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Cisco IOS Software Releases 12.2 S

MPLS Label Distribution Protocol (LDP)

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MPLS Label Distribution Protocol (LDP)

Table Of Contents

MPLS Label Distribution Protocol (LDP)

Feature Overview

Benefits

Related Documents

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Configuring LDP

Verifying LDP Configuration

Saving Configurations: MPLS/Tag Switching Commands

Configuration Examples

LDP Configuration Overview

Label Bindings, Label Spaces, and LDP Identifiers

LDP Discovery

LDP TCP Connections and Session Establishment

Configuring LDP for Packet Interfaces

Configuring LDP for Label-Controlled ATM Interfaces

Configuring LDP for Targeted Sessions

Transitioning a Network from TDP to LDP

CLI Command Summary

Command Reference

debug mpls atm-ldp api

debug mpls atm-ldp failure

debug mpls atm-ldp routes

debug mpls atm-ldp states

debug mpls ldp advertisements

debug mpls ldp backoff

debug mpls ldp bindings

debug mpls ldp messages

debug mpls ldp peer state-machine

debug mpls ldp prev-label

debug mpls ldp session io

debug mpls ldp session state-machine

debug mpls ldp targeted-neighbors

debug mpls ldp transport connections

debug mpls ldp transport events

mpls ip (global configuration)

mpls ip (interface configuration)

mpls label protocol (global configuration)

mpls label protocol (interface configuration)

mpls ldp address-message

mpls ldp advertise-labels

mpls ldp advertise-labels old-style

mpls ldp atm control-mode

mpls ldp atm vc-merge

mpls ldp backoff

mpls ldp discovery

mpls ldp discovery transport-address

mpls ldp explicit-null

mpls ldp holdtime

mpls ldp loop-detection

mpls ldp maxhops

mpls ldp neighbor

mpls ldp router-id

show mpls atm-ldp bindings

show mpls atm-ldp bindwait

show mpls atm-ldp capability

show mpls atm-ldp summary

show mpls interfaces

show mpls ip binding

show mpls ldp backoff

show mpls ldp bindings

show mpls ldp discovery

show mpls ldp neighbor

show mpls ldp parameters

Glossary


MPLS Label Distribution Protocol (LDP)


Feature History

Release
Modification

12.0(10)ST

This feature was introduced in Cisco IOS Release 12.0(10)ST, incorporating a new set of multiprotocol label switching (MPLS) CLI commands implemented for use with Cisco routers and switches. The CLI commands in this release reflected standard MPLS IETF command syntax and terminology, thus facilitating the orderly transition from a network using the Tag Distribution Protocol (TDP) to one using the Label Distribution Protocol (LDP). With respect to TDP, the MPLS CLI commands associated with this release were of three types: a) new CLI commands altogether for support of new MPLS/LDP functionality; b) functionally equivalent, but syntactically different, MPLS/LDP commands; and c) functionally and syntactically equivalent MPLS/LDP commands.

12.0(14)ST

This feature was integrated into Cisco IOS Release 12.0(14)ST. This release introduced several new MPLS CLI commands, provided support for MPLS VPNs by means of a new vrf vpn-name parameter in certain existing commands, and modified other commands to ensure consistent interpretation of associated prefix-access-list arguments by Cisco IOS.

12.1(2)T

This feature was integrated into Cisco IOS 12.2(2)T. Also, the debug mpls atm-ldp api, debug mpls atm-ldp routes, and debug mpls atm-ldp states commands were modified.

12.1(8a)E

This feature was integrated into Cisco IOS Release 12.1(8a)E.

12.2(2)T

This feature was integrated into Cisco IOS Release 12.2(2)T.

12.2(4)T

This feature was integrated into Cisco IOS Release 12.2(4)T. Also, support was added for Cisco MGX 8850 and MGX 8950 switches equipped with a Cisco MGX RPM-PR card, and the VPI range in the show mpls atm-ldp bindings and show mpls ip binding commands was changed to 4095.

12.0(21)ST

This feature was integrated into Cisco IOS Release 12.0(21)ST. This release introduced the implicit-withdraw keyword for the mpls ldp neighbor command. Also, support was added for the Cisco 10720 Internet router.

12.2(11)S

This feature was integrated into Cisco IOS Release 12.2(11)S.


This document describes the use of the MPLS Label Distribution Protocol (LDP), which enables peer label switch routers (LSRs) in an MPLS network to exchange label binding information for supporting hop-by-hop forwarding along normally routed paths. The document includes the following sections:

Feature Overview

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Configuring LDP

Verifying LDP Configuration

Saving Configurations: MPLS/Tag Switching Commands

Configuration Examples

Transitioning a Network from TDP to LDP

CLI Command Summary

Command Reference

Glossary

Feature Overview

Cisco's MPLS label distribution protocol (LDP), as standardized by the Internet Engineering Task Force (IETF) and as enabled by Cisco IOS software, allows the construction of highly scalable and flexible IP Virtual Private Networks (VPNs) that support multiple levels of services.

LDP provides a standard methodology for hop-by-hop, or dynamic label, distribution in an MPLS network by assigning labels to routes that have been chosen by the underlying Interior Gateway Protocol (IGP) routing protocols. The resulting labeled paths, called label switch paths or LSPs, forward label traffic across an MPLS backbone to particular destinations. These capabilities enable service providers to implement Cisco's MPLS-based IP VPNs and IP+ATM services across multivendor MPLS networks.

LDP provides the means for label switching routers (LSRs) to request, distribute, and release label prefix binding information to peer routers in a network. LDP enables LSRs to discover potential peers and to establish LDP sessions with those peers for the purpose of exchanging label binding information.

From an historical and functional standpoint, LDP is a superset of Cisco's prestandard Tag Distribution Protocol (TDP), which also supports MPLS forwarding along normally routed paths. For those features that LDP and TDP share in common, the pattern of protocol exchanges between network routing platforms is identical. The differences between LDP and TDP for those features supported by both protocols are largely embedded in their respective implementation details, such as the encoding of protocol messages, for example.

This release of LDP, which supports both the LDP and TDP protocols, provides the means for transitioning an existing network from a TDP environment to an LDP environment. Thus, you can run LDP and TDP simultaneously on any router platform. The routing protocol that you select can be configured on a per-interface basis for directly connected neighbors and on a per-session basis for nondirectly connected (targeted) neighbors. In addition, a label switch path (LSP) across an MPLS network can be supported by LDP on some hops and by TDP on other hops.

Benefits

LDP is an IETF standards tracking protocol. The primary benefit of LDP over the prestandard TDP protocol is that the former increases the number of platforms on which MPLS interoperability can be achieved.

Related Documents

For additional information about MPLS functionality running on routers or switches in a network, consult the following documentation:

Multiprotocol Label Switching on Cisco Routers—This feature, implemented on Cisco routers and ATM switches, combines the performance of Layer 2 (data link layer) switching with the scalability of Layer 3 (network layer) routing. This combination enables service providers to handle the explosive growth now occurring in network utilization and to differentiate services without having to alter the existing network infrastructure. MPLS supports the dynamic creation of different routes between source and destination nodes, thus enabling IP services to be delivered efficiently by means of Internet backbones.

MPLS Class of Service—This feature enables network administrators to provide a range of differentiated services across an MPLS network. Such services are implemented by means of an appropriate setting of the IP precedence bit in each transmitted IP packet.

MPLS Traffic Engineering and Enhancements—This feature enables an MPLS backbone to replicate and expand upon the traffic engineering capabilities of Layer 2 ATM and Frame Relay networks. In service provider and Internet service provider (ISP) backbones, traffic engineering provides an effective means of managing networks. Such backbones must support high transmission capacities and be resilient to link or node failures.

MPLS Virtual Private Networks (VPNs)—This feature enables users to deploy and administer IPv4 Layer 3, value-added services and business applications across a public network infrastructure. By deploying business applications on a broad scale over wide area networks (WANs), MPLS VPN users can reduce costs, increase revenue, and develop new business opportunities.

Supported Platforms

LDP is supported on the following platforms:

Cisco 7200 series routers

Cisco 7400 series routers

Cisco 7500 series routers

Determining Platform Support Through Cisco Feature Navigator

Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.

Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.

To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.

Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:

http://www.cisco.com/go/fn

Availability of Cisco IOS Software Images

Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.

Supported Standards, MIBs, and RFCs

This feature supports the IETF draft document entitled LDP Specification, draft-ietf-mpls-ldp-08.txt. The document can be accessed at the following URL:

http://www2.ietf.org/internet-drafts/draft-ietf-mpls-ldp-08.txt

Prerequisites

Label switching on a router requires that Cisco Express Forwarding (CEF) be enabled on that router. Refer to the chapters on CEF in the following documents for configuration information:

Cisco IOS Switching Services Release 12.2

Cisco IOS Command Reference Release 12.2

Configuration Tasks

In most situations, the use of LDP is associated with a router or a switch interface. To configure LDP to operate in an MPLS network with such an interface, you must:

1. Configure an MPLS application, such as hop-by-hop forwarding (sometimes called dynamic tag switching or dynamic MPLS), for the desired interfaces.

2. Configure the use of LDP for either of the following:

Label distribution for all interfaces

Label distribution for a specific interface

Configuring LDP

The table below illustrates the configuration tasks listed in the preceding section.

 
Command
Purpose

Step 1 

Router# configure terminal
Router(config)# ip cef [distributed]
Router(config)# interface interface
Router(config-if)# mpls ip

Configure MPLS hop-by-hop forwarding for an interface.

Step 2 

Router# configure terminal
Router(config)# mpls label protocol ldp

Configure the use of LDP on all interfaces.

The global mpls label protocol ldp command sets the default label distribution protocol for all interfaces to be LDP.

Step 3 

Router# configure terminal
Router(config)# interface interface
Router(config)# mpls label protocol ldp

Configure the use of LDP for a specific interface.

The interface mpls label protocol ldp command sets the label distribution protocol for the specified interface to be LDP, overriding any default set by the global mpls label protocol command in Step 2.


Note MPLS requires CEF.



Note The mpls ip command is equivalent to the tag-switching ip command. For more information about the mpls ip command, see Table 3.



Note Targeted sessions are usually not configured explicitly. For example, configuring mpls ip for a traffic engineering tunnel interface initiates establishment of a targeted session with the tunnel tail end.


Verifying LDP Configuration

To verify LDP configuration for an interface (Step 1 through Step 3 in the table above), issue the following commands:

show mpls interfaces—To verify that the interfaces in question have been configured to use LDP

show mpls ldp discovery—To verify that the interface is up and sending LDP Discovery Hello messages (as opposed to TDP Hello messages).

In addition, you can issue the show run command to verify the acceptance of the configuration commands.


Note If you issue the show run command as part of the verification process, be aware that commands you entered by typing mpls . . . may be shown as tag-switching . . . (see the next section entitled "Saving Configurations: MPLS/Tag Switching Commands."


Saving Configurations: MPLS/Tag Switching Commands

A number of configuration commands with both MPLS and tag switching forms will be supported during the transition from a tag switching environment to a standards-based MPLS environment. For example, the mpls ip command is equivalent to the tag-switching ip command.

Refer to Table 2 and Table 3 in the "CLI Command Summary" section for a complete list of commands related to LDP that have both MPLS and tag switching forms.

For commands that support both MPLS and tag switching forms, the tag switching form will be written to saved configurations during the transition period from TDP to LDP. Suppose, for example, that you configured an LC-ATM interface on a router by means of the following commands:

Router# configure terminal
Router(config)# interface ATM3/0.1 mpls
Router(config-if)# ip unnumbered Loopback0
router(config-if)# mpls ip
Router(config-if)# mpls label protocol ldp

In this example, the interface ATM3/0.1 mpls command and the mpls ip command have tag switching forms. After you enter these commands and save this configuration or display the running configuration by means of the show running command, the commands thus saved or displayed would appear as shown below:

interface ATM3/0.1 tag-switching
ip unnumbered Loopback0
tag-switching ip
mpls label protocol ldp

Writing the tag switching form of commands with both MPLS and tag switching forms to the saved configuration makes it possible for you to use a router software image that supports LDP to:

Modify and write interface configurations

At a later time, use interface configurations created by the LDP image with an earlier software version that does not support LDP

For the above example, older software that supports TDP, but not LDP, would be able to interpret all of the interface configuration commands, except for the mpls label protocol command. The older software would generate a warning message about the unrecognized command; nevertheless, the image would bring up the interface configured to run TDP.

Configuration Examples

This section provides the following configuration information:

LDP Configuration Overview

Configuring LDP for Packet Interfaces

Configuring LDP for Label-Controlled ATM Interfaces

Configuring LDP for Targeted Sessions

LDP Configuration Overview

The next three sections briefly describe aspects of MPLS LDP considered helpful to better understanding the configuration examples that follow later for packet interfaces, ATM interfaces, and targeted sessions.

Label Bindings, Label Spaces, and LDP Identifiers

An LDP label binding is an association between a destination prefix and a label. The label used in a label binding is allocated from a set of possible labels called a label space.

LDP supports two types of label spaces:

Interface-specific—An interface-specific label space uses interface resources for labels. For example, LC-ATM interfaces use VPIs/VCIs for labels. Depending on its configuration, an LDP platform may support zero, one, or more interface-specific label spaces.

Platform-wide—An LDP platform supports a single platform-wide label space for use by interfaces that can share the same labels. For Cisco platforms, all interface types except LC-ATM use the platform-wide label space.

LDP uses a 6-byte quantity called an LDP Identifier (or LDP ID) to name label spaces. The LDP convention is: a) the first four bytes of the LDP ID identify the LSR that owns the label space; and b) the last two bytes identify the label space within the LSR. For the platform-wide label space, the last two bytes of the LDP ID are always both 0.

The Cisco convention is that the first four bytes of an LDP ID is a platform IP address called the LDP router ID. The last two bytes are called the local label space ID. The display representation for an LDP ID takes the following form:

<LDP router ID> : <local label space ID>

The following are examples of this form:

133.0.0.33:0, 167.3.0.54:3

The LDP router ID is determined as described below. For purposes of this discussion, "S" represents the set of interfaces that are up and have IP addresses, while "I" represents the interface specified by the mpls ldp router-id command, if any.

a. If interface I is in S, then the IP address of interface I is the LDP router ID.

b. Otherwise, if there is a loopback interface in S, the largest IP address of the loopback addresses in S is the LDP router ID.

c. Otherwise, the largest IP address of the interfaces in S is the LDP router ID.

LDP Discovery

LDP discovery is a mechanism that reduces the amount of per-peer configuration required for LDP by enabling an LSR to discover potential LDP peers.

