Table Of Contents
Interface Index Display and Interface Alias Long Name Support for SNMP
Related Features and Technologies
Configuring IfAlias Long Name Support
Verifying IfAlias Long Name Support
Monitoring and Maintaining SNMP Interface Identification Values
Configuring IfAlias Long Name Support Example
Interface Index Display and Interface Alias Long Name Support for SNMP
First Published: 12.2(2)TLast Updated: February 28, 2006History for the Interface Index Display and Interface Alias Long Name Support for SNMP Feature
12.2(2)T
This feature was introduced.
12.2(28)SB
This feature was integrated into Cisco IOS Release 12.2(28)SB.
Finding Support Information for Platforms and Cisco IOS Software Images
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Contents
Feature Overview
The Simple Network Management Protocol (SNMP) is the language for communication between a managing system running a network management application and a managed system running an agent. Between them they share the concept of a Management Information Base (MIB) that defines the information the agent can make available to the manager.
SNMP network management is based on the Internet Network Management Framework. This framework defines a model in which a managing system called a manager communicates with a managed system. The manager—typically referred to as the Network Management System, or NMS —runs a network management application, and the managed system runs an agent, which answers requests from the manager, and generates notifications to the manager.
The Management Information Base (MIB) defines all the information about a managed system that a NMS can view or modify. The MIB is located on the managed system and can consist of standard and proprietary portions. The agent and manager each have their own view of the MIB. The NMS can be configured to periodically update its MIB view from all managed agents.
The MIB shared by the manager and agent typically consists of a collection of MIB modules. (MIB modules are also referred to as "MIBs".) For example, the Interfaces MIB (IF-MIB.my) is a MIB module found in the MIB that exists for most Cisco IOS software-based devices.
An SNMP MIB is an abstract data base, that is, it is a conceptual specification for information that management application can read and modify. The SNMP agent translates between the internal data structures and formats of the managed system and the external data structures and formats defined for the MIB. The SNMP MIB is organized as a tree structure with conceptual tables.
A MIB object, also sometimes called variable, is a leaf in the MIB tree. Each leaf represent an individual item of data. Examples of objects are counters and protocol status. Leaf objects are connected to branch points.
The Interface Index Display for SNMP feature introduces new commands and command modifications that allow advanced users of SNMP to view information about the interface registrations directly on the managed agent. (For the purposes of this document, the agent is the routing device running Cisco IOS software.) In other words, the commands in this feature allow the user to display MIB information from the agent without using an external NMS.
This feature addresses three objects in the Interfaces MIB: the ifIndex object, the ifAlias object, and the ifName object. For the complete definition of these objects, see the IF-MIB.my file, available from the Cisco SNMPv2 MIB website at ftp://ftp.cisco.com/pub/mibs/v2/.
The ifIndex object (ifEntry 1) is called the Interface Index. The Interface Index (ifIndex) is a unique value, greater than zero, which identifies each interface (or subinterface) on the managed device. This value becomes the interface index identification number.
A new Cisco IOS software command, show snmp mib ifmib ifindex, allows the user to view the SNMP Interface Index Identification numbers assigned to interfaces and subinterfaces using the CLI. This provides a way to view these values without the need for a Network Management System.
The ifAlias object (ifXEntry 18) is called the Interface Alias. The Interface Alias (ifAlias) is a user-specified description of an interface used for SNMP network management. The ifAlias is an object in the Interfaces Group MIB (IF-MIB) which can be set by a network manager to "name" an interface. The ifAlias value for an interface or subinterface can be set using the description command in interface configuration mode or subinterface configuration mode, or by using a Set operation from an NMS. Prior to this release, ifAlias descriptions for subinterfaces were limited to 64 characters. (The OLD-CISCO-INTERFACES-MIB allows up to 255 characters for the locIfDescr MIB variable, but this MIB does not support subinterfaces.) A new Cisco IOS software command, snmp ifmib ifalias long, configures the system to handle IfAlias descriptions of up to 256 characters. IfAlias descriptions appear in the output of the show interfaces command.
