Cisco Cisco IOS Software Release 12.0(11)S
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Cisco IOS Release 12.0(11)S
Interface Index Persistence
This feature module describes the enhancement to Cisco IOS Release 12.0(11)S which allows interfaces
to be identified with unique values which will remain constant even when a device is rebooted. These
interface identification values are used for network monitoring and management using Simple Network
Management Protocol (SNMP). This document includes the following sections:
to be identified with unique values which will remain constant even when a device is rebooted. These
interface identification values are used for network monitoring and management using Simple Network
Management Protocol (SNMP). This document includes the following sections:
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Feature Overview
One of the most commonly used identifiers used in SNMP-based network management applications is
the interface index (ifIndex) value. IfIndex is a unique identifying number associated with a physical or
logical interface; as far as most software is concerned, the ifIndex is the "name" of the interface.
the interface index (ifIndex) value. IfIndex is a unique identifying number associated with a physical or
logical interface; as far as most software is concerned, the ifIndex is the "name" of the interface.
Though there is no requirement in the relevant RFCs that the correspondence between particular ifIndex
values and their interfaces be maintained across reboots, increasingly applications such as device
inventory, billing, and fault detection depend on this correspondence being maintained.
values and their interfaces be maintained across reboots, increasingly applications such as device
inventory, billing, and fault detection depend on this correspondence being maintained.
Cisco IOS Release 12.0(11)S adds support for an ifIndex value that can persist across reboots, allowing
users to avoid the workarounds previously required for consistent interface identification.
users to avoid the workarounds previously required for consistent interface identification.
It is currently possible to poll the router at regular intervals to correlate the interfaces to the ifIndex, but
it is not practical to poll this interface constantly. If this data is not correlated constantly however, the
data may be made invalid because of a re-boot or new card inserted into the router in between polls.
Therefore, ifIndex persistence is the only way to guarantee data integrity.
it is not practical to poll this interface constantly. If this data is not correlated constantly however, the
data may be made invalid because of a re-boot or new card inserted into the router in between polls.
Therefore, ifIndex persistence is the only way to guarantee data integrity.
IfIndex persistence means that the mapping between the ifDescr object values and the ifIndex object
values (generated from the IF-MIB) will be retained across reboots.
values (generated from the IF-MIB) will be retained across reboots.