Cisco 7600 Series Router Software Configuration Guide, Cisco IOS Release 15S

Configuring SNMP IfIndex Persistence

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This chapter describes how to configure the SNMP ifIndex persistence feature on Cisco 7600 series routers.

Note For complete syntax and usage information for the commands used in this chapter, refer to the Cisco 7600 Series Routers Command References at this URL:

http://www.cisco.com/en/US/products/hw/routers/ps368/prod_command_reference_list.html

This chapter consists of these sections:

• Understanding SNMP IfIndex Persistence
• Configuring SNMP IfIndex Persistence

Understanding SNMP IfIndex Persistence

The SNMP ifIndex persistence feature provides an interface index (ifIndex) value that is retained and used when the router 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 router reboots, but many applications (for example, device inventory, billing, and fault detection) require maintenance of this correspondence.

You can poll the router 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.

Configuring SNMP IfIndex Persistence

These sections describe how to configure SNMP ifIndex persistence:

• Enabling SNMP IfIndex Persistence Globally (Optional)
• Enabling and Disabling SNMP IfIndex Persistence on Specific Interfaces (Optional)

Note To verify that ifIndex commands have been configured, use the more system:running-config command.

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 1 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.
	Router(config-if)# no snmp ifindex persist	Disables SNMP ifIndex persistence on the specified interface.
Step 3	Router(config-if)# exit	Exits interface configuration mode.

1.type = any supported interface type.

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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