Cisco Cisco IOS Software Release 12.0 S

Platform: Cisco 7200 series, Cisco 7500/RSP series, Cisco 12000 series

Multiprotocol label switching (MPLS) is a packet forwarding methodology that uses a short, 
fixed-length value (called a label) in packets to enable the determination of the next hop for transporting 
packets through an MPLS network. Two label switching routers (LSRs) must agree on the definition of 
the labels used to forward network traffic between and through them. This common understanding of 
labels is achieved through a set of procedures embodied in the Label Distribution Protocol (LDP). The 
LDP enables an LSR to inform other LSRs of the label bindings it has made, thereby distributing label 
binding information to peer devices for the purpose of supporting hop-by-hop forwarding along 
normally routed paths.

For LDP to be used to the best advantage in an MPLS network, the MPLS Label Distribution Protocol 
MIB (MPLS LDP MIB) has been implemented in conjunction with MPLS and LDP. Designed as a 
network management aid, the MPLS LDP MIB is based on an Internet Engineering Task Force (IETF) 
draft that defines objects in a structured and standardized label-switching database. 

The information in the MPLS LDP MIB is accessible by means of any network management utility that 
supports the Simple Network Management Protocol (SNMP). The SNMP-based code in a network 
management utility incorporates a layered structure for supporting the MPLS LDP MIB that is similar 
to that built into Cisco IOS software for supporting MIBs.

For further information, see the Cisco document MPLS Label Distribution Protocol (LDP) MIB at the 
following location:

This feature has been ported from Cisco IOS Release 12.0ST.

Platforms: Cisco 7200 series, Cisco 7500/RSP series, Cisco 12000 series

When you enable MPLS LDP MIB notification functionality by issuing the snmp-server enable traps 
mpls ldp command, notification messages are generated and sent to a designated network management 
station (NMS) in the network to signal the occurrence of specific events within Cisco IOS software.

The MPLS LDP MIB objects involved in Label Distribution Protocol (LDP) status transitions and event 
notifications include the following:

mplsLdpSessionUp

mplsLdpSessionDown

mplsLdpPathVectorLimitMismatch

mplsLdpFailedInitSessionThresholdExceeded

This implementation of the MPLS LDP MIB traps for Cisco IOS Release 12.0(22)S is limited to 
read-only (RO) permission for MIB objects, except for MIB object 
mplsLdpSessionUpDownTrapEnable, which, for purposes of this release, has been extended to be 
writeable by the Simple Network Management Protocol (SNMP) agent.