and enable and between Cisco Express Forwarding and distributed Cisco Express Forwarding

The SNMP CISCO-CEF-MIB provides managed objects that enable a network administrator to configure the following:

• Cisco Express Forwarding and distributed Cisco Express Forwarding administration status
• Cisco Express Forwarding accounting-related parameters
• Cisco Express Forwarding load sharing-related parameters
• Traffic-related configuration parameters

The SNMP CISCO-CEF-MIB allows the configuration and management of objects related to Cisco Express Forwarding. 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 Cisco Express Forwarding object groups. These tables provide information about prefixes, forwarding paths, adjacencies, output chain elements (OCEs), prefix-based statistics, information about Cisco Express Forwarding configuration, consistency checkers, switching statistics, and managed objects specific to line card-specific.

The CISCO-CEF-MIB also defines Cisco Express Forwarding 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.

• The CEF FIB Summary table (cefFIBSummaryTable) contains the number of forwarding prefixes for both IPv4 and IPv6 protocols. It is 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 CEF 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 Cisco Express Forwarding: administration and operational status, accounting-related configuration parameters, load-sharing algorithms and IDs, and traffic statistics parameters.
• CEF Resource table (cefResourceTable) contains information about resources for Cisco Express Forwarding: the memory status of the process memory pool and reasons for the Cisco Express Forwarding resource failure notifications.
• CEF Interface table (cefIntTable) contains the interface-specific Cisco Express Forwarding parameters: 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 Cisco Express Forwarding information related to peers on a managed line card: line card operational state and the number of times 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 Statistics 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 parameters 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 theOperations Available Through the CISCO-CEF-MIB for information about the specific objects available through the CISCO-CEF-MIB tables.

The figure below shows the contents of the CISCO-CEF-MIB main tables and the relationships of the tables to one another.

Figure 1

CISCO-CEF-MIB Main Tables, Table Contents, and Relationships

You can use SNMP getand setcommands to configure and monitor Cisco Express Forwarding operations that are available through the CISCO-CEF-MIB tables. This section describes the configuration and monitoring operations for each table.

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF FIB Summary table (cefFIBSummaryTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Forwarding table (cefPrefixTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Longest Match Prefix table (cefLMPrefixTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Path table (cefPathTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Adjacency Summary table (cefAdjSummaryTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Adjacency table (cefAdjTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Forwarding Element Selection table (cefFESelectionTable).

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Cfg table (cefCfgTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Resource table (cefResourceTable).

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Interface table (cefIntTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Peer table (or Linecard table) (cefPeerTable).

The table below lists the Cisco Express Forwarding monitoring operation and associated MIB object provided by the CEF Peer FIB table (cefPeerFIBTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Prefix Length Statistics table (cefStatsPrefixTable).

The table below lists the Cisco Express Forwarding monitoring operations and associated MIB objects provided by the CEF Switching Statistics table (cefSwitchingStatsTable).

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF IP Prefix Consistency Global Checker group (cefCCGlobalTable).

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Consistency Checker Type table (cefCCTypeTable).

The table below lists the Cisco Express Forwarding configuration and monitoring operations and associated MIB objects provided by the CEF Inconsistency Record table (cefInconsistencyRecordTable).

The table below lists the Cisco Express Forwarding operations associated with the CISCO-CEF-MIB objects that enable the sending of Cisco Express Forwarding notifications.

You can enable or disable these notifications through the MIB or by entering a CLI command. The table below 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.

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

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] cef

6.    end

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

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

1.    enable

2.    configure terminal

3.    snmp-server enable traps cef inconsistency

4.    snmp mib cef throttling-interval seconds

5.    end

1.    setany version ip-address community-string cefNotifThrottlingInterval.0 -i seconds