An LSR engages in discovery by periodically transmitting LDP Hello messages to signal its desire to advertise label bindings. The LSR sends the LDP Hello messages as UDP packets to the well known LDP port (646).

LDP defines two types of discovery which differ slightly from each other:

Basic discovery—This type is used to discover directly connected LDP LSRs. For basic discovery, an LSR sends Hellos messages to the "all routers on this subnet" multicast address on interfaces for which LDP has been configured.

Extended discovery—This type is used between nondirectly connected LDP LSRs. For extended discovery, an LSR sends targeted Hello messages to a specific IP address.

The Hello messages carry the LDP ID of the label space that the sending LSR wants to advertise, as well as other information.

When an LSR receives an LDP Hello message from another LSR, it considers that LSR and the specified label space to be "discovered." After two LSRs discover each other in this manner, they attempt to establish an LDP session (as described in the next section).

LDP TCP Connections and Session Establishment

LDP label distribution between two LSRs requires establishment of an LDP session. LSRs that have discovered each other establish an LDP session by:

Opening a TCP connection to be used to distribute label bindings.

For Cisco platforms, an LSR will use either its LDP router ID or the IP source address of its discovery Hello messages as the IP address for its endpoint of the TCP connection. The address it intends to use is specified to its LSR peer in the Hello messages it sends.

To establish the TCP connection, each LSR must have IP connectivity (that is, a route) to the IP address for the other LSR's endpoint for the connection.

Negotiating parameters for the LDP session.

Such parameters include the label distribution method (Downstream Unsolicited or Downstream on Demand) and other parameters.

After successfully opening the session TCP connection and agreeing to parameters for the session, LDP label distribution begins.

Configuring LDP for Packet Interfaces

Figure 1 shows a sample network for configuring the use of LDP for packet interfaces.


Note ATM point-to-point subinterfaces are considered "packet" interfaces when configuring LDP. ATM MPLS subinterfaces (and tag switching subinterfaces) are considered label-controlled ATM (LC-ATM) interfaces when configuring LDP (see the next section).


The three router configurations that follow accomplish the following:

Enable MPLS hop-by-hop forwarding for the POS links between Router 1 and Router 2 and between Router 1 and Router 3.

Configure the use of LDP for label distribution between Router 1 and Router 2.

Configure the use of TDP (the default) for label distribution between Router 1 and Router 3.

Configure a loopback interface and IP address for each LSR that can be used as the LDP router ID component of the LSR's LDP ID.

Figure 1 Configuration of LDP for Packet Interfaces


Note The configuration examples below show only the commands related to configuring LDP for Router 1, Router 2, and Router 3 in the sample network shown in Figure 1.


Router 1 Configuration

ip cef distributed                        !Assumes R1 supports distributed CEF 

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.11 255.255.255.255

interface POS3/0/0 
ip address 34.0.0.44 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
mpls label protocol ldp                   !Use LDP for this interface 

interface POS3/0/1 
ip address 45.0.0.44 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
                                          !Uses TDP (the default) 

Router 2 Configuration


ip cef distributed                        !Assumes R2 supports distributed CEF 

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.22 255.255.255.255

interface POS2/0/0 
ip address 34.0.0.33 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
mpls label protocol ldp                   !Use LDP for this interface 

Router 3 Configuration


ip cef                                    !Assumes R3 does not support 
                                          !distributed CEF 

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.33 255.255.255.255

interface POS1/0 
ip address 45.0.0.55 255.0.0.0
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
                                          !Uses TDP (the default) 

The LDP configuration for Router 1 uses the interface mpls label protocol ldp command because some of its interfaces use LDP and some use TDP. Another way to configure Router 1 is to use the global mpls label protocol ldp command to configure LDP as the default protocol for interfaces and use the interface mpls label protocol tdp command to configure TDP for the POS3/0/1 link to Router 3. This alternative way to configure Router 1 is shown below:

Router 1 Configuration


ip cef distributed                        !Assumes R1 supports distributed CEF 

mpls label protocol ldp                   !Use LDP for the default protocol

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.11 255.255.255.255

interface POS3/0/0 
ip address 34.0.0.44 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding
                                          !Use LDP (configured i/f default)

interface POS3/0/1 
ip address 45.0.0.44 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
mpls label protocol tdp                   !Use TDP for this interface 

The configuration of Router 2 also uses the interface mpls label protocol ldp command. If all of its interfaces are to use LDP, then the global mpls label protocol ldp could be used without any interface mpls label protocol commands.


Note Use of the mpls ip command on an interface triggers the transmission of discovery Hello messages for the interface.



Note When two platforms are directly connected by multiple packet links, the same label distribution protocol (LDP or TDP) must be configured for all of the packet interfaces connecting the platforms.



Note If a loopback IP address has been configured, it will be selected as the router ID component of the local LDP ID unless the loopback interface has been explicitly shut down or the mpls ldp router-id command has been used to specify that some other interface should be preferred when determining the LDP router ID. Configuring a loopback interface and IP address on each router is not a requirement for LDP; however, doing so helps ensure a stable LDP ID for the router because the state of loopback addresses does not change, except in response to explicit configuration action.



Note If you use a loopback interface, make sure that the IP address for the loopback interface is configured with a /32 network mask. In addition, make sure that the routing protocol in use is configured to advertise the corresponding /32 network.


Configuring LDP for Label-Controlled ATM Interfaces

The commands required to configure LDP for a label controlled ATM (LC-ATM) interface depend upon the type of interface in use.

There are three different types of LC-ATM interfaces:

Interface type 1—LC-ATM interfaces on a router.

Interface type 2—LC-ATM interfaces on an ATM switch that runs routing and MPLS control plane software. The Cisco 8540 is an example of such an ATM switch.

Interface type 3—LC-ATM interfaces on an ATM switch whose MPLS operation is controlled by a label switch controller (LSC). The BPX and MGX are examples of such ATM switches.

The following example illustrates the configuration of LDP for LC-ATM interfaces of types 1 and 2.

The example given here is based on the network topology shown in Figure 2, which incorporates a router and an ATM switch connected by means of an ATM link.

Configuring LDP for a router ATM interface is a two-step process:

a. Creating an MPLS subinterface for the ATM interface

b. Configuring LDP for the MPLS subinterface

Configuring LDP for an ATM interface on an ATM switch that is running routing and MPLS control plane software (LC-ATM interface type 2) is similar to configuring LDP for a packet interface.

Figure 2 Configuration of LDP for LC-ATM Interfaces

In the following sample configurations, the use of LDP is configured for the ATM link between Router 1 and Switch 1 (see Figure 2).

Router 1 Configuration:


interface POS3/0/1 
ip address 45.0.0.44 255.0.0.0 
mpls ip                                   !Enable hop-by-hop MPLS forwarding 
mpls label protocol tdp                   !Use TDP for this interface 


ip cef distributed                        !Assumes R1 supports distributed CEF 

interface Loopback0
 ip address 133.0.0.33 255.255.255.255

interface ATM3/0.1 mpls                   !Create the MPLS sub-interface
 ip unnumbered Loopback0                  !Use IP address of loopback
                                          !interface 0 for this interface
mpls ip                                   !Enable hop-by-hop MPLS forwarding
mpls label protocol ldp                   !Use LDP for this interface

Switch 1 Configuration:


interface Loopback0
 ip address 121.0.0.21 255.255.255.255 

interface ATM1/1/1
 ip unnumbered Loopback0                  !Use IP address of loopback
                                          !interface 0 for this interface
mpls ip                                   !Enable hop-by-hop MPLS forwarding
mpls label protocol ldp                   !Use LDP for this interface

Note The use of unnumbered interfaces is not required for LDP, but it is recommended.


Configuring LDP for Targeted Sessions

Some situations require a label distribution session between platforms that are not directly connected. For example, when you issue the mpls ip command on an MPLS traffic engineering tunnel interface, a label distribution session must be established between the tunnel head end and the tail end platforms. Such a session is called a targeted session.

Session establishment for targeted sessions is supported by targeted Hello messages sent between the platforms. Normally the transmission of targeted Hello messages is triggered by some configuration action for the application that requires the targeted session. For example, using the mpls ip command on an MPLS traffic engineering tunnel initiates the transmission of targeted Hello messages from the tunnel head end platform to the tunnel tail end platform.

Unlike LDP sessions for directly connected peers, targeted sessions are asymmetrical. One peer initiates the session by transmitting targeted Hello messages that carry a "send targeted Hello messages in response" request. This request causes the target peer to respond with targeted Hello messages if its configuration permits it to do so.

The exchange of targeted Hello messages between two nondirectly connected neighbors, N1 and N2, may occur in the following ways:

N1 may initiate the transmission of targeted Hello messages carrying a response request to N2, and N2 may send targeted Hello messages in response if its configuration permits. In this situation, N1 is considered to be active and N2 is considered to be passive.

N1 and N2 may both be configured to initiate the transmission of targeted Hello messages to each other. In this situation, both are considered to be active. Both, one, or neither N1 nor N2 can also be passive, depending on whether they have been configured to respond to requests for targeted Hello messages from each other.

The default behavior of an LSR is to ignore requests from other LSRs to send targeted Hello messages. You can configure an LSR to respond to requests for targeted Hello messages by issuing the mpls ldp discovery targeted-hellos accept command.

The protocol used for a targeted session is controlled by the active LSR in the following sense: a passive LSR that is permitted to respond to requests from an active LSR will do so using the protocol of the received targeted Hello messages.

For applications in which targeted sessions are associated with interfaces, you can use the mpls label protocol global and interface configuration commands to specify the protocol for a given interface. For example, the following commands cause an LDP targeted session to be established with the tunnel tail end route:

interface Tunnel1
tunnel destination 133.0.0.33
mpls ip
mpls label protocol ldp

Tunnel1 is an MPLS traffic engineering tunnel interface.

The output of the show mpls ldp discovery command provides the following information for targeted Hello messages:

The protocol being used for each targeted LSR.

The characteristics of the discovery activity with the targeted LSR. This includes whether the local LSR is active (an initiator of targeted Hello messages that carry a response request), passive (a responder of requests for targeted Hello messages from the other LSR), or both.

Consider the following output from the show mpls ldp discovery command:

Router# show mpls ldp discovery
Local LDP Identifier:
	118.1.1.1:0
Discovery Sources:
Interfaces:
POS2/0 (ldp): xmit/recv
LDP Id: 155.0.0.55:0
Tunnel1 (ldp): Targeted -> 133.0.0.33
Targeted Hellos:
118.1.1.1 -> 133.0.0.33 (ldp): active, xmit/recv
LDP Id: 133.0.0.33:0
118.1.1.1 -> 168.7.0.16 (tdp): passive, xmit/recv
TDP Id: 168.7.0.16:0
Router#

This command output indicates that:

The local LSR (118.1.1.1) is sending LDP link Hello messages on interface POS2/0 and has discovered neighbor 155.0.0.55.

The local LSR is sending LDP targeted Hello messages associated with interface Tunnel1 to target 133.0.0.33. The LSR uses LDP for the target because the LSR was configured to do so by means of the mpls label protocol ldp command.

The local LSR is active for targeted discovery activity with 133.0.0.33; this means that the targeted Hello messages it sends to 133.0.0.33 carry a response request. This LSR is active due to the configuration of an application (mpls ip on Tunnel1, for example) that requires an LDP session with the nondirectly connected LSR 133.0.0.33.

The local LSR is not passive for the discovery activity with 133.0.0.33 because: a) the targeted Hello messages it receives from 133.0.0.33 do not carry a response request, or b) the Local LSR has not been configured to respond to such requests.

The local LSR is sending TDP directed Hello messages to the target LSR 168.7.0.16. This LSR uses TDP because the Hell messages received from the target LSR 168.7.0.16 were TDP directed Hello messages.

The local LSR is passive in discovery activity with LSR 168.7.0.16. This means that the directed Hello messages it receives from LSR 168.7.0.16 carry a response request and that the local LSR has been configured by means of the mpls ldp discovery targeted-hello accept command to respond to such requests from LSR 168.7.0.16.

The local LSR is not active in discovery activity with LSR 168.7.0.16 because no application that requires an LDP session with LSR 168.7.0.16 has been configured on the local LSR.

The following examples illustrate the configuration of platforms for targeted sessions using the sample network shown in Figure 3. Note that Routers 1, 4, 5, and 6 in this sample network are not directly connected to each other.

Figure 3 Sample Network for Configuring LDP for Targeted Sessions

The configuration examples presented below accomplish the following:

a. Use of LDP for targeted sessions between Router 1 and Router 4. The configurations below require that Router 1 and Router 4 both be active.

b. Use of LDP for targeted sessions between Router 1 and Router 6. The configurations below require that Router 1 be active and allow Router 6 to be passive.

c. Use of TDP (the default) for targeted sessions between Router 1 and platforms other than Routers 4 and 6 (for example, between Router 1 and Router 5). The configuration for Router 5 requires it to be active in such sessions.

These examples assume that the active ends of the targeted sessions are associated with tunnel interfaces, such as MPLS traffic engineering tunnels. They show only the commands related to configuring the use of LDP targeted sessions. The examples do not show configuration of the applications that initiate the targeted sessions.

Router 1 Configuration


ip cef distributed                        !Assumes Router1 supports distributed CEF 

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.11 255.255.255.255	

interface Tunnel14                        !Tunnel to Router 4 requires label dist 
tunnel destination 131.11.0.4             !Tunnel endpoint is Router 4
mpls label protocol ldp                   !Use LDP for session with Router 4
...                                       !Other configuration for Tunnel14

interface Tunnel15                        !Tunnel to Router 5 requires label dist 
tunnel destination 131.11.0.5             !Tunnel endpoint is Router 5
...                                       !Other configuration for Tunnel15

interface Tunnel16                        !Tunnel to Router 6 requires label dist 
tunnel destination 131.11.0.5             !Tunnel endpoint is Router 6
mpls label protocol ldp                   !Use LDP for session with Router 6
...                                       !Other configuration for Tunnel16

For Router 1, the default label protocol for interfaces is TDP because there is no global mpls label protocol ldp command. This requires that the configuration for tunnel interfaces Tunnel14 and Tunnel16 include mpls label protocol ldp commands to specify use of LDP for targeted sessions associated with these interfaces. Since TDP is desired for the targeted session with Router 5, there is no need to include an mpls label protocol tdp command as part of the Tunnel15 configuration because the default protocol for interfaces on Router 1 is TDP.

