Cisco Cisco IOS Software Release 12.0(11)S

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Interface Index Persistence
Feature Overview
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Cisco IOS Release 12.0(11)S
Benefits
Association of Interfaces with Traffic Targets for Network Management
The IfIndex Persistence feature allows for greater accuracy when collecting and processing network 
management data by uniquely identifying input and output interfaces for traffic flows and SNMP 
statistics. By relating each interface to a known entity (such as a ISP customer), network management 
data can be more effectively utilized.
Accuracy for Mediation, Fault Detection, and Billing
With the international growth and reliance of network data being used for usage-based billing, network 
planning, policy enforcement, and trending analysis, it becomes increasingly important to be extremely 
accurate when collecting and processing network management data. The ifIndex information is used to 
identify input and output interfaces for traffic flows and SNMP statistics. Not being able to reliably 
relate each interface to a known entity such as a customer invalidates the data.
Restrictions
The interface-specific ifIndex persistence command ([no] snmp ifindex persistence) can not be used 
on subinterfaces. A command applied to an interface is automatically applied to all the subinterfaces 
associated with that interface.
Testing indicates approximately 25 bytes of NVRAM storage is used by this feature per interface. 
There 
may be some boot delay on platforms with lower CPU speeds.
Related Features and Technologies
SNMP (Simple Network Management Protocol)
RMON (Remote Monitoring)
Expression MIB
Event MIB
Related Documents
The “Configuring SNMP Support” chapter of the Cisco IOS Configuration Fundamentals 
Configuration Guide, Release 12.1 
(available on CCO)
The “SNMP Commands” chapter of the Cisco IOS Configuration Fundamentals Command 
Reference, Release 12.1 
(available on CCO)
“Ethernet-like Interfaces MIB and Interfaces Group MIB Enhancements” Feature Module, 
Cisco IOS Release 12.1(2)T (available on CCO).
RFC 2233, “The Interfaces Group MIB using SMIv2” 
RFCs are available from a variety of internet sources. The primary source is the IETF’s web site at 
http://www.ietf.org