Configuring SNMP IfIndex Persistence

This chapter describes how to configure the SNMP ifIndex persistence feature in Cisco IOS Release 12.2SX.

Note For complete syntax and usage information for the commands used in this chapter, see the Cisco IOS Master Command List, at this URL:

http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html

Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

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

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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 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.

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 SNMP IfIndex Persistence Globally

SNMP ifIndex persistence is disabled by default. To globally enableSNMP ifIndex persistence, perform this task:

Command
Purpose

Router(config)# snmp-server ifindex persist

Globally enables SNMP ifIndex persistence.


In the following example, SNMP ifIndex persistence is enabled for all interfaces: 

router(config)# snmp-server ifindex persist

 
   
 
     
    
   
 Disabling SNMP IfIndex Persistence Globally 
 
    
   
 To globally disable SNMP ifIndex persistence after enabling it, perform this task: 
 
    
   
 
 
   
 
    
 
      
      
      
 
        
        

          Command 
        
 		 
        
        

          Purpose 
        
 		 
      
 
      
 
       
Router(config)# no snmp-server ifindex persist 
 
       
 Globally disables SNMP ifIndex persistence. 
 		 
      
 
      
    
 
   
 
   
 
   
 
 
    
   
 In the following example, SNMP ifIndex persistence is disabled for all interfaces: 
 
    
   
 
    
router(config)# no snmp-server ifindex persist

 
   
 
     
    
    
   
 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} | {type1  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. 
 		 
      
 
      
    
 
    
 
      
      
 
       
 1 type = any supported interface type. 
 		 
      
 
      
    
 
   
 
   
 
 
   
 
     
   
 
   
 
    
   
 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. 
 
   
 
    
   
 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

 
   
 
     
    
   
 Clearing SNMP IfIndex Persistence Configuration from a Specific Interface 
 
    
   
 To clear the interface-specific SNMP ifIndex persistence setting and configure the interface to use the global configuration setting, perform this task: 
 
    
   
 
 
   
 
    
 
      
      
      
 
         
        
        

          Command 
        
 		 
        
        

          Purpose 
        
 		 
      
 
      
 
       
 Step 1  
 		 
       
Router(config)# interface type slot/port 
 
       
 Enters interface configuration mode for the specified interface. Note that the syntax of the interface command will vary depending on the platform you are using. 
 		 
      
 
      
 
       
 Step 2  
 		 
       
Router(config-if)# snmp ifindex clear 
 
       
 Clears any interface-specific SNMP ifIndex persistence configuration for the specified interface and returns to the global configuration setting. 
 		 
      
 
      
 
       
 Step 3  
 		 
       
Router(config-if)# exit 
 
       
 Exits interface configuration mode. 
 		 
      
 
      
    
 
   
 
   
 
 
    
    
    
   
 In the following example, any previous setting for SNMP ifIndex persistence on Ethernet interface 3/1 is removed from the configuration. If SNMP ifIndex persistence is globally enabled, SNMP ifIndex persistence will be enabled for Ethernet interface 3/1. If SNMP ifIndex persistence is globally disabled, SNMP ifIndex persistence will be disabled for Ethernet interface 3/1. 
 
    
   
 
    
router(config)# interface ethernet 3/1

 
   
 
    
   
 
    
router(config-if)# snmp ifindex clear

 
   
 
    
   
 
    
router(config-if)# exit

 
   
 
   
 
     
   
 
   
 
    
   
 Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page: 
 
    
   
 http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html 
 
    
   
 Participate in the Technical Documentation Ideas forum