The ifName object ( ifXEntry 1) is the textual name of the interface. The value of this object is the name of the interface as assigned by the local device and is suitable for use in commands entered at the CLI. If there is no local name, or this object is otherwise not applicable, then this object contains a zero-length string. No commands introduced by this feature impact the ifName object, but it is discussed here to show its relation to the ifIndex and ifAlias objects. The purpose of the ifName object is to cross reference the CLI representation of a given interface.
The show snmp mib command shows all objects in the MIB on a Cisco device (similar to a mibwalk). The objects in the MIB tree are sorted using lexical ordering. This means that object identifiers are sorted in sequential, numerical order. Lexical ordering is important when using the GetNext operation from an NMS because these operations takes an object identifier (OID) or a partial OID as input and returns the next object from the MIB tree based on the lexical ordering of the tree.
The show snmp mib command will display the instance identifiers for all the MIB objects on the system. The instance identifier is the final part of the OID. An object can have one or more instance identifiers. Before displaying the instance identifier, the system attempts to find the best match with the list of table names. The MIB module table names are registered when the system initializes.
This feature also introduces the Circuit Interface Identification Persistence for SNMP feature. The Circuit Interface MIB (CISCO-CIRCUIT-INTERFACE-MIB) provides a MIB object (cciDescr) which can be used to identify individual circuit-based interfaces for SNMP monitoring.
The Circuit Interface Identification Persistence for SNMP feature maintains the user-defined name of the circuit (defined in the cciDescr object) across reboots, allowing for the consistent identification of circuits.
The Circuit Interface Identification Persistence for SNMP feature is a supplement to the Interface Index Persistence feature introduced in Cisco IOS Release 12.1(3)T and Cisco IOS Release 12.0(11)S. Circuit Interface Identification Persistence is enabled with the snmp mib persist circuit command in the global configuration mode. Use this command if you need to consistently identify circuits using SNMP across reboots. This command is disabled by default because this feature uses NVRAM memory.
Benefits
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The show snmp mib ifmib ifindex command in the EXEC mode allows you to display the Interfaces MIB ifIndex values directly on your system without the need for a network management system.
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Related Features and Technologies
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Prerequisites
The tasks presented in this document assume you have SNMP enabled on your system. For information on configuring SNMP, see the documents listed in the "Related Documents" section.
Configuration Tasks
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Configuring IfAlias Long Name Support
To configure the IF-MIB to retain ifAlias values of longer than 64 characters, use the following command in global configuration mode:
Router(config)# snmp ifmib ifalias long
Configures the Interfaces MIB (IF-MIB) on the system to return ifAlias values of longer than 64 characters to a Network Management System.
To configure the ifAlias for an interface, use the following command in interface configuration mode or subinterface configuration mode:
Verifying IfAlias Long Name Support
To confirm that IfAlias Long Name Support has been enabled, you can optionally perform the following steps:
Step 1
Step 2
Note that the description for interfaces also appears in the output of the more system:running config command in the EXEC mode.
Troubleshooting Tips
An alternative to using the ifAlias value for the identification of interfaces across reboots is to use the cciDescr object in the Cisco Circuit Interface MIB (CISCO-CIRCUIT-INTERFACE-MIB.my). Note that this MIB object can be used only for circuit-based interfaces such as ATM or Frame Relay interfaces. Cisco IOS Release 12.2(2)T introduces the Circuit Interface Identification Persistence for SNMP feature, which maintains the user-defined name of the circuit (defined in the cciDescr object) across reboots, allowing for the consistent identification of circuit-based interfaces.
Monitoring and Maintaining SNMP Interface Identification Values
To monitor SNMP interface identification values, use the following commands in EXEC mode, as needed:
Router# show snmp mib
Displays a list of the MIB module instance identifiers registered on your system.
