Cisco Cisco IOS Software Release 12.0(23)S

This document describes the Multiprotocol Label Switching (MPLS) enhancements to the existing 
interfaces Management Information Base (MIB) (RFC 2233) to support an MPLS layer. This layer 
provides counters and statistics specifically for MPLS.

This document includes the following major sections:

The Interfaces MIB (IF MIB) provides a Simple Network Management Protocol (SNMP) based method 
for managing interfaces. Each entry in the IF MIB establishes indexing, statistics, and stacking 
relationships among underlying physical interfaces, subinterfaces, and Layer 2 protocols that exist 
within Cisco IOS.

The enhancements add an MPLS layer to the IF MIB as a Layer 2 protocol to provide statistics for traffic 
encapsulated as MPLS on an interface. In this new structure, MPLS-specific data, such as 
MPLS-encapsulated traffic counters and the MPLS maximum transmission unit (MTU), resides on top 
of the underlying physical or virtual interface to allow separation from non-MPLS data.

The enhancements also allow you to view indexing, statistics, and stacking relationships using the 
ifStackTable. MPLS layer interfaces are stacked above the underlying physical or virtual interface that 
is actually forwarding the MPLS traffic. MPLS traffic engineering tunnels are then stacked above those 
MPLS layers.

12.0(23)S

This feature was introduced in Cisco IOS Release 12.0(23)S.