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This feature module describes the addition and enhancement of Simple Network Management Protocol (SNMP) Management Information Base modules (MIBs) for interfaces in Cisco IOS Software Release 12.1(2)T. This document includes the following sections:
Please see the Glossary for definitions of any unfamiliar terms or acronyms.
This feature module documents enhancements made to the Interfaces Group MIB module (IF-MIB) and the addition of the Ethernet-like Interfaces MIB module (ETHERLIKE-MIB) in Cisco IOS Release 12.1(2)T. These MIB enhancements bring the IF-MIB into compliance with RFC2233, and implements support for RFC2665 in the ETHERLIKE-MIB. Additionally, you can now configure SNMP to use either the existing Cisco implementation of linkUp / linkDown traps or the new implementation consistent with Internet Engineering Task Force (IETF) standards. This configuration is achieved through the use of a new Cisco IOS CLI command.
Until this enhancement was introduced, linkUp and linkDown traps in Cisco IOS have been defined in the Cisco Interface Capability MIB module (CISCO-IF-CAPABILITY.my) as follows:
VARIATION linkUp -- TRAP-TYPE
-- OBJECTS { ifIndex, ifDescr, ifType, locIfReason }
DESCRIPTION "A linkUp trap signifies that the sending
protocol entity recognizes that one of the
communication links represented in the agent's
configuration has come up."
VARIATION linkDown -- TRAP-TYPE
-- OBJECTS { ifIndex, ifDescr, ifType, locIfReason }
DESCRIPTION "A linkDown trap signifies that the sending
protocol entity recognizes a failure in one of
the communication links represented in the
agent's configuration."
However, RFC2233 defines linkUp and linkDown traps in the Interfaces Group MIB module (IF-MIB.my) as follows:
linkDown NOTIFICATION-TYPE
OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
::= { snmpTraps 3 }
linkUp NOTIFICATION-TYPE
OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
::= { snmpTraps 4 }
Starting with Cisco IOS Release 12.1(2)T, you can configure your router to begin using the new RFC2233 IETF standards-based implementation by using the snmp-server trap link ietf command. This command is disabled by default to allow you to continue using the current Cisco implementation of linkUp/linkDown traps if you so choose.
However, please note that when using the existing Cisco object definitions, an arbitrary value is used for the locIfReason object in linkUp/linkDown traps for sub-interfaces, which may give you unintended results. This is because the locIfReason object is not defined for sub-interfaces in the current Cisco implementation, which uses OLD-CISCO-INTERFACES-MIB.my.
If you do not enable this functionality, the link trap varbind list will consist of {ifIndex, ifDescr, ifType, locIfReason}. After you enable this functionality with the snmp-server trap link ietf command, the varbind list will consist of {inIndex, ifAdminStatus,ifOperStatus, if Descr, ifType}. The locIfReason object will also be conditionally included in this list depending on whether meaningful information can be retrieved for that object. A configured sub-interface will generate retrievable information. On non-HWIDB interfaces, there will be no defined value for locIfReason, so it will be omitted from the trap message.
Other updates to the IF-MIB module have also been made to comply with RFC2233. These changes include the addition of the ifCounterDiscontinuityTime object, and the addition of basic support for ifTableLastChange (updated OIR drivers are planned in a future release for full ifTableLastChange support).
Support for RFC2665 in the ETHERLIKE-MIB was achieved through the addition of two new objects in the dot3StatsTable: dot3StatsSymbolErrors and dot3StatsDuplexStatus. This modification also meets the requirements of the Data Over Cable System Interface Specification (DOCSIS) Operations Support System Interface Specification (OSSI) specification (as defined in oss-n-99090). Please note that the dot3StatsTable is the only dot3 table required for DOCSIS and RFC2665 compliance.
Compliance with RFC2233 and RFC2665
The enhancement to the IF-MIB allows Cisco IOS to support RFC2233, and the addition of the ETHERLIKE-MIB allows Cisco IOS to support RFC2665. Prior to this release, Cisco IOS supported only RFC1573 and RFC2358, respectively. Support of these standards documents allows other future enhancements, such as the planned full Data-Over-Cable Service Interface Specification (DOCSIS) 1.0 compliance on the Cisco uBR7200 platform.
linkUp/linkDown Trap Generation for Subinterfaces
The enhancement to the IF-MIB allows linkUp and linkDown SNMP traps for subinterfaces to be generated correctly, while permitting unaffected customers to continue using the earlier Cisco implementation.
There are no known memory or performance impacts for this feature.
The ETHERLIKE-MIB is supported on all platforms using Cisco IOS software. The IF-MIB is supported on the following platforms:
Standards
As of the time of this writing (March 2000), RFC2233 and RFC2665 are classified as IETF "Proposed Standards" in RFC2600. RFC2600 is the March 2000 edition of of the "Internet Official Protocols Standards" RFC, also known as "STD 1." The most recent edition of STD1 may be copied via FTP from the FTP.ISI.EDU server using the FTP username "anonymous" and FTP password "guest": navigate to the file "in-notes/std/std1.txt". Most current web browsers will also also access using the following address: ftp://ftp.isi.edu/in-notes/std/std1.txt
The MIB enhancements described in this document bring these MIBs into compliance with the DOCSIS OSSI requirements for cable interfaces.
MIBs
The updates to the Interface Group MIB and the Ethernet-like Interface MIB are reflected in the following files:
The Ethernet-like MIB modules were introduced in Cisco IOS Release 12.0(9)SC (the cable-specific release for Cisco uBR7200 series routers).