Router# show snmp mib ifmib ifindex [interface-type] [slot/][port-adapter/][port]
Displays the Interfaces MIB ifIndex values registered on your system for all interfaces or the specified interface.1
Router# show interface [interface-type] [slot/][port-adapter/][port]
Displays system information for all interfaces or the specified interface, including the user-specified description (ifAlias).1
1 The availability of the slot and port-adapter arguments depends on the hardware setup of your system.
Configuration Examples
This section provides the following configuration example:
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Configuring IfAlias Long Name Support Example
In the following example a long description is applied to ethernet interface in slot 1, port adapter 0, and port 0:
Router# configure terminalRouter(config)# interface Ethernet1/0/0Router(config-if)# description ethernet1/0/0 this is a test of a description that exceeds 64 characters in lengthRouter(config-if)# ip address 192.168.134.55 255.255.255.0Router(config-if)# no ip directed-broadcastRouter(config-if)# no ip route-cache distributedAssuming that ifAlias long name support is not yet enabled (the default), the following example shows the results of a mibwalk operation from an NMS:
***** SNMP QUERY STARTED *****...ifXEntry.18.10 (octets) (zero-length)ifXEntry.18.11 (octets) ethernet1/0/0 this is a test of a description that exceeds 64 chifXEntry.18.12 (octets) (zero-length)...The following output shows the description that is displayed at the CLI:
Router# show interface Ethernet0/0/0Ethernet1/0/0 is administratively down, line protocol is downHardware is Lance, address is 0010.7b4d.7046 (bia 0010.7b4d.7046)Description: ethernet1/0/0 this is a test of a description that exceeds 64 chhMTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,reliability 252/255, txload 1/255, rxload 1/255...In the following example, ifAlias long name support is enabled, and the description is displayed again:
Router(config)# snmp ifmib ifalias longRouter(config)# interface Ethernet1/0/0Router(config-if)# description ethernet1/0/0 this is a test of a description that exceeds 64 characters in lengthRouter(config)# endRouter# show interface Ethernet1/0/0Ethernet1/0/0 is administratively down, line protocol is downHardware is Lance, address is 0010.7b4d.7046 (bia 0010.7b4d.7046)Description: ethernet1/0/0 this is a test of a description that exceeds 64 characters in lengthMTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,reliability 252/255, txload 1/255, rxload 1/255...***** SNMP QUERY STARTED *****...ifXEntry.18.10 (octets) (zero-length)ifXEntry.18.11 (octets) ethernet1/0/0 this is a test of a description that exceeds 64 characters in lengthifXEntry.18.12 (octets) (zero-length)...Additional References
The following sections provide references related to Interface Index Display and Interface Alias Long Name Support for SNMP.
Related Documents
Configuring SNMP Support
"Configuring SNMP Support" chapter in the Cisco IOS Configuration Fundamentals Configuration Guide, Release 12.2
SNMP Commands
"SNMP Commands" chapter in the Cisco IOS Configuration Fundamentals Command Reference, Release 12.2T
Standards
MIBs
RFCs
Technical Assistance
Command Reference
This section documents modified commands only.
snmp ifmib ifalias long
To configure the system to handle IfAlias descriptions of up to 256 characters, use the snmp ifmib ifalias long command in global configuration mode. To limit the IfAlias description to 64 characters, use the no form of this command.
snmp ifmib ifalias long
no snmp ifmib ifalias long
Syntax Description
This command has no arguments or keywords.
Command Default
The ifAlias description is limited to 64 characters.
Command Modes
Global configuration
Command History
12.2(2)T
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
The ifAlias object (ifXEntry 18) of the Interfaces MIB (IF-MIB) is called the Interface Alias. The Interface Alias (ifAlias) is a user-specified description of an interface used for Simple Network Management Protocol (SNMP) network management. The ifAlias is an object in the Interfaces Group MIB (IF-MIB) which can be set by a network manager to "name" an interface.
The ifAlias value for an interface or subinterface can be set using the description command in interface configuration mode or subinterface configuration mode, or by using a Set operation from an NMS. Prior to the introduction of this command, ifAlias descriptions for subinterfaces were limited to 64 characters. (The OLD-CISCO-INTERFACES-MIB allows up to 255 characters for the locIfDescr MIB variable, but this MIB does not support subinterfaces.) IfAlias descriptions appear in the output of the show interfaces command in EXEC mode, and in the output of the more system: running-config or show running-config commands in EXEC mode.