Router 4 Configuration


ip cef distributed                        !Assumes Router 4 supports distributed CEF 

mpls label protocol ldp                   !Use LDP as default for all interfaces

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.44 255.255.255.255	

interface Tunnel41                        !Tunnel to Router 1 requires label dist 
tunnel destination 131.11.0.1             !Tunnel endpoint is Router 1
...                                       !Other configuration for Tunnel41

For Router 4, the global mpls label protocol ldp command makes it unnecessary to explicitly specify LDP as part of the configuration for the Tunnel41 targeted session with Router 1.

Router 5 Configuration


ip cef	                                  !Assumes Router 5 doesn't support dCEF

interface Loopback0                       !Loopback interface for LDP ID.
ip address 131.25.0.55 255.255.255.255

interface Tunnel51                        !Tunnel to Router 1 requires label dist 
tunnel destination 131.11.0.1             !Tunnel endpoint is Router 1
...                                       !Other configuration for Tunnel51

Router 5 must use TDP for all targeted sessions it participates in as an active router because its configuration contains neither the global mpls label protocol ldp command nor the interface mpls label protocol ldp command.

Router 6 Configuration


ip cef distributed	                  !Assumes Router 6 supports dCEF 

interface Loopback0	                  !Loopback interface for LDP ID.
ip address 131.25.0.66 255.255.255.255	

mpls ldp discovery targeted-hellos accept from LDP_SOURCES
                                          !Respond to requests for targeted hellos
                                          !from sources permitted by acl LDP_SOURCES

ip access-list standard LDP_SOURCES       !Define acl for targeted hello sources.
permit 131.11.0.1                         !Accept targeted hello request from Router 1.
deny any                                  !Deny requests from other sources.

By default, a router cannot be a passive neighbor in targeted sessions. Therefore, Router 1, Router 4, and Router 5 can only be active neighbors in any targeted sessions they are part of because their configuration does not permit them to be passive. The mpls ldp discovery targeted-hello accept command permits Router 6 to be a passive target in targeted sessions with Router 1. Router 6 can also be an active neighbor in targeted sessions, although the example does not include such a configuration.

Transitioning a Network from TDP to LDP

The software for this release facilitates the orderly transition of a network that uses TDP to one that uses LDP. Key software features supporting this transition to LDP include the following:

LDP and TDP are both supported and can operate simultaneously on a given platform.

The protocol to be used for directly connected peers is configurable on a per-interface basis.

The protocol to be used for nondirectly connected peers is configurable on a per-session basis.

A label-switched path (LSP) across an MPLS network can be signaled by LDP on some hops and by TDP on other hops.

These software features enable a staged transition from TDP to LDP on a link-by-link or a targeted session-by-session basis.

In considering the steps involved in configuring the simple network shown in Figure 4 to use LDP, assume that the following conditions apply:

TDP is currently used for label distribution throughout the network.

Each link has been enabled by means of the tag-switching ip command.

Tag/label distribution sessions are required between the following nondirectly connected platforms:

Router 1 (active via Tunnel15) and Router 5 (active via Tunnel51)

Router 1 (active via Tunnel16) and Router 6 (passive)

Figure 4 Sample Network for Transitioning from TDP to LDP

To accomplish the transition from TDP to LDP for the network topology shown in Figure 4, perform the following steps:


Step 1 Convert the label distribution for Link 1 from TDP to LDP by invoking the mpls label protocol ldp command on Router 1 and Router 2 for their interfaces to Link 1.

Verify proper MPLS operation.

Step 2 Convert the label distribution between Router 1 and Router 3 for the Ethernet link from TDP to LDP by invoking the mpls label protocol both command on Router 1 and Router 3 for their interfaces to Link 3.

The mpls label protocol both command enables Router 1 and Router 3 to use LDP or TDP for label distribution sessions with neighbors directly connected to Link 3 (with a preference for LDP). The resulting configuration establishes:

An LDP session between Router 1 and Router 3

A TDP session between Router 1 and Router 4

A TDP session between Router 3 and Router 4

Verify proper MPLS operation.

Step 3 Convert the label distribution for Link 2 from TDP to LDP by invoking the mpls label protocol ldp command on Router 2 and Router 3 for their interfaces to Link 2.

Verify proper MPLS operation.

Step 4 Convert the label distribution for Link 4 and Link 5 from TDP to LDP by invoking the mpls label protocol ldp command on Router 3, Router 4, and Router 5 for the interfaces to Link 4 and Link 5.

Verify proper MPLS operation. You can do so in two separate steps, if desired—one for Link 4 and one for Link 5.

Step 5 Convert the label distribution for Link 6 and Link 7 from TDP to LDP by invoking the mpls label protocol ldp command on Router 2, Router 5, and Router 6 for the interfaces to Link 6 and Link 7.

Verify proper MPLS operation. You can do so in two separate steps, if desired—one for Link 6 and one for Link 7.

Step 6 Complete the conversion for Link 3 started in Step 2 by invoking the mpls label protocol ldp command on Router 4 for Link 3, and also on Router 1 and Router 3 for Link 3.

Verify proper MPLS operation.


Note The mpls label protocol both command in Step 2 enables both LDP and TDP discovery to occur for Router 1 and Router 3 on Link 3. Since TDP is no longer required by any of the routers connected to Link 3, replacing that command with the mpls label protocol ldp command disables TDP discovery on Router 1 and Router 3, leaving only LDP discovery enabled on Router 1, Router 3, and Router 4.


Step 7 Convert the targeted label distribution between Router 1 and Router 5 from TDP to LDP.

To do so, add the mpls label protocol ldp command to the configuration of Tunnel15 on Router 1. This assumes that Router 5, which is passive for targeted sessions between Router 1 and Router 5, has previously been configured to accept targeted Hello messages from Router 1 via the mpls ldp discovery targeted-hello accept command.

Verify proper MPLS operation.

Step 8 Convert the targeted label distribution between Router 1 and Router 6 from TDP to LDP by adding the mpls label protocol ldp command to the configurations of Tunnel16 on Router 1 and Tunnel61 Router 6.

Verify proper MPLS operation.

This step completes the transition of the network from TDP to LDP.

At this point, you could make the following additional changes to "clean up" each of the configurations:

a. Add the global mpls label protocol ldp command to each configuration.

b. Remove all interface mpls label protocol ldp commands from each configuration.


CLI Command Summary

The CLI commands described in this document fall into three categories:

CLI commands introduced initially in Cisco IOS 12.0(10)ST and 12.0(14)ST) for new LDP functionality (see Table 1)—These commands support new MPLS LDP functionality and are not derived from any existing TDP commands.

Functionally equivalent, but syntactically different, LDP commands (see Table 2)—These commands, although derived from existing TDP commands, have a command syntax that differs in some respects from their corresponding TDP counterparts. For example, some commands in this category incorporate new keywords or parameters that are specific to MPLS LDP functionality.

Functionally and syntactically equivalent LDP commands (see Table 3)—These commands were not only derived from existing TDP commands, but they also preserve the basic syntax of their TDP counterparts in implementing new MPLS LDP functionality.

Table 1 New CLI Commands Being Introduced in this Release for LDP Functionality 

Command
Description

mpls label protocol (global configuration)

Specifies the default label distribution protocol for the platform.

mpls label protocol (interface configuration)

Specifies the label distribution protocol to be used on a given interface.

mpls ldp address-message

Specifies advertisement of platform addresses to a label-controlled ATM (LC-ATM) LDP peer.

mpls ldp advertise-labels old-style

Causes the interpretation of the for prefix-access-list for mpls ldp advertise-labels commands to be interpreted according to the method used in earlier software versions.

mpls ldp backoff

Configures parameters for the LDP backoff mechanism.

mpls ldp discovery transport-address

Specifies the transport address advertised in LDP Discovery Hello messages sent on an interface.

mpls ldp explicit-null

Causes a router to advertise an Explicit Null label in situations where it would normally advertise an Implicit Null label.

mpls ldp loop-detection

Enables the LDP optional loop detection mechanism.

mpls ldp neighbor

Configures a password key for use with the TCP Message Digest 5 (MD5) Signature Option for the session TCP connection with the specified neighbor.

mpls ldp router-id

Specifies a preferred interface for determining the LDP router ID.

show mpls atm-ldp bindings

Configures the use of LDP for "targeted" sessions.

show mpls ip binding

Displays information about label bindings learned by LDP.

show mpls ldp backoff

Displays information about the configured session setup backoff parameters and any potential LDP peers with which session setup attempts are being throttled.


Table 2 LDP Commands with Syntactic Structure Different from Corresponding TDP Commands 

LDP Command
Corresponding TDP Command
Description

mpls ldp advertise-labels

tag-switching advertise-tags

Controls the distribution of locally-assigned (incoming) labels by means of LDP.

mpls ldp atm control-mode

tag-switching atm allocation-mode

Controls the mode used for handling label binding requests on LC-ATM interfaces.

mpls ldp atm vc-merge

tag-switching atm vc-merge

Controls whether the vc-merge (multipoint-to-point) capability is supported for unicast label VCs.

mpls ldp maxhops

tag-switching atm maxhops

Limits the number of hops permitted in an LSP established by the Downstream on Demand method of label distribution.

debug mpls ldp advertisements

debug tag-switching tdp advertisements

Incorporates two new keywords/parameters; displays information about the advertisement of labels and interface addresses to LDP peers.

debug mpls ldp bindings

debug tag-switching tdp bindings

Displays information about addresses and label bindings learned from LDP peers by means of LDP Downstream Unsolicited label distribution. Command incorporates two new keywords/parameters.

debug mpls ldp messages

debug tag-switching tdp pies sent

Displays specific information (such as message type, source, and destination) regarding LDP messages sent to and received from LDP peers. Command incorporates several new keywords/parameters.

debug mpls ldp session io

debug tag-switching tdp pies received

Displays the contents of LDP messages sent to and received from LDP peers. Command incorporates two new keywords/parameters.

debug mpls ldp session state-machine

debug tag-switching tdp session state-machine

Incorporates one new keyword/parameter; displays information about state transitions for LDP sessions.

debug mpls ldp transport connections

debug tag-switching tdp transport connections

Incorporates two new keywords/parameters; displays information about the TCP connections used to support LDP sessions.

debug mpls ldp transport events

debug tag-switching tdp transport events

Displays information about events related to the LDP peer discovery mechanism. Command incorporates two new keywords/parameters.


Table 3 LDP Commands with Same Syntactic Structure as Corresponding TDP Commands 

LDP Command
Corresponding TDP Command
Description

mpls ip (global configuration)

tag-switching ip (global configuration)

Enables MPLS forwarding of IPv4 packets along normally routed paths for the platform.

mpls ip (interface configuration)

tag-switching ip (interface configuration)

Enables MPLS forwarding of IPv4 packets along normally routed paths for a particular interface.

mpls ldp discovery

tag-switching tdp discovery

Configures the interval between transmission of consecutive LDP discovery Hello messages, or the hold time for a discovered LDP neighbor, or the neighbors from which requests for targeted Hello messages may be honored.

mpls ldp holdtime

tag-switching tdp holdtime

Changes the time for which an LDP session is maintained in the absence of LDP messages from the session peer.

show mpls atm-ldp bindings

show tag-switching atm-tdp bindings

Displays specified entries from the ATM LDP label binding database.

show mpls atm-ldp capability

show tag-switching atm-tdp capability

Displays the ATM MPLS capabilities negotiated with LDP neighbors for LC-ATM interfaces.

show mpls interfaces

show tag-switching interfaces

Displays information about one or more interfaces that have been configured for label switching.

show mpls ldp bindings

show tag-switching tdp bindings

Displays the contents of the label information base (LIB).

show mpls ldp discovery

show tag-switching tdp discovery

Displays the status of the LDP discovery process.

show mpls ldp neighbor

show tag-switching tdp neighbor

Displays the status of LDP sessions.

show mpls ldp parameters

show tag-switching tdp parameters

Displays current LDP parameters.

debug mpls atm-ldp api

debug tag-switching atm-tdp api

Display information about the VCI allocation of label VCs (LVCs), label-free requests, and cross-connect requests.

debug mpls atm-ldp routes

debug tag-switching atm-tdp routes

Displays information about the state of the routes for which VCI requests are being made.

debug mpls atm-ldp states

debug tag-switching atm-tdp states

Displays information about LVC state transitions as they occur.

debug mpls ldp peer state-machine

debug tag-switching tdp peer state-machine

Displays information about state transitions for LDP sessions.

debug mpls ldp targeted-neighbors

debug tag-switching tdp directed-neighbors

Displays information about the target neighbor mechanism.


Command Reference

This section describes the following MPLS debugging, configuration, and display commands:

debug mpls atm-ldp api

debug mpls atm-ldp failure

debug mpls atm-ldp routes

debug mpls atm-ldp states

debug mpls ldp advertisements

debug mpls ldp backoff

debug mpls ldp bindings

debug mpls ldp messages

debug mpls ldp peer state-machine

debug mpls ldp prev-label

debug mpls ldp session io

debug mpls ldp session state-machine

debug mpls ldp targeted-neighbors

debug mpls ldp transport connections

debug mpls ldp transport events

mpls ip (global configuration)

mpls ip (interface configuration)

mpls label protocol (global configuration)

mpls label protocol (interface configuration)

mpls ldp address-message

mpls ldp advertise-labels

mpls ldp advertise-labels old-style

mpls ldp atm control-mode

mpls ldp atm vc-merge

mpls ldp backoff

mpls ldp discovery

mpls ldp discovery transport-address

mpls ldp explicit-null

mpls ldp holdtime

mpls ldp loop-detection

mpls ldp maxhops

mpls ldp neighbor

mpls ldp router-id

show mpls atm-ldp bindings

show mpls atm-ldp bindwait

show mpls atm-ldp capability

show mpls atm-ldp summary

show mpls interfaces

show mpls ip binding

show mpls ldp backoff

show mpls ldp bindings

show mpls ldp discovery

show mpls ldp neighbor

show mpls ldp parameters

debug mpls atm-ldp api

To display information about the VCI allocation of label VCs (LVCs), label-free requests, and cross-connect requests, use the debug mpls atm-ldp api command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls atm-ldp api

no debug mpls atm-ldp api

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.1(2)T

This command was modified.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use the debug mpls atm-ldp api command in conjunction with the debug mpls atm-ldp routes and debug mpls atm-ldp states command to display more complete information about an LVC.

Examples

The following shows sample output from the debug mpls atm-ldp api command:

Router# debug mpls atm-ldp api

Tailend Router Free label Req 167.50.0.0 on ATM0/0.2 VPI/VCI 1/674
 TAGATM_API: received label free request
             interface: ATM0/0.2  dir: in  vpi: 1  vci: 674
 TAGATM_API: completed label free
             interface: ATM0/0.2  vpi: 1  vci: 674
             result: TAGATM_OK

Table 4 describes the significant fields shown in the display above.

