Release 15.5SY Supervisor Engine 6T Software Configuration Guide

SNMP IfIndex Persistence

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• Prerequisites for SNMP IfIndex Persistence
• Restrictions for SNMP IfIndex Persistence
• Information About SNMP IfIndex Persistence
• Default Settings for SNMP IfIndex Persistence
• How to Configure SNMP IfIndex Persistence

Note ● For complete syntax and usage information for the commands used in this chapter, see these publications:

http://www.cisco.com/en/US/products/ps11846/prod_command_reference_list.html

• Cisco IOS Release 15.4SY supports only Ethernet interfaces. Cisco IOS Release 15.4SY does not support any WAN features or commands.

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

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Prerequisites for SNMP IfIndex Persistence

None.

Restrictions for SNMP IfIndex Persistence

None.

Information About SNMP IfIndex Persistence

The SNMP ifIndex persistence feature provides an interface index (ifIndex) value that is retained and used when the switch reboots. The ifIndex value is a unique identifying number associated with a physical or logical interface.

There is no requirement in the relevant RFCs that the correspondence between particular ifIndex values and their interfaces be maintained when the switch reboots, but many applications (for example, device inventory, billing, and fault detection) require maintenance of this correspondence.

You can poll the switch at regular intervals to correlate the interfaces to the ifIndexes, but it is not practical to poll constantly. The SNMP ifIndex persistence feature provides permanent ifIndex values, which eliminates the need to poll interfaces.

The following definitions are based on RFC 2233, “The Interfaces Group MIB using SMIv2.” The following terms are values in the Interfaces MIB (IF-MIB):

• ifIndex —A unique number (greater than zero) that identifies each interface for SNMP identification of that interface.
• ifName —The text-based name of the interface, for example, “ethernet 3/1.”
• ifDescr— A description of the interface. Recommended information for this description includes the name of the manufacturer, the product name, and the version of the interface hardware and software.

Default Settings for SNMP IfIndex Persistence

SNMP ifIndex persistence is disabled by default.

How to Configure SNMP IfIndex Persistence

• Enabling SNMP IfIndex Persistence Globally
• Enabling and Disabling SNMP IfIndex Persistence on Specific Interfaces

Enabling and Disabling SNMP IfIndex Persistence on Specific Interfaces

To enable SNMP ifIndex persistence only on a specific interface, perform this task:

 

	Command	Purpose
Step 1	Router(config)# interface { vlan vlan_ID } | { type slot/port } | { port-channel port_channel_number }	Selects an interface to configure.
Step 2	Router(config-if)# snmp ifindex persist	Enables SNMP ifIndex persistence on the specified interface.
Step 3	Router(config-if)# exit	Exits interface configuration mode.

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Note The [no] snmp ifindex persistence interface command cannot be used on subinterfaces. A command applied to an interface is automatically applied to all the subinterfaces associated with that interface.

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In the following example, SNMP ifIndex persistence is enabled for Ethernet interface 3/1 only:

router(config)# interface ethernet 3/1

router(config-if)# snmp ifindex persist

router(config-if)# exit

 

In the following example, SNMP ifIndex persistence is disabled for Ethernet interface 3/1 only:

router(config)# interface ethernet 3/1

router(config-if)# no snmp ifindex persist

router(config-if)# exit