Examples
In the following example, the system is configured to retain and return ifAlias values of up to 256 characters in length:
Router(config)# snmp ifmib ifalias longRelated Commands
snmp mib persist circuit
To globally enable circuit interface identification values that will remain constant across reboots for use by SNMP, use the snmp mib persist circuit command in global configuration mode. To globally disable circuit interface persistence for SNMP, use the no form of this command.
snmp mib persist circuit
no snmp mib persist circuit
Syntax Description
This command has no arguments or keywords.
Command Default
Disabled.
Command Modes
Global configuration
Command History
12.2(2)T
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
The Circuit Interface MIB (CISCO-CIRCUIT-INTERFACE-MIB) provides a MIB object (cciDescr) that can be used to identify individual circuit-based interfaces for SNMP monitoring. A consistent value for specific circuits is useful for network management applications that use SNMP.
Circuit interface identification persistence maintains the user-defined name of the circuit across reboots by retaining the value of the cciDescr object in the Circuit Interface MIB. Circuit interface identification persistence is enabled using the snmp mib persist circuit global configuration command. This command is disabled by default because this feature uses NVRAM memory.
Examples
In the following example, circuit interface identification persistence is enabled for all interfaces:
Router(config)# snmp mib persist circuitRelated Commands
show snmp mib
To display a list of the MIB module instance identifiers (OIDs) registered on your system, use the show snmp mib command in EXEC mode.
show snmp mib
Syntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
12.2(2)T
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
SNMP management information is viewed as a collection of managed objects, residing in a virtual information store, termed the Management Information Base (MIB). Collections of related objects are defined in MIB modules. These modules are written using a subset of OSIs Abstract Syntax Notation One (ASN.1), termed the Structure of Management Information (SMI).
This command is intended for network administrators who are familiar with the SMI and ASN.1 syntax.
While this command can be used to display a list of MIB object identifiers (OIDs) registered on the system, the use of a network management system (NMS) application is the recommended alternative for gathering this information.
The show snmp mib command will display the instance identifiers for all the MIB objects on the system. The instance identifier is the final part of the OID. An object can have one or more instance identifiers. Before displaying the instance identifier, the system attempts to find the best match with the list of table names. The MIB module table names are registered when the system initializes.
The definitions for the OIDs displayed by this command can be found in the relevant RFCs and MIB modules. For example, RFC 1907 defines the system.x, sysOREntry.x, snmp.x, and snmpTrap.x OIDs, and this information is supplemented by the extensions defined in the CISCO-SYSTEM-MIB.
Tip
Examples
The following is sample output from the show snmp mib command:
Router# show snmp mibsystem.1system.2sysUpTimesystem.4system.5system.6system.7system.8sysOREntry.2sysOREntry.3sysOREntry.4interfaces.1ifEntry.1ifEntry.2ifEntry.3ifEntry.4ifEntry.5ifEntry.6ifEntry.7ifEntry.8ifEntry.9ifEntry.10ifEntry.11--More--...captureBufferEntry.2captureBufferEntry.3captureBufferEntry.4captureBufferEntry.5captureBufferEntry.6captureBufferEntry.7capture.3.1.1eventEntry.1eventEntry.2eventEntry.3eventEntry.4eventEntry.5eventEntry.6eventEntry.7logEntry.1logEntry.2logEntry.3logEntry.4rmon.10.1.1.2rmon.10.1.1.3rmon.10.1.1.4rmon.10.1.1.5rmon.10.1.1.6rmon.10.1.1.7rmon.10.2.1.2rmon.10.2.1.3rmon.10.3.1.2--More--...rmon.192.168.1.1rmon.192.168.1.2rmon.192.168.1.3rmon.192.168.1.2rmon.192.168.1.3rmon.192.168.1.4rmon.192.168.1.5rmon.192.168.1.6rmon.192.168.1.2rmon.192.168.1.3rmon.192.168.1.4rmon.192.168.1.5rmon.192.168.1.6rmon.192.168.1.7rmon.192.168.1.8rmon.192.168.1.9dot1dBase.1dot1dBase.2dot1dBase.3dot1dBasePortEntry.1dot1dBasePortEntry.2dot1dBasePortEntry.3dot1dBasePortEntry.4--More--...ifXEntry.1ifXEntry.2ifXEntry.3ifXEntry.4ifXEntry.5ifXEntry.6ifXEntry.7ifXEntry.8ifXEntry.9ifXEntry.10ifXEntry.11ifXEntry.12ifXEntry.13ifXEntry.14ifXEntry.15ifXEntry.16ifXEntry.17ifXEntry.18ifXEntry.19ifStackEntry.3ifTestEntry.1ifTestEntry.2--More--...Related Commands
show snmp mib ifmib ifindex
Displays SNMP Interface Index identification numbers (ifIndex values) for all the system interfaces or the specified system interface
show snmp mib ifmib ifindex
To display Simple Network Management Protocol (SNMP) Interface Index identification numbers (ifIndex values) for all the system interfaces or the specified system interface, use the show snmp mib ifmib ifindex command in privileged EXEC mode.