Table 4 debug mpls atm-ldp api Command Field Descriptions  

Field
Description
TAGATM_API

The subsystem that displays the message.

interface

The interface used by the driver to allocate or free VPI/VCI resources.

dir

The direction of the VC:

In—Input or receive VC

Out—Output VC

vpi

Virtual path identifier.

vci

Virtual channel identifier.

result

The return error code from the driver API.


Related Commands

Command
Description

debug mpls atm-ldp states

Displays information about LVC state transitions as they occur.


debug mpls atm-ldp failure

To display failure information about the LC-ATM, use the debug mpls atm-ldp failure command in privileged EXEC mode. Use the no form of the command to disable this feature.

debug mpls atm-ldp failure

no debug mpls atm-ldp failure

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(8)T

This command was introduced.

12.0(21)ST

The command was integrated in to Cisco IOS 12.0(21)ST.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use the debug mpls atm-ldp failure command to display failure information about the LC-ATM. This command is useful for determining failure cases. This command displays only failure information, unlike the debug mpls atm-ldp api command, which displays all API events.

Examples

The following shows sample output from the debug mpls atm-ldp failure command:

The following failure message displays during a race condition where the LC-ATM attempts to allocate LVCs on an interface where MPLS has been disabled.

Router# debug mpls atm-ldp failure

TAGATM_API_FAILURE: allocate_tag_req on ATM1/0/0 tagsw not enabled 

The following failure message displays when the LC-ATM fails to deallocate the output leg LVC of a cross connect.

Router# debug mpls atm-ldp failure

TAGATM_API_FAILURE: connDeAllocateHalfLeg returned false interface: ATM1/0/0 
vpi: 1  vci: 48 

The following failure message displays when a cross connect cannot be installed on the 
switching fabric. The result code is also provided. 

Router# debug mpls atm-ldp failure

TAGATM_API_FAILURE: setup_xconn_req InstallSvcXconn failed result 

The following message displays when attempts to establish a cross connect fail. The result describes the reason for the failure.

Router# debug mpls atm-ldp failure

TCATM-4-XCONNECT_FAILED: 10.254.13.237/32 for ATM0/1/2 ATM1/0/0 
TAGATM_API: x-conn setup request completed 
             input interface: ATM0/1/2  vpi: 1  vci: 48 
            output interface: ATM1/0/0  vpi: 2  vci: 2038 
            result = TAGATM_FAIL 
Xconnect setup response for 10.254.13.215: failure, 8 

The following message displays when attempts to remove a cross connect fail. The result describes why the cross connect cannot be removed.

Router# debug mpls atm-ldp failure

TCATM-4-XCONNECT_REMOVE_FAILED: Remove XConnect API failed for ATM1/0/12 1/894
-> ATM1/0/13 1/528 
TAGATM_API: x-conn remove request completed 
             input interface: ATM1/0/12  vpi: 1  vci: 894 
            output interface: ATM1/0/13  vpi: 1  vci: 528 
            result = TAGATM_FAIL 

Related Commands

Command
Description

debug mpls atm-ldp api

Displays all driver API events.


debug mpls atm-ldp routes

To display information about the state of the routes for which VCI requests are being made, use the debug mpls atm-ldp routes command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls atm-ldp routes

no debug mpls atm-ldp routes

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Command
Modification

11.1CT

This command was introduced.

12.1(2)T

This command was modified.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When there are many routes and system activities (that is, shutting down interfaces, learning new routes, and so forth), the debug mpls atm-ldp routes command displays extensive information that might interfere with system timing. Most commonly, this interference affects normal LDP operation. To avoid this problem, you can increase the LDP hold time by means of the mpls ldp holdtime command.

Examples

The following shows sample output from the debug mpls atm-ldp routes command:

Router# debug mpls atm-ldp routes

CleanupRoutes,not deleting route of idb ATM0/0.2,rdbIndex 0
tcatmFindRouteTags,153.7.0.0/16,idb=ATM0/0.2,nh=134.111.102.98,index=0
AddNewRoute,153.7.0.0/16,idb=ATM0/0.2
CleanupRoutes,153.7.0.0/16
CleanupRoutes,not deleting route of idb ATM0/0.2,rdbIndex 0
tcatmFindRouteTags,153.8.0.0/16,idb=ATM0/0.2,nh=134.111.102.98,index=0
AddNewRoute,153.8.0.0/16,idb=ATM0/0.2
CleanupRoutes,153.8.0.0/16
CleanupRoutes,not deleting route of idb ATM0/0.2,rdbIndex 0
tcatmFindRouteTags,153.9.0.0/16,idb=ATM0/0.2,nh=134.111.102.98,index=0
AddNewRoute,153.9.0.0/16,idb=ATM0/0.2
CleanupRoutes,153.9.0.0/16
CleanupRoutes,not deleting route of idb ATM0/0.2,rdbIndex 0
tcatmFindRouteTags,153.10.0.0/16,idb=ATM0/0.2,nh=134.111.102.98,index=0
AddNewRoute,153.10.0.0/16,idb=ATM0/0.2
CleanupRoutes,153.10.0.0/16
CleanupRoutes,not deleting route of idb ATM0/0.2,rdbIndex 0
tcatmFindRouteTags,153.11.0.0/16,idb=ATM0/0.2,nh=134.111.102.98,index=0
AddNewRoute,153.11.0.0/16,idb=ATM0/0.2
CleanupRoutes,153.11.0.0/16

Table 5 describes the significant fields in the display above.

Table 5 debug mpls atm-ldp routes Command Field Descriptions

Field
Description
CleanupRoutes

Cleans up the routing table after a route has been deleted.

not deleting route of 
idb ATM0/0.2

The route cleanup event has not removed the specified route.

rdbIndex

Index identifying the route.

tcatmFindRouteTags

Request a VC for the route.

idb

The internal descriptor for an interface.

nh

Next hop for the route.

index

Identifier for the route.

AddNewRoute

Action of adding routes for a prefix or address.


Related Commands

Command
Description

mpls ldp holdtime

Changes the time an LDP session will be maintained in the absence of LDP messages from the session peer.


debug mpls atm-ldp states

To display information about LVC state transitions as they occur, use the debug mpls atm-ldp states command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls atm-ldp states

no debug mpls atm-ldp states

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.1(2)T

This command was modified.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When there are many routes and system activities (such as shutting down interfaces, learning new routes, and so forth), the debug mpls atm-ldp states command outputs extensive information that might interfere with system timing. Most commonly, this interference affects normal LDP operation. To avoid this problem, you should increase the LDP hold time by means of the mpls ldp holdtime command.

Examples

The following shows sample output from the debug mpls atm-ldp states command:

Router# debug mpls atm-ldp states

Transit Output 166.35.0.0 VPI/VCI 1/67 Active -> XmitRelease NoPath
Transit Input 166.35.0.0 VPI/VCI 1/466 Active -> ApiWaitParentLoss ParentLoss
Transit Input 166.35.0.0 VPI/VCI 1/466 ApiWaitParentLoss -> ParentWait ApiSuccess
Transit Input 166.35.0.0 VPI/VCI 1/466 ParentWait -> XmitWithdraw NoPath
Transit Input 166.35.0.0 VPI/VCI 1/466 XmitWithdraw -> XmitWithdraw Transmit
Transit Input 166.35.0.0 VPI/VCI 1/466 XmitWithdraw -> NonExistent Release
Transit Input 166.35.0.0 VPI/VCI 1/466 NonExistent -> NonExistent ApiSuccess

Table 6 describes the significant fields shown in the sample display above.

Table 6 debug mpls atm-ldp states Command Field Descriptions

Field
Description
Transit Output

Output side of a label virtual circuit (LVC).

VPI/VCI

VC value.

Transit Input

Input side of an LVC.


Related Commands

Command
Description

mpls ldp holdtime

Changes the time an LDP session is maintained in the absence of LDP messages from the session peer.


debug mpls ldp advertisements

To display information about the advertisement of labels and interface addresses to LDP peers, use the debug mpls ldp advertisements command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp advertisements [peer-acl acl] [prefix-acl acl]

no debug mpls ldp advertisements [peer-acl acl] [prefix-acl acl]

Syntax Description

peer-acl acl

(Optional) Limits the displayed advertisements to those for LDP peers permitted by the access control list (acl).

prefix-acl acl

(Optional) Limits the displayed advertisements to those for prefixes permitted by the access control list (acl).


Defaults

Displays information about advertisements to all LDP peers for all prefixes.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to monitor the label and address advertisements to LDP peers.

Use the peer-acl or prefix-acl options separately or together to limit the information display to specific LDP peers and/or specific prefixes.


Note This command monitors advertisement of non-LC-ATM labels (generic labels) only. Use the debug mpls atm-ldp command to monitor LC-ATM activity.


Examples

The following shows sample output from the debug mpls ldp advertisements command:

Router# debug mpls ldp advertisements

tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 130.77.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 133.0.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 34.0.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 103.0.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 35.0.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 38.0.0.33
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 34.0.0.0/8, label 3 (#2)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 203.0.7.7/32, label 24 (#4)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 35.0.0.0/8, label 3 (#8)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 103.0.0.0/8, label 3 (#10)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 138.1.0.0/16, label 26 (#14)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 155.0.0.55/32, label 27 (#16)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 38.0.0.0/8, label 3 (#18)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 212.10.1.0/24, label 30 (#24)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 59.0.0.0/8, label 32 (#28)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 144.0.0.44/32, label 33 (#30)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 106.0.0.0/8, label 34 (#32)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 133.0.0.33/32, label 3 (#34)
tagcon: peer 144.0.0.44:0 (pp 0x60E105BC): advertise 45.0.0.0/8, label 39 (#36)

Table 7 describes the significant fields shown in the sample display above.

Table 7 debug mpls ldp advertisements Command Field Descriptions  

Field
Description
tagcon:

Identifies the source of the message as the label control subsystem.

peer a.b.c.d:e 

The LDP identifier of the peer to which the advertisement was targeted.

(pp 0xnnnnnnnn)

The identifier for the data structure used to represent the peer at the label distribution level. Useful for correlating debug output.

advertise X

Identifies what was advertised to the peer—either an interface address ("a.b.c.d") or label binding ("a.b.c.d/m, label t (#n)").

(#n) 

For a label binding advertisement, the sequence number of the label information base (LIB) modification that made it necessary to advertise the label.


Related Commands

Command
Description

show mpls ldp neighbor

Displays the status of LDP sessions.

show mpls ip binding

Displays label bindings known to the LSR.

debug mpls ldp bindings

Displays information about changes to the LIB used to keep track of label bindings learned from LDP peers through LDP downstream label distribution.


debug mpls ldp backoff

To display information about the LDP backoff mechanism parameters, use the debug mpls ldp backoff command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp backoff

no debug mpls ldp backoff

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to monitor backoff parameters configured for LDP sessions.

Examples

The following shows sample output from the debug mpls ldp backoff command.

Router# debug mpls ldp backoff 

LDP session establishment backoff debugging is on 
Router# 
Jan 6 22:31:13.012: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/6 
Jan 6 22:31:13.824: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/6 
Jan 6 22:31:17.848: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/6 
Jan 6 22:31:18.220: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/6 
Jan 6 22:31:21.908: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/6 
Jan 6 22:31:22.980: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/6 
Jan 6 22:31:25.724: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/7 
Jan 6 22:31:26.944: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/7 
Jan 6 22:31:30.140: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/7 
Jan 6 22:31:31.932: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/7 
Jan 6 22:31:35.028: ldp: Backoff peer ok: 12.12.12.12:0; backing off; threshold/count 8/7 
Jan 6 22:31:35.788: ldp: Backoff peer ok: 12.12.12.12:1; backing off; threshold/count 8/7 
Jan 6 22:31:39.332: ldp: Update backoff rec: 12.12.12.12:0, threshold = 8, tbl ents 2 
Jan 6 22:31:39.640: ldp: Update backoff rec: 12.12.12.12:1, threshold = 8, tbl ents 2 

Table 8 describes the significant fields in the sample display shown above.

Table 8 debug mpls ldp backoff Command Field Descriptions 

Field
Description
ldp

Identifies the Label Distribution Protocol.

Backoff peer ok: 
a.b.c.d:n

Identifies the LDP peer for which a session is being delayed because of a failure to establish a session due to incompatible configuration.

backing off;

Indicates that a session setup attempt failed and the LSR is delaying its next attempt (that is, is backing off).

threshold/count x/y

Identifies a set threshold (x) and a count (y) that represents the time that has past since the last attempt to set up a session with the peer. The count is incremented every 15 seconds until it reaches the threshold. When the count equals the threshold, a fresh attempt is made to set up an LDP session with the peer.

Update backoff rec

Indicates that the backoff period is over and that it is time for another attempt to set up an LDP session.

threshold = x

Indicates the backoff time of x*15 seconds, for the next LDP session attempt with the peer.

tbl ents 2

Indicate unsuccessful attempts to set up an LDP session with two different LDP peers. In this example, attempts to set up sessions with LDP peers 12.12.12.12:0 and 12.12.12.12:1 are failing.


Related Commands

Command
Description

mpls ldp backoff

Configures session setup delay parameters for the LDP backoff mechanism.

show mpls ldp backoff

Displays information about the configured session setup backoff parameters and any potential LDP peers with which session setup attempts are being throttled.


debug mpls ldp bindings

To display information about addresses and label bindings learned from LDP peers by means of LDP downstream unsolicited label distribution, use the debug mpls ldp bindings command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp bindings [peer-acl acl] [prefix-acl acl]

no debug mpls ldp bindings [peer-acl acl] [prefix-acl acl]

Syntax Description

peer-acl acl

(Optional) Limits the displayed binding information to that learned from LDP peers permitted by the access control list (acl).

prefix-acl acl

(Optional) Limits the displayed binding information to that learned for prefixes permitted by the access control list (acl).


Defaults

Displays information about all bindings learned from all LDP peers.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to monitor label bindings and LSR addresses learned from LDP peers.


Note This command monitors non-LC-ATM labels (generic labels) only. Use the debug mpls atm-ldp command to monitor LC-ATM activity.