For lists of supported MIBs by platform and to download MIB modules, see the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
RFCs are available from a variety of Internet sources, including http://www.ietf.org.
To utilize the MIBs described in this feature module you must configure SNMP on your system. The configuration task below assumes you will be using Cisco IOS or a network management system (NMS) such as CiscoWorks to monitor the performance of your network. For information on these topics, see the documents listed in the Related Documents section, or the documentation which came with your network management application.
See the following section for configuration tasks for the Interface MIB Enhancement feature. Configuration of this feature is optional on your system, and is disabled by default.
To enable the use of the new object list for SNMP linkUp/linkDown traps, use the following commands, starting in privileged EXEC mode:
| Command | Purpose | |
|---|---|---|
Step 1 | Router#configure terminal | Enters global configuration mode. |
Step2 | Router(config)#snmp-server trap link ietf | Enables SNMP traps which are compliant with RFC2233. |
Step3 | Router(config)#end | Ends the current configuration session and returns you to privileged EXEC mode. |
Use the more system:running-config command in privileged EXEC mode to verify that the command is in your running configuration file.
To monitor SNMP trap activity in real-time for the purposes of troubleshooting, use the SNMP debug commands, including the debug snmp packet command. For documentation of SNMP debug commands, see the Release 12.1 Cisco IOS Debug Command Reference, available on Cisco Connection Online (CCO) at
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121sup/index.htm, or on the Cisco Documentation CD-ROM.
The following example shows the SNMP related output before the IETF compliant implementation is enabled, a configuration session it which it is enabled, and the changed output after the configuration:
Router#more system:running config. . .!snmp-server engineID local 00000009000000A1616C2056snmp-server community public ROsnmp-server community private RW!. . .Router#conf termEnter configuration commands, one per line. End with CNTL/Z.Router(config)#snmp-server trap link ietfRouter(config)#endRouter#more system:running config. . .!snmp-server engineID local 00000009000000A1616C2056snmp-server community public ROsnmp-server community private RWsnmp-server trap link ietf!. . .
This section documents the new command that enables the Interfaces Group MIB Enhancements feature. All other existing SNMP-related commands are documented in the Cisco IOS Configuration Fundamentals Command Reference.
To enable linkUp/linkDown SNMP traps which are compliant with RFC2233, use the snmp-server trap link command in global configuration mode. To disable IETF compliant functionality and revert to the older Cisco implementation of linkUp/linkDown traps, use the no form of this command.
snmp-server trap link ietf
Syntax Description
ietf This required keyword indicates to the command parser that you would like to link functionality of SNMP traps to the Internet Engineering Task Force (IETF) standard (as opposed to the current Cisco implementation).
Defaults
This command is disabled by default.
Command Modes
Global configuration mode
Command History
12.1(2)T This command was introduced.
Release
Modification
Usage Guidelines
The snmp-server trap link ietf command is used to configure your router to use the RFC2233 IETF standards-based implementation of linkUp/linkDown traps. This command is disabled by default to allow you to continue using the earlier Cisco implementation of linkUp/linkDown traps if you so choose.
However, please note that when using the earlier Cisco object definitions linkUp/linkDown traps are not generated correctly for sub-interfaces.
Examples
The following example shows the enabling of the RFC2233 linkUp/linkDown traps, starting in privileged EXEC mode:
configure terminal snmp-server trap link ietf end
Related Commands
debug snmp packets Displays information about every SNMP packet sent or received by the router for the purposes of troubleshooting.
Command
Description
CLI---The Cisco IOS Command-Line Interface. The CLI is the primary user interface for entering Cisco IOS commands on Cisco devices (such as routers).
DOCSIS---Data-Over-Cable Service Interface Specification. DOCSIS defines interface requirements for Cable Modems (CM) and Cable Modem Termination Systems (CMTS) involved in high-speed data distribution over cable television networks. CM certification and CMTS qualification is determined by Cable Television Laboratories, Inc. (CableLabs). Full CM and CMTS certification is in development for the Cisco uBR900 Series and the Cisco uBR7200 Series. See also OSSI.
ETHERLIKE-MIB---The "Ethernet-like Interface Types MIB", as defined in RFC2665.
IETF---Internet Engineering Task Force. The IETF is the body (supervised by the Internet Architecture Board) that defines Internet operating standards such as SNMP MIBs, and publishes RFCs for use by the Internet community. The IETF's web site address is http://www.ietf.org.
IF-MIB---The Interfaces Group MIB. The current specification for the IF-MIB is found in RFC2233.
MIB---Management Information Base. The MIBs referred to in this document are MIB modules. These modules contain definitions of management information for use by SNMP network management systems.
OID---Object Identifier. The values for OIDs are defined in specific MIB modules.
OSSI---Operations Support System Interface. OSSI is a specific DOCSIS specification. For example, "DOCSIS OSSI 1.0" defines the Network Management requirements for support a DOCSIS 1.0 environment.
RFC---Requests For Comments. RFCs are a series of documents used as the primary means for communicating information about the Internet. Some RFCs are designated by the Internet Architecture Board (IAB) as Internet standards. Most RFCs document protocol specifications such as Telnet and FTP, but some are humorous or historical. RFCs are available online from numerous sources, but a primary source is http://www.rfc-editor.org/.
Posted: Thu May 25 13:26:01 PDT 2000
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