show snmp mib ifmib ifindex [interface-type] [slot/][port-adapter/][port]
Syntax Description
Command Default
The ifIndex values for all interfaces are displayed.
Command Modes
Priviliged EXEC
Command History
12.2(2)T
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
Usage Guidelines
The show snmp mib ifmib ifindex command allows you to display SNMP Interface Index identification numbers (ifIndex values) assigned to interfaces and subinterfaces using the command-line interface (CLI). This command provides a way to view these values without a network management station.
If a specific interface is not specified using the optional interface-type, slot, port-adapter, and port arguments, the ifDescr and ifIndex pairs of all interfaces and subinterfaces present on the system are shown.
Examples
The following example shows output for a specific interface:
Router# show snmp mib ifmib ifIndex Ethernet2/0Ethernet2/0: Ifindex = 2The following example shows output for all interfaces:
Router# show snmp mib ifmib ifindexATM1/0: Ifindex = 1ATM1/0-aal5 layer: Ifindex = 12ATM1/0-atm layer: Ifindex = 10ATM1/0.0-aal5 layer: Ifindex = 13ATM1/0.0-atm subif: Ifindex = 11ATM1/0.9-aal5 layer: Ifindex = 32ATM1/0.9-atm subif: Ifindex = 31ATM1/0.99-aal5 layer: Ifindex = 36ATM1/0.99-atm subif: Ifindex = 35Ethernet2/0: Ifindex = 2Ethernet2/1: Ifindex = 3Ethernet2/2: Ifindex = 4Ethernet2/3: Ifindex = 5Null0: Ifindex = 14Serial3/0: Ifindex = 6Serial3/1: Ifindex = 7Serial3/2: Ifindex = 8Serial3/3: Ifindex = 9Related Commands
Glossary
ifAlias—SNMP Interface Alias. The ifAlias is an object in the Interfaces MIB (IF-MIB). The ifAlias is an 'alias' name for the interface as specified by a network manager that provides a non-volatile description for the interface. For a complete definition, see the IF-MIB.my file.
ifIndex—SNMP Interface Index. The ifIndex is an object in the Interfaces MIB (IF-MIB). The ifIndex is a unique integer assigned to every interface (including subinterfaces) on the managed system when the interface registers with the IF-MIB. For a complete definition, see the IF-MIB.my file.
OID—MIB object identifier. An object identifier is expressed as a series of integers or text strings. Technically, the numeric form is the object name and the text form is the object descriptor. In practice, both are called object identifiers, or OIDs. For example, the object name for the interfaces MIB is `1.3.6.1.2.1.2', and the object descriptor is `iso.internet.mgmt.mib-2.interfaces', but either can be referred to as the OID. OIDs can also be expressed as a combination of the two, such as `iso.internet.2.1.2'.
Note
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.
© 2001, 2006 Cisco Systems, Inc. All rights reserved.