Examples

The following shows sample output from the debug mpls ldp bindings command:

Router# debug mpls ldp bindings

tagcon:tibent(34.0.0.0/8):created; find route tags request
tagcon:tibent(34.0.0.0/8):label 3 (#2) assigned
tagcon:tibent(203.0.7.7/32):created; find route tags request
tagcon:tibent(203.0.7.7/32):label 24 (#4) assigned
tagcon:tibent(144.0.0.44/32):created; find route tags request
tagcon:tibent(144.0.0.44/32):label 33 (#30) assigned
tagcon:tibent(106.0.0.0/8):created; find route tags request
tagcon:tibent(106.0.0.0/8):label 34 (#32) assigned
tagcon:tibent(133.0.0.33/32):created; find route tags request
tagcon:tibent(133.0.0.33/32):label 3 (#34) assigned
tagcon:tibent(45.0.0.0/8):created; find route tags request
tagcon:tibent(45.0.0.0/8):label 39 (#36) assigned
tagcon:Assign peer id; 144.0.0.44:0:id 0
tagcon:144.0.0.44:0:144.0.0.44 added to addr<->ldp ident map
tagcon:144.0.0.44:0:34.0.0.44 added to addr<->ldp ident map
tagcon:144.0.0.44:0:45.0.0.44 added to addr<->ldp ident map
tagcon:tibent(144.0.0.44/32):rem label 3 from 144.0.0.44:0 added
tagcon:tibent(34.0.0.0/8):label 3 from 144.0.0.44:0 added
tagcon:tibent(45.0.0.0/8):label 3 from 144.0.0.44:0 added
tagcon:tibent(107.0.0.0/8):created; remote label learned
tagcon:tibent(107.0.0.0/8):label 55 from 144.0.0.44:0 added
tagcon:tibent(203.0.7.7/32):label 209 from 144.0.0.44:0 added
tagcon:tibent(133.0.0.33/32):label 207 from 144.0.0.44:0 added

Table 9 describes the significant fields shown in the sample display above.

Table 9 debug mpls ldp bindings Command Field Descriptions  

Field
Description
tagcon:

Identifies the source of the message as the label control subsystem.

tibent(network/mask)

The destination that has a label binding change.

created; reason

A LIB entry has been created for the specified destination for the indicated reason.

rem label ... 

Describes a change to the label bindings for the specified destination. The change is for a label binding learned from the specified LDP peer.

lcl label ...

Describes a change to a locally assigned (incoming) label for the specified destination.

(#n) 

The sequence number of the modification to the LIB corresponding to the local label change.

a.b.c.d:n: e.f.g.h 
added to addr<->ldp 
ident map

The address e.f.g.h has been added to the set of addresses associated with LDP identifier a.b.c.d:n.


Related Commands

Command
Description

show mpls ldp bindings

Displays the contents of the label information base (LIB).


debug mpls ldp messages

To display specific information (such as message type, source, and destination) regarding LDP messages sent to and received from LDP peers, use the debug mpls ldp messages command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp messages {sent | received} [all] [peer-acl acl]

no debug mpls ldp messages {sent | received} [all] [peer-acl acl]

Syntax Description

sent

Displays LDP messages sent to LDP peers permitted by the access control list (acl).

received

Displays LDP messages received from LDP peers permitted by the access control list (acl).

all

(Optional) Displays all LDP messages sent to and received from LDP peers (including periodic KeepAlive messages) permitted by the access control list (acl).

peer-acl acl

(Optional) Limits the messages displayed for LDP peers in accordance with the access control list (acl).


Defaults

All messages sent (for sent keyword) or received (for received keyword) are displayed except for periodic KeepAlive messages

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

LDP requires periodic transmission of KeepAlive messages. If you do not specify the all option, periodic KeepAlive messages are not displayed.

Examples

The following shows sample output from the debug mpls ldp messages received command:

Router# debug mpls ldp messages received
Router# debug mpls ldp messages sent

ldp: Rcvd init msg from 144.0.0.44 (pp 0x0)
ldp: Sent init msg to 144.0.0.44:0 (pp 0x0)
ldp: Sent keepalive msg to 144.0.0.44:0 (pp 0x0)
ldp: Rcvd keepalive msg from 144.0.0.44:0 (pp 0x0)
ldp: Sent address msg to 144.0.0.44:0 (pp 0x610F00E0)
ldp: Sent label mapping msg to 144.0.0.44:0 (pp 0x610F00E0)
ldp: Sent label mapping msg to 144.0.0.44:0 (pp 0x610F00E0)
ldp: Sent label mapping msg to 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd address msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610F00E0)

Table 10 describes the significant fields shown in the sample display above.

Table 10 debug mpls ldp messages received Command Field Descriptions  

Field
Description
ldp: 

Identifies the source of the displayed information as LDP.

Rcvd xxx msg
Sent xxx msg

The type of message received or sent.

from a.b.c.d 

The host that sent the message. Used in the early stages of the opening of an LDP session, when the LDP identifier is not yet known.

from a.b.c.d:e
to a.b.c.d:e

The LDP identifier of the peer that sent the message or to which the message was sent.

(pp 0xnnnnnnnn)

Identifies the data structure used to represent the peer at the label distribution level. Useful for correlating debug output.


Related Commands

Command
Description

debug mpls ldp session io

Displays the contents of LDP messages sent to and received from LDP peers.


debug mpls ldp peer state-machine

To display information about state transitions for LDP sessions, use the debug mpls ldp peer state-machine command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp peer state-machine

no debug mpls ldp peer state-machine

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no options.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

LDP manages peer sessions by means of two coupled state machines:

A low-level state machine that deals with session establishment and shutdown

A high-level state machine that deals with setting up and shutting down label advertisement

Use the debug mpls ldp session state-machine command to monitor the lower-level session state machine.

Use the debug mpls ldp peer state-machine command to monitor the higher-level session state machine.

Examples

The following shows sample output from the debug mpls ldp peer state-machine command:

Router# debug mpls ldp peer state-machine

tagcon: start session TCP timers for 144.0.0.44:0 (pp 0x610EEC84)
tagcon: Enqueue peer up work for 144.0.0.44:0 (pp 0x610EEC84)
tagcon: peer 144.0.0.44:0 (pp 0x610EEC84): Event unsol open
    unsol op pdg -> estab
tagcon: Send initial advertisements to peer 144.0.0.44:0
tagcon: Initial address advertisement to peer 144.0.0.44:0
tagcon: Initial label advertisement to peer 144.0.0.44:0
...
tagcon: peer 144.0.0.44:0 (pp 0x610EEC84): Event down
    estab -> destroyed
tagcon: peer 144.0.0.44:0 (pp 0x610EEC84): Event cleanup done
    destroyed -> non-ex

Table 11 describes the significant fields shown in the sample display above.

Table 11 debug mpls ldp peer state-machine Command Field Descriptions

Field
Description
tagcon:

Identifies the source of the message as the label control subsystem.

a.b.c.d:e 

The LDP identifier of the peer for the session with the state change.

(pp 0xnnnnnnnn)

Address of the data structure used to represent the peer at the label distribution level. This address is useful for correlating debug output.

Event E 

The event causing the state change.

s1 -> s2 

The state of the LDP session has changed from state s1 to state s2.


Related Commands

Command
Description

show mpls ldp neighbor

Displays the status of LDP sessions.

debug mpls ldp peer state-machine

Displays information about state transitions for LDP sessions.

debug mpls ldp session io

Displays information about LDP messages sent to or received from LDP peers.


debug mpls ldp prev-label

To display debug information when a local label binding associated with a prefix is withdrawn and freed, use the debug mpls ldp prev-label command in privileged EXEC mode. To disable debugging output, use the no form of this command.

debug mpls ldp prev-label [prefix-acl acl [peer-acl acl]

no debug mpls lad prev-label [prefix-acl acl [peer-acl acl]

Syntax Description

prefix-acl acl

(Optional) Limits the displayed binding information to that allocated for prefixes permitted by a prefix access control list (ACL).

peer-acl acl

(Optional) Limits the displayed binding withdraw information to those Label Distribution Protocol (LDP) peers permitted by a peer ACL.


Command Default

Debugging of previous local label binding changes is disabled.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(21)ST

This command was introduced.

12.2(8)T

This command was integrated into Cisco IOS Release 12.2(8)T.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.


Usage Guidelines

Use this command to monitor LDP information when a local label binding associated with a prefix is withdrawn and freed. LDP withdraws a previously advertised label before advertising a new label.

If you enter the debug mpls ldp prev-label command without an optional keyword and argument, the command displays output for all previous label binding changes. Use the prefix-acl acl or peer-acl acl keywords and arguments to limit the output to prefixes defined by the respective ACLs.

Examples

The following is sample output from the debug mpls ldp prev-label command:

Router# debug mpls ldp prev-label

tagcon: Changing state to WITHDRAWN for prefix=10.0.1.1, label31
tagcon: Creating prev_lbl_info for prefix=10.0.1.1, label31
tagcon: noroute hold timer expired for 10.0.1.1/255.255.255.255, tag withdrawn, seqno 47
tagcon: tibent(10.0.1.1/32): label 32 from 10.0.0.2:0 removed
tagcon: Deleting prev label info for prefix = 10.0.1.1, tag = 31

Table 12 describes the significant fields shown in the display.

Table 12 debug mpls ldp prev-label Field Descriptions 

Field
Description

tagcon:

Identifies the source of the message as the label control subsystem.

Changing state to WITHDRAWN

Describes the label binding change; in this case, the label is to be withdrawn.

for prefix=10.0.1.1

The prefix (10.0.1.1) from which the local label binding is to be withdrawn and freed.

label31

The local label binding (31) that is to be withdrawn from the prefix.

tibent(10.0.1.1/32)

The hostname, network, and mask for the destination that has a label binding change.


Related Commands

Command
Description

debug mpls ldp bindings

Displays information about addresses and label bindings learned from LDP peers by means of LDP downstream unsolicited label distribution.


debug mpls ldp session io

To display the contents of LDP messages sent to and received from LDP peers, use the debug mpls ldp session io command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp session io [all] [peer-acl acl]

no debug mpls ldp session io [all] [peer-acl acl]

Syntax Description

all

(Optional) Includes the contents of periodic KeepAlive messages in the displayed message output to LDP peers.

peer-acl acl

(Optional) Limits the displayed message output to those LDP peers permitted by the access control list (acl).


Defaults

Displays the contents of LDP messages sent and received except for periodic KeepAlive messages.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Displays the contents of all messages sent and received except for periodic KeepAlive messages.

Examples

The following shows sample output from the debug mpls ldp session io command:

Router# debug mpls ldp session io all

ldp: Rcvd init msg from 144.0.0.44 (pp 0x0)
ldp: LDP init msg: PDU hdr: LDP Id: 144.0.0.44:0; Msg Contents:
  0x00 0x01 0x00 0x20 0x90 0x00 0x00 0x2C 0x00 0x00 0x02 0x00 0x00 0x16 0x00 0x00 
  0x10 0x21 0x05 0x00 0x00 0x0E 0x00 0x01 0x00 0xB4 0x00 0x00 0x00 0x00 0x85 0x00 
  0x00 0x21 0x00 0x00 
ldp: Sent init msg to 144.0.0.44:0 (pp 0x0)
ldp: LDP init msg: PDU hdr: LDP Id: 133.0.0.33:0; Msg Contents:
  0x00 0x01 0x00 0x20 0x85 0x00 0x00 0x21 0x00 0x00 0x02 0x00 0x00 0x16 0x00 0x00 
  0x06 0x32 0x05 0x00 0x00 0x0E 0x00 0x01 0x00 0xB4 0x00 0x00 0x00 0x00 0x90 0x00 
  0x00 0x2C 0x00 0x00 
ldp: Sent keepalive msg to 144.0.0.44:0 (pp 0x0)
ldp: LDP keepalive msg: PDU hdr: LDP Id: 133.0.0.33:0; Msg Contents:
  0x00 0x01 0x00 0x0E 0x85 0x00 0x00 0x21 0x00 0x00 0x02 0x01 0x00 0x04 0x00 0x00 
  0x06 0x33 
ldp: Rcvd keepalive msg from 144.0.0.44:0 (pp 0x0)
ldp: LDP keepalive msg: PDU hdr: LDP Id: 144.0.0.44:0; Msg Contents:
  0x00 0x01 0x00 0x0E 0x90 0x00 0x00 0x2C 0x00 0x00 0x02 0x01 0x00 0x04 0x00 0x00 
  0x10 0x22 
ldp: Sent address msg to 144.0.0.44:0 (pp 0x610ECDD0)
ldp: LDP address msg: PDU hdr: LDP Id: 133.0.0.33:0; Msg Contents:
  0x00 0x01 0x00 0x34 0x85 0x00 0x00 0x21 0x00 0x00 0x03 0x00 0x00 0x2A 0x00 0x00 
  0x06 0x34 0x01 0x01 0x00 0x22 0x00 0x01 0x02 0x00 0x00 0xA3 0x82 0x42 0x00 0x21 
  0x82 0x4D 0x00 0x21 0x85 0x00 0x00 0x21 0x22 0x00 0x00 0x21 0x67 0x00 0x00 0x21 
  0x23 0x00 0x00 0x21 0x26 0x00 0x00 0x21 
ldp: Sent label mapping msg to 144.0.0.44:0 (pp 0x610ECDD0)
ldp: LDP label mapping msg: PDU hdr: LDP Id: 133.0.0.33:0; Msg Contents:
  0x00 0x01 0x00 0x22 0x85 0x00 0x00 0x21 0x00 0x00 0x04 0x00 0x00 0x18 0x00 0x00 
  0x06 0x36 0x01 0x00 0x00 0x08 0x02 0x00 0x01 0x20 0xCB 0x00 0x07 0x07 0x02 0x00 
  0x00 0x04 0x00 0x00 0x00 0x18 
ldp: Rcvd address msg from 144.0.0.44:0 (pp 0x610ECDD0)
ldp: LDP address msg: PDU hdr: LDP Id: 144.0.0.44:0; Msg Contents:
  0x00 0x01 0x00 0x24 0x90 0x00 0x00 0x2C 0x00 0x00 0x03 0x00 0x00 0x1A 0x00 0x00 
  0x10 0x23 0x01 0x01 0x00 0x12 0x00 0x01 0x90 0x00 0x00 0x2C 0x02 0x00 0x00 0xA4 
  0x22 0x00 0x00 0x2C 0x2D 0x00 0x00 0x2C 
ldp: Rcvd label mapping msg from 144.0.0.44:0 (pp 0x610ECDD0)
ldp: LDP label mapping msg: PDU hdr: LDP Id: 144.0.0.44:0; Msg Contents:
  0x00 0x01 0x00 0x22 0x90 0x00 0x00 0x2C 0x00 0x00 0x04 0x00 0x00 0x18 0x00 0x00 
  0x10 0x24 0x01 0x00 0x00 0x08 0x02 0x00 0x01 0x20 0x90 0x00 0x00 0x2C 0x02 0x00 
  0x00 0x04 0x00 0x00 0x00 0x03 

Table 13 describes the significant fields shown in the sample display above.

Table 13 debug mpls ldp session io Command Field Descriptions 

Field
Description
ldp:

Identifies the source of the message as LDP.

Rcvd xxx msg

Indicates that a message of the specified type has been received.

from a.b.c.d

The host to which the message has been sent. Used in the early stages of the opening of an LDP session when the LDP identifier is not yet known.

Sent xxx msg 

Indicates that a message of the specified type has been sent.

to a.b.c.d

The host to which the message has been sent. Used in the early stages of the opening of an LDP session when the LDP identifier is not yet known.

to a.b.c.d:e

The LDP identifier of the peer to which the message has been sent.

(pp 0xnnnnnnnn)

Identifies the data structure used to represent the peer at the label distribution level. Useful for correlating debug output.

--LDP xxx msg

The type of message that has been sent.

PDU_hdr: LDP Id: 
a.b.c.d:e

The LDP identifier of the sender included in the LDP protocol data unit (PDU) header.

Msg contents: 0xnn 
... 0xnn

The contents of the message represented as a sequence of bytes.


Related Commands

Command
Description

debug mpls ldp session io

Displays information about LDP messages sent to or received from LDP peers.


debug mpls ldp session state-machine

To display information about state transitions for LDP sessions, use the debug mpls ldp session state-machine command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp session state-machine [peer-acl acl]

no debug mpls ldp session state-machine [peer-acl acl]

Syntax Description

peer-acl acl

(Optional) Limits the displayed information to that for LDP peers permitted by the access control list (acl).


Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

LDP manages peer sessions by means of two coupled-state machines:

A low-level state machine that deals with session establishment and shutdown

A high-level state machine that deals with setting up and shutting down label advertisement

Use the debug mpls ldp session state-machine command to monitor the lower-level session state machine.

Use the debug mpls ldp peer state-machine command to monitor the higher-level session state machine.

Examples

The following shows sample output from the debug mpls ldp session state-machine command:

Router# debug mpls ldp session state-machine

ldp: ptcl_adj:144.0.0.44(0x610EED30): Non-existent -> Role pasv
ldp: create ptcl_adj: tp = 0x610EED30, ipaddr = 144.0.0.44
ldp: ptcl_adj:144.0.0.44(0x610EED30): Event: Xport opened;
    Role pasv -> Role pasv
ldp: ptcl_adj:34.0.0.44(0x610EED30): Event: Rcv Init;
    Role pasv -> Init rcvd pasv
ldp: ptcl_adj:34.0.0.44(0x610EED30): Event: Rcv KA;
    Init rcvd pasv -> Oper
ldp: ptcl_adj:unknown(0x610EED30): Event: Xport closed;
    Oper -> Non-existent

Table 14 describes the significant fields in the sample display shown above.

Table 14 debug mpls tdp session state-machine Command Field Descriptions  

Field
Description
ldp:

Identifies the source of the message as LDP.

ptcl_adj:a.b.c.d 

Identifies the network address of the LDP peer.

(0xnnnnnnnn) 

Identifies the data structure used to represent the peer at the protocol level. Useful for correlating debug output.

Event: E 

The event that caused the state transition.

s1 -> s2 

The state of the LDP session has changed from state s1 to state s2.


Related Commands

Command
Description

debug mpls ldp peer state-machine

Monitors the high-level peer session state machine.


debug mpls ldp targeted-neighbors

To display information about the target neighbor mechanism, use the debug mpls ldp targeted-neighbors command in privileged EXEC mode. This mechanism establishes LDP adjacencies to peers that are not directly adjacent, such as peers at either end of a tunnel. To disable this feature, use the no form of the command.

debug mpls ldp targeted-neighbors

no debug mpls ldp targeted-neighbors

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Platforms that are not directly connected may engage in LDP label distribution (for example, to support two-level labeling across an LSP tunnel).

An LDP session between nondirectly connected LSRs is called a targeted session and is supported by LDP extended discovery which uses targeted Hello messages sent to specific IP addresses.

An LSR (Router 1) attempting to initiate an LDP targeted session with another LSR (Router 2) sends targeted Hello messages sent to a specific IP address of Router 2. If the configuration of Router 2 permits it to respond to targeted Hello messages from Router 1, it does so, and the LDP session can be established. In this situation, Router 1 is said to be an active LSR for the targeted session because it initiated the targeted Hello messages; Router 2 is said to be a passive LSR for the session because it responded to them.

As with LDP sessions between two directly connected LSRs, it is possible for a targeted session to be the result of multiple discovery activities which are targeted to different IP addresses for the same LSR. In addition, it is possible for both LSRs in a targeted session to be active and for both to be passive.

The debug messages enabled by debug mpls ldp targeted-neighbors report activity relating to targeted sessions.

Examples

The following shows sample output from the debug mpls ldp targeted-neighbors command:

Router# debug mpls ldp targeted-neighbors

ldp-trgtnbr: 144.0.0.44 Req active
ldp-trgtnbr: 144.0.0.44 allocated
ldp-trgtnbr: 144.0.0.44 Set peer start; flags 0x0
ldp-trgtnbr: 144.0.0.44 Defer peer cleanup; cleancnt 1
ldp-trgtnbr: 144.0.0.44 Set peer finished; flags 0xF
ldp-trgtnbr: 144.0.0.44 ref count incremented to 1
ldp-trgtnbr: 144.0.0.44 Release active; ref count decremented to 0
ldp-trgtnbr: 144.0.0.44 Clear peer start; flags 0xF
ldp-trgtnbr: 144.0.0.44 Undefer cleanup start; clearcnt 0, flags 0xC
ldp-trgtnbr: 144.0.0.44 Undefer cleanup finish; clearcnt 0, flags 0x8
ldp-trgtnbr: 144.0.0.44 Clear peer finished; flags 0x8
ldp-trgtnbr: 144.0.0.44 freed

Table 15 describes the significant fields shown in the sample display above.

Table 15 debug mpls ldp targeted-neighbors Command Field Descriptions

Field
Description
ldp-trgtnbr:

Identifies this as an LDP targeted neighbor debug statement.

144.0.0.44	

IP address for the targeted neighbor.


Related Commands

Command
Description

show mpls ldp neighbor

Displays the status of LDP protocol sessions.


debug mpls ldp transport connections

To display information about the TCP connections used to support LDP sessions, use the debug mpls ldp transport connections command in privileged EXEC mode. To disable this feature, use the no form of the command.

debug mpls ldp transport connections [peer-acl acl] [interface interface]

no debug mpls ldp transport connections [peer-acl acl] [interface interface]

Syntax Description

peer-acl acl

(Optional) Limits the displayed information to that for LDP peers permitted by the access control list (acl).

interface interface

(Optional) Limits the displayed information to that for the specified interface.


Defaults

Display information about LDP TCP connection activity for all peers and all interfaces.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to monitor LDP activity relating to the establishment of the transport (TCP) connection for LDP sessions.

When two devices establish a TCP connection for an LDP session, the device with the larger transport address plays an active role and the other plays a passive role. The active device attempts to establish a TCP connection to the well-known LDP port at the passive device. The passive device waits for the connection to the well-known port to be established.

Examples

The following shows sample output from the debug mpls ldp transport connections command:

Router# debug mpls ldp transport connections

Debug output at active peer:

ldp: Opening listen port 646 for 144.0.0.44, 34.0.0.44
ldp: Open LDP listen TCB 0x60E105BC; lport = 646; fhost = 144.0.0.44
ldp: Add listen TCB to list; tcb 0x60E105BC; addr 144.0.0.44
ldp: Incoming ldp conn 133.0.0.33:646 <-> 144.0.0.44:11042
ldp: create ptcl_adj: tp = 0x610ECD64, ipaddr = 144.0.0.44

Debug output at passive peer:

ldp: Opening ldp conn; adj 0x60BAC33C, 144.0.0.44 <-> 133.0.0.33
ldp: ldp conn is up; adj 0x60BAC33C, 144.0.0.44:11042 <-> 133.0.0.33:646

Table 16 describes the significant fields shown in the sample display shown above.

Table 16 debug mpls ldp transport connections Command Field Descriptions  

Field
Description
ldp:

Identifies the source of the message as LDP.

adj 0xnnnnnnnn 

Identifies the data structure used to represent the peer at the transport level. Useful for correlating debug output.

a.b.c.d -> p.q.r.s

Indicates a TCP connection between a.b.c.d and p.q.r.s.

a.b.c.d:x -> 
p.q.r.s:y

Indicates a TCP connection between a.b.c.d, port x and p.q.r.s, port y.


Related Commands

Command
Description

debug mpls ldp transport events

Prints information about the events related to the LDP peer discovery mechanism.


debug mpls ldp transport events

To display information about events related to the LDP peer discovery mechanism, use the debug mpls ldp transport events command in privileged EXEC mode. This mechanism is used to determine the devices with which you wish to establish LDP sessions. To disable this feature, use the no form of the command.

debug mpls ldp transport events [peer-acl acl] [interface]

no debug mpls ldp transport events [peer-acl acl] [interface]

Syntax Description

peer-acl acl

(Optional) Limits the displayed information to that for LDP peers permitted by the access control list (acl).

interface

(Optional) Limits the displayed information to that for the specified interface.


Defaults

Displays information about LDP discovery activity for all peers and all interfaces.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to monitor LDP discovery activity.

This command might generate a great deal of output. Use the peer-acl option or interface option, or both, to limit the output to peers or interfaces of interest.


Note The command includes all of the output generated by the debug mpls ldp transport connection command.


Examples

The following shows sample output from the debug mpls ldp transport events command:

Router# debug mpls ldp transport events

ldp: enabling ldp on Ethernet1/1/1
ldp: Set intf id: intf 0x611D684C, Ethernet1/1/1, not lc-atm, intf_id 0
ldp: Set intf id: intf 0x617C5638, ATM0/0.2, not lc-atm, intf_id 0
ldp: Send ldp hello; ATM3/0.1, src/dst 8.1.1.1/224.0.0.2, inst_id 1, tcatm
ldp: Rcvd ldp hello; ATM3/0.1, from 203.0.7.7 (203.0.7.7:2), intf_id 1, opt 0x8, tcatm
ldp: Send ldp hello; Ethernet1/1/1, src/dst 138.1.0.88/224.0.0.2, inst_id 0
ldp: Rcvd ldp hello; Ethernet1/1/1, from 10.105.0.9 (7.1.1.1:0), intf_id 0, opt 0xC
ldp: ldp Hello from 10.105.0.9 (7.1.1.1:0) to 224.0.0.2, opt 0xC
ldp: New adj 0x617C5EBC from 10.105.0.9 (7.1.1.1:0), Ethernet1/1/1
ldp: Opening ldp conn; adj 0x617C5EBC, 8.1.1.1 <-> 7.1.1.1
ldp: ldp conn is up; adj 0x617C5EBC, 8.1.1.1:11013 <-> 7.1.1.1:646
ldp: Send ldp hello; ATM3/0.1, src/dst 8.1.1.1/224.0.0.2, inst_id 1, tcatm
ldp: Rcvd ldp hello; ATM3/0.1, from 203.0.7.7 (203.0.7.7:2), intf_id 1, opt 0x8, tcatm
ldp: Send ldp hello; Ethernet1/1/1, src/dst 138.1.0.88/224.0.0.2, inst_id 0
ldp: Rcvd ldp hello; Ethernet1/1/1, from 10.105.0.9 (7.1.1.1:0), intf_id 0, opt 0xC
...
ldp: Send ldp hello; Ethernet1/1/1, src/dst 138.1.0.88/224.0.0.2, inst_id 0
ldp: Send ldp hello; ATM3/0.1, src/dst 8.1no tag ip
.0.2, inst_id 1, tcatm
ldp: disabling ldp on Ethernet1/1/1
ldp: Hold timer expired for adj 0x617C5EBC, will close conn
ldp: Closing ldp conn 8.1.1.1:11013 <-> 7.1.1.1:646, adj 0x617C5EBC
ldp: Adjacency 0x617C5EBC, 10.105.0.9 timed out
ldp: Adj 0x617C5EBC; state set to closed
ldp: Rcvd ldp hello; ATM3/0.1, from 203.0.7.7 (203.0.7.7:2), intf_id 1, opt 0x8, tcatm
ldp: Ignore Hello from 10.105.0.9, Ethernet1/1/1; no intf

Table 17 describes the significant fields in the sample display shown above.

Table 17 debug mpls ldp transport events Command Field Descriptions

Field
Description
ldp:

Identifies the source of the message as LDP.

adj 0xnnnnnnnn

Identifies the data structure used to represent the peer at the transport level. Useful for correlating debug output.

a.b.c.d (p.q.r.s:n)

Network address and LDP identifier of the peer.

intf_id 

Interface identifier (non-zero for LC-ATM interfaces; 0 otherwise).

opt 0xn 

Bits that describe options in the LDP discovery Hello packet:

0x1—Targeted Hello option

0x2—Send targeted Hello option

0x4—Transport address option

0x8—LDP Hello message (as opposed to TDP Hello message)


Related Commands

Command
Description

show mpls ldp discovery

Displays the status of the LDP discovery process.

debug mpls ldp transport connections

Displays information about the TCP connections used to support LDP sessions.


mpls ip (global configuration)

To enable MPLS forwarding of IPv4 packets along normally routed paths for the platform, use the mpls ip command in global configuration mode. To disable this feature, use the no form of the command.

mpls ip

no mpls ip

Syntax Description

This command has no optional keywords or arguments.

Defaults

Label switching of IPv4 packets along normally routed paths is enabled for the platform.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

MPLS forwarding of IPv4 packets along normally routed paths (sometimes called dynamic label switching) is enabled by this command. For a given interface to perform dynamic label switching, this switching function must be enabled for the interface as well as for the platform.

The no form of this command stops dynamic label switching for all platform interfaces regardless of the interface configuration; it also stops distribution of labels for dynamic label switching. However, the no form of this command does not affect the sending of labeled packets through label switch path (LSP) tunnels.

For an LC-ATM interface, the no form of this command prevents the establishment of label VCs originating at, terminating at, or passing through the platform.

Examples

In the following example, dynamic label switching is disabled for the platform, and all label distribution is terminated for the platform:

Router(config)# no mpls ip

Related Commands

Command
Description

mpls ip (interface configuration)

Enables label switching of IPv4 packets along normally routed paths for the associated interface.


mpls ip (interface configuration)

To enable MPLS forwarding of IPv4 packets along normally routed paths for a particular interface, use the mpls ip command in interface configuration mode. To disable this feature, use the no form of the command.

mpls ip

no mpls ip

Syntax Description

This command has no optional keywords or arguments.

Defaults

MPLS forwarding of IPv4 packets along normally routed paths for the interface is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

MPLS forwarding of IPv4 packets along normally routed paths is sometimes called dynamic label switching. If dynamic label switching has been enabled for the platform when this command is issued on an interface, label distribution for the interface begins with the periodic transmission of neighbor discovery Hello messages on the interface. When the outgoing label for a destination routed through the interface is known, packets for the destination are labeled with that outgoing label and forwarded through the interface.

The no form of this command causes packets routed out through the interface to be sent unlabeled; this form of the command also terminates label distribution for the interface. However, the no form of the command does not affect the sending of labeled packets through any LSP tunnels that might use the interface.

For an LC-ATM interface, the no form of this command prevents the establishment of label VCs beginning at, terminating at, or passing through the interface.

Examples

In the following example, label switching is enabled on the specified Ethernet interface:

Router(config)# configure terminal
Router(config-if)# interface e0/2
Router(config-if)# mpls ip

Related Commands

Command
Description

mpls ldp maxhops

Displays information about LDP neighbor discovery for an interface enabled for dynamic label switching.

show mpls interfaces

Displays information about one or more interfaces that have been configured for label switching.


mpls label protocol (global configuration)

To specify the default label distribution protocol for a platform, use the global mpls label protocol command in global configuration mode. To restore the image default, use the no form of the command.

mpls label protocol { ldp | tdp }

no mpls label protocol

Syntax Description

ldp

Specifies that LDP is the platform default label distribution protocol.

tdp

Specifies that TDP is the platform default label distribution protocol.


Defaults

If no protocol is explicitly configured by the global mpls label protocol command, TDP is the default label distribution protocol for the platform.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

If neither the global mpls label protocol ldp command nor the interface mpls label protocol ldp command is used, all label distribution sessions will use TDP.

To force all label distribution sessions to use LDP, use the global mpls label protocol ldp command and no interface mpls label protocol commands.

Examples

The following command establishes LDP as the label distribution protocol for the platform.

Router(config)# mpls label protocol ldp

Related Commands

Command
Description

show mpls interfaces

Displays MPLS information about interfaces, including the configured tag and/or label distribution protocol.


mpls label protocol (interface configuration)

To specify the label distribution protocol to be used on a given interface, use the mpls label protocol command in interface configuration mode. To disable this feature, use the no form of the command.

mpls label protocol { ldp | tdp | both }

no mpls label protocol

Syntax Description

ldp

Specifies that the label distribution protocol (LDP) is to be used on the interface.

tdp

Specifies that the tag distribution protocol (TDP) is to be used on the interface.

both

Specifies that both label distribution protocols are to be supported on the interface.


Defaults

If no protocol is explicitly configured for an interface, the default label distribution protocol for the platform is used. To set the platform default protocol, use the global mpls label protocol command.

Command Modes

Interface configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

To successfully establish a session for label distribution for a link connecting two LSRs, the link interfaces on the LSRs must be configured to use the same label distribution protocol. If there are multiple links connecting two LSRs, all of the link interfaces connecting the two LSRs must be configured to use the same protocol.

The both option is intended for use with interfaces to multiaccess networks, such as Ethernet and FDDI, where some peers might use LDP and others use TDP. When you specify the both option, the LSR sends both LDP and TDP discovery Hello messages and responds to both types of messages.

Examples

The following command establishes LDP as the label distribution protocol for the interface:

Router(config-if)# mpls label protocol ldp

Related Commands

Command
Description

show mpls interfaces

Displays MPLS information about interfaces, including the configured tag and/or label distribution protocol.


mpls ldp address-message

To specify advertisement of platform addresses to an LC-ATM LDP peer, use the mpls ldp address-message command in interface configuration mode. To disable this feature, use the no form of the command.

mpls ldp address-message

no mpls ldp address-message

Syntax Description

This command has no optional keywords or arguments.

Defaults

Do not send LDP Address and Address Withdraw messages to LC-ATM LDP peers.

Command Modes

Interface configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The LDP specification includes Address and Address Withdraw messages used by an LSR to advertise its addresses to its peers.

An LSR uses the addresses it learns from peers when operating in Downstream Unsolicited label advertisement mode to convert between route next hop addresses (found in the LSR routing table) and peer LDP identifiers.

The ability to map between the IP address and the peer LDP identifier is required so that

When the MPLS forwarding engine (LFIB) asks for labels for a given destination prefix/next hop address, the LSR can find the label learned (if any) from the next hop. The LSR maintains learned labels in its label information base (LIB) tagged by the LDP ID of the advertising LSR.

When the LSR learns a label for destination prefix P from an LDP peer, it can determine if that peer (known to the LSR by its LDP identifier) is currently the next hop for P.

In principle, an LSR operating in Downstream On Demand mode for an LC-ATM interface does not need this information for two reasons:

The LSR should know from the routing table the next hop interface.

Only one Downstream on Demand peer exists per LC-ATM interface.

Consequently, Cisco platforms do not normally send Address and Address Withdraw messages to LC-ATM peers.

Some LDP implementations might require the information learned in Address and Address Withdraw messages for LC-ATM. The mpls ldp address-message command is provided to enable interoperability with implementation vendors that require Address messages for LC-ATM.


Note Cisco platforms always advertise their addresses in Address and Address Withdraw messages for LDP sessions operating in Downstream Unsolicited label advertisement mode.


Examples

The following is an example use of the mpls ldp address-message command:

Router(config-if)# mpls ldp address-message

Related Commands

Command
Description

show mpls interfaces

Displays MPLS information about interfaces, including the configured label distribution protocol.


mpls ldp advertise-labels

To control the distribution of locally assigned (incoming) labels by means of LDP, use the mpls ldp advertise-labels command in global configuration mode. This command is used to control which labels are advertised to which LDP neighbors. To disable this feature, use the no form of the command.

mpls ldp advertise-labels [vrf vpn-name] [for prefix-access-list [to peer-access-list]]

no mpls ldp advertise-labels [vrf vpn-name] [for prefix-access-list [to peer-access-list]]

Syntax Description

vrf vpn-name

(Optional) Specifies the VPN routing/forwarding instance (vpn-name) for label advertisement.

for prefix-access-list

(Optional) Specifies which destinations should have their labels advertised.

to peer-access-list

(Optional) Specifies which LDP neighbors should receive label advertisements. An LSR is identified by its router ID, which consists of the first 4 bytes of its 6-byte LDP identifier.


Defaults

The labels of all destinations are advertised to all LDP neighbors.

If the vrf keyword is not specified, this command applies to the default routing domain.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP and to make the command consistent with the way Cisco IOS software interprets the prefix-access-list argument.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

To prevent the distribution of any locally assigned labels, use the no mpls ldp advertise-labels command with no optional parameters. To reenable the distribution of all locally assigned labels to all LDP neighbors, use the mpls ldp advertise-labels command with no optional parameters.

You can execute multiple mpls ldp advertise-labels commands. In the aggregate, such commands determine how the LSR advertises local labels. The following rules describe the effects of multiple commands:

1. Every mpls ldp advertise-labels ... command has a (prefix acl, peer acl) pair associated with it. The access list pair associated with the mpls ldp advertise-labels command (in the absence of both the for and to keywords) is (none, none); the access list pair associated with the mpls ldp advertise-labels for prefix acl command (in the absence of the to keyword) is (prefix-acl, none).

2. A given prefix can have, at most, one (prefix acl, peer acl) pair that "applies" to it, as described below:

a. A given (prefix acl, peer acl) pair "applies" to a prefix only if the prefix acl "matches" the prefix. A match occurs if the prefix acl permits the prefix.

b. If more than one (prefix acl, peer acl) pair from multiple mpls ldp advertise-labels commands matches a prefix, the (prefix acl, peer acl) pair in the first such command (as determined by the show running command) "applies" to the prefix.

3. When an LSR is ready to advertise a label for a prefix, the LSR:

a. Determines whether a (prefix acl, peer acl) pair applies to the prefix.

b. If none applies, and if the no mpls ldp advertise-labels command has been configured, the label for the prefix is not advertised to any peer; otherwise, the label is advertised to all peers.

c. If a (prefix acl, peer acl) pair applies to the prefix, and if the prefix acl "denies" the prefix, the label is not advertised to any peer.

d. If the prefix acl "permits" the prefix and the peer acl is none (that is, the command that "applies" to the prefix is an mpls ldp advertise-labels for prefix acl command without the to keyword), then the label is advertised to all peers.

e. If the prefix acl "permits" the prefix and there is a peer acl, then the label is advertised to all peers permitted by the peer acl.


Note The mpls ldp advertise-labels command has no effect on an LC-ATM interface. Such an interface behaves as though this command had not been executed.


Examples

In the following example, the router is configured to advertise no locally assigned labels to any LDP neighbors.

Router(config)# no mpls ldp advertise-labels

In the following example, the router is configured to advertise to all LDP neighbors only the labels for networks 10.101.0.0 and 10.221.0.0.

Router(config)# ip access-list standard pfx-filter
Router(config-std-nacl)# permit 10.101.0.0 0.0.255.255
Router(config-std-nacl)# permit 10.221.0.0 0.0.255.255
Router(config-std-nacl)# exit
Router(config)# mpls ldp advertise-labels for pfx-filter
Router(config)# no mpls ldp advertise-labels

In the following example, the router is configured to advertise the label for network 59.0.0.0 only to LSR 155.0.0.55, the label for network 35.0.0.0 only to LSR 133.0.0.33, and the labels for all other prefixes to all LSRs.

Router(config)# ip access-list standard pfx-filter1
Router(config-std-nacl)# permit 59.0.0.0
Router(config-std-nacl)# exit
Router(config)# ip access-list standard lsr-filter1
Router(config-std-nacl)# permit 155.0.0.55
Router(config-std-nacl)# exit
Router(config)# ip access-list standard pfx-filter2
Router(config-std-nacl)# permit 35.0.0.0
Router(config-std-nacl)# exit
Router(config)# ip access-list standard lsr-filter2
Router(config-std-nacl)# permit 133.0.0.33
Router(config-std-nacl)# exit
Router(config)# mpls ldp advertise-labels for pfx-filter1 to lsr-filter1
Router(config)# mpls ldp advertise-labels for pfx-filter2 to lsr-filter2

The output of the show mpls ip binding detail command includes the (prefix acl, peer acl) pairs that apply to each prefix. For this example, the applicable pairs are as shown below:

Router# show mpls ip binding detail
Advertisement spec:
	Prefix acl = pfx-filter1; Peer acl = lsr-filter1
	Prefix acl = pfx-filter2; Peer acl = lsr-filter2

  35.0.0.0/8, rev 109
	in label:     16
		Advertised to:
		133.0.0.33:0
	out label:    imp-null  lsr: 155.0.0.55:0     inuse
	out label:    imp-null  lsr: 133.0.0.33:0
	Advert acl(s): Prefix acl pfx-filter2, Peer acl lsr-filter2
  59.0.0.0/8, rev 108
	in label:     imp-null
		Advertised to:
		155.0.0.55:0
	out label:    16        lsr: 155.0.0.55:0
	out label:    19        lsr: 133.0.0.33:0
	Advert acl(s): Prefix acl pfx-filter1, Peer acl lsr-filter1
  113.0.0.33/32, rev 98
	out label:    imp-null  lsr: 133.0.0.33:0
  114.0.0.44/32, rev 99
	in label:     imp-null
		Advertised to:
		155.0.0.55:0           133.0.0.33:0
  133.0.0.33/32, rev 101
	in label:     20        
		Advertised to:
		155.0.0.55:0           133.0.0.33:0
	out label:    19        lsr: 155.0.0.55:0
	out label:    imp-null  lsr: 133.0.0.33:0     inuse
  144.0.0.44/32, rev 103
	in label:     imp-null
		Advertised to:
		155.0.0.55:0           133.0.0.33:0
	out label:    20        lsr: 155.0.0.55:0
	out label:    18        lsr: 133.0.0.33:0
  155.0.0.55/32, rev 104
	in label:     17
		Advertised to:
		155.0.0.55:0           133.0.0.33:0
	out label:    imp-null  lsr: 155.0.0.55:0     inuse
	out label:    17        lsr: 133.0.0.33:0
Router#

In the following example, the vrf keyword is specified to configure label advertisement in the VPN routing/forwarding instance named vpn1.

Router(config)# mpls ldp advertise-labels vrf vpn1 for pfx-filter1 to lsr-filter1
Router(config)# mpls ldp advertise-labels vrf vpn1 for pfx-filter2 to lsr-filter2

Related Commands

Command
Description

mpls ldp advertise-labels old-style

Use method of earlier software releases to interpret the for prefix-access-list parameter for the mpls ldp advertise-labels command.

show mpls ip binding detail (see the example command above)

Shows detailed information about label bindings, including the access lists, if any, controlling which local labels are advertised to which LDP neighbors.


mpls ldp advertise-labels old-style

To cause the interpretation of the for prefix-access-list parameter for mpls ldp advertise-labels commands to be interpreted according to the method used in earlier Cisco IOS software versions, use the mpls ldp advertise-labels old-style command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp advertise-labels [vrf vpn-name] old-style

no mpls ldp advertise-labels [vrf vpn-name] old-style

Syntax Description

vrf vpn-name

(Optional) Specifies the VPN routing/forwarding instance (vpn-name) for label advertisement.


This command has no keywords or arguments.

Defaults

If this command is not specified, the for prefix-access-list parameter in any mpls ldp advertise-labels commands is interpreted according to the rules specified under the "Usage Guidelines" heading for the mpls ldp advertise-labels command described in the preceding section.

If the vrf vpn-name parameter is not specified, this command applies to the default routing domain.

Command Modes

Global configuration

Command History

Release
Modification

12.0(14)ST

This command was introduced to reflect MPLS VPN support for LDP and to cause the for prefix-access-list parameter in the command to be interpreted in the same way as in earlier Cisco IOS releases.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The method for interpreting the for prefix-access-list parameter in mpls ldp advertise-labels commands is defined by Rule 2.a under the "Usage Guidelines" heading for the mpls ldp advertise-labels command described in the preceding section. This Rule 2.a follows normal access list conventions.

However, earlier Cisco IOS software versions used a different method for interpreting the for prefix-access-list parameter in mpls ldp advertise-labels commands. For those earlier software versions, Rule 2.a read as follows:

2. A given prefix can have, at most, one (prefix acl, peer acl) pair that "applies" to it.

a. A given (prefix acl, peer acl) pair "applies" to a prefix only if the prefix acl "matches" the prefix. A match occurs if the prefix acl explicitly permits or denies the prefix by means of a permit or deny command. A prefix acl that contains a permit any or deny any command matches any prefix.

This earlier Rule 2.a departed from normal access list conventions in that:

An explicit deny (including a deny any) that matches the prefix causes the (prefix acl, peer acl) pair to apply to the prefix.

Explicit deny any and implicit deny any (which all access lists have) have different effects, in that the explicit deny any causes the access list pair to apply to all prefixes, but the implicit deny any has no effect.

Use the mpls ldp advertise-labels old-style command to force the use of the old-style method of interpreting the for prefix-access-list parameter used by earlier software versions if the following apply:

A configuration developed for use with earlier software versions depends on this previous method for interpreting the for prefix-access-list parameter in mpls ldp advertise-labels commands.

It is inconvenient to update the configuration to work with Rule 2.a as it appears under the "Usage Guidelines" heading described in the previous section for the mpls ldp advertise-labels command.

Examples

The following command causes the old-style method of interpreting the for prefix-access-list parameter to be used in executing mpls ldp advertise-labels commands:

Router# mpls ldp advertise-labels old-style

In the following example, the vrf keyword is specified to configure label advertisement in the VPN routing/forwarding instance named vpn1.

Router(config)# mpls ldp advertise-labels vrf vpn1 old-style
Router(config)#

Related Commands

Command
Description

mpls ldp advertise-labels

Controls the distribution of locally assigned labels by means of LDP.


mpls ldp atm control-mode

To control the mode used for handling label binding requests on LC-ATM interfaces, use the mpls ldp atm control-mode command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp atm control-mode {ordered | independent}

no mpls ldp atm control-mode {ordered | independent}

Syntax Description

ordered

Delays a label binding in response to a Label Request message from an LDP neighbor until a label binding has been received from the next hop LDP neighbor for the destination in question.

independent

Returns a label binding immediately in response to a Label Request message from an LDP neighbor. Any packets for the destination in question are discarded by the LSR until a label binding from the next hop LSR has been received.


Defaults

The default is ordered control mode.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use of ordered control mode by an ATM device acting as a transit LSR in an ATM cloud ensures that the device will receive labeled packets to forward only after it has learned the outgoing labels required by MPLS to forward the packets. Ordered control mode relieves the device of the burden of reassembling cells into packets that must be forwarded by means of the normal (non-MPLS) packet forwarding or discard mechanisms.

Use of independent control mode on ATM transit LSRs might slightly reduce the time an ATM edge router must wait to use an ATM LSP it has initiated. Independent control mode eliminates the need for the edge router to wait for the Label Request/Label Mapping signaling to traverse the ATM cloud from edge router ingress to egress and back before it can send packets into the LSP. However, there is a risk that an ATM transit device might receive labeled packets before it has learned the outgoing labels required for MPLS forwarding, thus forcing the transit device to reassemble the cells into a packet that it is likely to discard.

Examples

In the following example, the mode for handling LDP Label Request messages is set to "independent" for the platform:

Router# mpls ldp atm control-mode independent

mpls ldp atm vc-merge

To control whether the vc-merge (multipoint-to-point) capability is supported for unicast label VCs, use the mpls ldp atm vc-merge command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp atm vc-merge

no mpls ldp atm vc-merge

Syntax Description

This command has no optional keywords or arguments.

Defaults

The ATM-VC merge capability is enabled by default if the hardware supports this feature; otherwise, the feature is disabled.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use of VC merge helps conserve ATM labels by allowing incoming LSPs from different sources for the same destination to be merged onto a single outgoing VC.

Examples

In the following example, the ATM-VC merge capability is disabled:

Router# no mpls ldp atm vc-merge

Related Commands

Command
Description

show mpls atm-ldp capability

Displays the ATM MPLS capabilities negotiated with LDP neighbors for LC-ATM interfaces.


mpls ldp backoff

To configure parameters for the LDP backoff mechanism, use the mpls ldp backoff command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp backoff initial-backoff maximum-backoff

no mpls ldp backoff initial-backoff maximum-backoff

Syntax Description

initial-backoff

A number between 5 and 2147483, inclusive, that defines the initial backoff value in seconds.

maximum-backoff

A number between 5 and 2147483, inclusive, that defines the maximum backoff value in seconds.


Defaults

The initial backoff value is 15 seconds and grows to a maximum value of 120 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The LDP backoff mechanism prevents two incompatibly configured LSRs from engaging in an unthrottled sequence of session setup failures. For example, an incompatibility arises when two neighboring routers attempt to perform LC-ATM (label-controlled ATM) but the two are using different ranges of VPI/VCI values for labels.

If a session setup attempt fails due to an incompatibility, each LSR delays its next attempt (that is, backs off), increasing the delay exponentially with each successive failure until the maximum backoff delay is reached.

The default settings correspond to the lowest settings for initial and maximum backoff values defined by the LDP protocol specification. You should change the settings from the default values only if such settings result in undesirable behavior.

Examples

The following command sets the initial backoff delay to 30 seconds and the maximum backoff delay to 240 seconds:

Router(config)# mpls ldp backoff 30 240

Related Commands

Command
Description

show mpls ldp backoff

Displays information about the configured session setup backoff parameters and any potential LDP peers with which session setup attempts are being throttled.

show mpls ldp parameters

Displays the session setup backoff parameters currently in effect for the LDP backoff mechanism.


mpls ldp discovery

To configure the interval between transmission of consecutive LDP discovery Hello messages, or the hold time for a discovered LDP neighbor, or the neighbors from which requests for targeted Hello messages may be honored, use the mpls ldp discovery command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp discovery { hello { holdtime | interval } seconds | targeted-hello
{
holdtime | interval } seconds | accept [ from acl ] }

no mpls ldp discovery { hello { holdtime | interval } | targeted-hello
{
holdtime | interval } | accept [from acl] }

Syntax Description

hello

Configures the intervals and hold times for directly connected neighbors.

targeted-hello

Configures the intervals and hold times for neighbors that are not directly connected (for example, LDP sessions that run between the endpoints of an LSP tunnel).

holdtime

Defines the period of time a discovered LDP neighbor is remembered without receipt of an LDP Hello message from the neighbor. The default is 15 seconds.

interval

Defines the period of time between the sending of consecutive Hello messages. The default is 5 seconds.

seconds

Defines the hold time or interval in seconds.

accept

Configures the router to respond to requests for targeted Hello messages from all neighbors or from neighbors specified by the optional acl argument.

from acl

(Optional) The IP access list that specifies the neighbor from which requests for targeted Hello messages may be honored.


Defaults

The default value for the holdtime argument is 15 (seconds) for link Hello messages and 45 (seconds) for targeted Hello messages.

The default value for the interval argument (seconds) is 5.

Requests for targeted Hello messages are not accepted from any neighbor.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When the discovery hold time elapses for a neighbor discovered on an interface or for a neighbor discovered by means of a targeted Hello message, the record associating the neighbor with that interface or that targeted Hello message source is discarded. If an LDP session exists with a neighbor, but a discovery record no longer exists for that neighbor, the LDP session is terminated.

Setting the hold time too high causes LDP to be slow in detecting link outages; setting the hold time too low might cause LDP to terminate sessions when a Hello message is dropped during traffic bursts on a link.

The exchange of targeted Hello messages between two nondirectly connected neighbors (N1 and N2) may occur in the following ways:

N1 may initiate the transmission of targeted Hello messages to N2, and N2 may send targeted Hello messages in response. In this situation, N1 is considered to be active and N2 is considered to be passive.

N1's targeted Hello messages carry a request that N2 send targeted Hello messages in response. To respond, N2's configuration must permit it to respond to N1. The mpls ldp discovery targeted-hello accept command is used to configure whether N1 may respond to requests for targeted Hello messages.

N1 and N2 may both be configured to initiate the transmission of targeted Hello messages to each other. In this situation, both are active.

Both, one, or neither of N1 and N2 may be passive, depending on whether they have been configured to respond to requests for targeted Hello messages from the other.


Note Normally, active transmission of targeted Hello messages by a router is triggered by some configuration action, such as an mpls ip command on a traffic engineering tunnel interface.


Examples

In the following example, the period of time for which a neighbor discovered on an interface is remembered if no Hello messages are received is set to 30 seconds:

Router# configure terminal
Router(config)# mpls ldp discovery hello holdtime 30

The following example configures the router to respond to requests for targeted Hello messages from neighbors 157.13.0.23 and 168.73.0.18:

Router(config)# ip access standard TRGT_ACCEPT
Router(config-nacl)# permit 157.13.0.23
Router(config-nacl)# permit 168.73.0.18
Router(config-nacl)# exit
Router(config)# mpls ldp discovery targeted-hello accept from TRGT_ACCEPT

Related Commands

Command
Description

mpls ldp holdtime

Changes the default time an LDP session is maintained in the absence of LDP messages from the session peer.

show mpls ldp discovery

Displays transmission and receipt of targeted Hello messages, indicating whether the local LSR is active, passive, or both.

show mpls ldp neighbor

Displays discovery sources for LDP sessions, indicating for targeted sessions whether the local LSR is active, passive, or both.

show mpls ldp parameters

Displays current LDP parameter settings.


mpls ldp discovery transport-address

To specify the transport address advertised in LDP Discovery Hello messages sent on an interface, use the mpls ldp discovery transport-address command in interface configuration mode. To disable this feature, use the no form of the command.

mpls ldp discovery transport-address { interface | IP address }

no mpls ldp discovery transport-address

Syntax Description

interface

Alternative to specify that the interface IP address should be advertised as the transport address.

IP address

Alternative to specify that the IP address should be advertised as the transport address.


Defaults

The default behavior when this command has not been issued for an interface depends on the interface type.

Unless the interface is a label-controlled atm (LC-ATM) interface, LDP advertises its LDP Router ID as the transport address in LDP Discovery Hello messages sent from the interface.

If the interface is an LC-ATM interface, no transport address is explicitly advertised in LDP Discovery Hello messages sent from the interface.

Command Modes

Interface configuration

Command History

Release
Modification

12.0(14)ST

This command was introduced.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The establishment of an LDP session between two routers requires a session TCP connection by which label advertisements can be exchanged between the routers. To establish the session TCP connection, each router must know the transport address (IP address) of the other router.

The LDP discovery mechanism provides the means for a router to advertise the transport address for its end of a session TCP connection. The transport address advertisement itself may be explicit, in which case it appears as part of the contents of Discovery Hello messages sent to the peer, or implicit, in which case it does not, and the peer uses the source IP address of received Hello messages for the peer's transport address.

The mpls ldp discovery transport-address command provides the means to modify the default behavior described above. When the interface alternative is specified, LDP advertises the IP address of the interface in LDP Discovery Hello messages sent from the interface. When the IP address alternative is specified, LDP advertises the specified IP address in LDP Discovery Hello messages sent from the interface.


Note When a router has multiple links connecting it to its peer device, the router must advertise the same transport address in the LDP Discovery Hello messages it sends on all such interfaces.


Examples

The following example specifies that the LDP transport address for interface pos2/0 should be the interface IP address; it also specifies that the IP address 145.22.0.56 of interface pos3/1 should be the LDP transport address.

Router(config#) interface pos2/0
Router(config-if)# mpls ldp discovery transport-address interface
Router(config#) interface pos3/1
Router(config-if)# mpls ldp discovery transport-address 145.22.0.56

Related Commands

Command
Description

show mpls ldp discovery

Displays the status of the LDP discovery process, including the transport addresses of discovered peers if they differ from the peers' LDP router IDs.

show mpls ldp neighbor

Displays the status of LDP sessions, including the transport addresses for each of the session TCP connections.


mpls ldp explicit-null

To cause a router to advertise an Explicit Null label in situations where it would normally advertise an Implicit Null label, use the mpls ldp explicit-null command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp explicit-null [ for prefix-acl | to peer-acl | for prefix-acl to peer-acl ]

no mpls ldp explicit-null

Syntax Description

for prefix-acl

(Optional) Specifies prefixes for which Explicit Null should be advertised in place of Implicit Null.

to peer-acl

(Optional) Specifies LDP peers to which Explicit Null should be advertised in place of Implicit Null.


Defaults

The default behavior is to advertise Implicit Null for directly connected routes unless the command mpls ldp explicit-null has been executed.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Normally, LDP advertises an Implicit Null label for directly connected routes. The Implicit Null label causes the previous hop (penultimate) router to do penultimate hop popping. Situations exist where it might be desirable to prevent the penultimate router from performing penultimate hop popping and to force it to replace the incoming label with the Explicit Null label.

When you issue the mpls ldp explicit-null command, Explicit Null is advertised in place of Implicit Null for directly connected prefixes permitted by prefix-acl to peers permitted by peer-acl.

If you do not specify the prefix-acl argument in the command, Explicit Null is advertised in place of Implicit Null for all directly connected prefixes.

If you do not specify the peer-acl argument in the command, Explicit Null is advertised in place of Implicit Null to all peers.

Examples

The following command causes Explicit Null to be advertised for all directly connected routes to all LDP peers:

Router(config)# mpls ldp explicit-null

The following command sequence causes Explicit Null to be advertised for directly connected route 137.5.0.0 to all LDP peers and Implicit Null to be advertised for all other directly connected routes:

Tagsw-r8(config)# mpls ldp explicit-null
Tagsw-r8(config)# ip access-list standard adv-exp-null
Tagsw-r8(config-std-nacl)# permit 137.5.0.0
Tagsw-r8(config-std-nacl)# deny any
Tagsw-r8(config-std-nacl)#

Related Commands

Command
Description

show mpls ip binding

Displays known label bindings.


mpls ldp holdtime

To change the time for which an LDP session is maintained in the absence of LDP messages from the session peer, use the mpls ldp holdtime command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp holdtime seconds

no mpls ldp holdtime seconds

Syntax Description

seconds

A number between 15 and 2147483, inclusive, that defines the time, in seconds, an LDP session is maintained in the absence of LDP messages from the session peer.


Defaults

The default value for the seconds argument is 180.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When an LDP session is established between two LSRs, the hold time used for the session is the lower of the values configured on the two LSRs.

Examples

In the following example, the hold time of LDP sessions is configured for 30 seconds:

Router# mpls ldp holdtime 30

Related Commands

Command
Description

show mpls ldp parameters

Displays current LDP parameter settings.

show mpls atm-ldp bindings

Configures parameters for the LDP discovery mechanism.


mpls ldp loop-detection

To enable the LDP optional loop detection mechanism, use the mpls ldp loop-detection global configuration command. To disable this feature, use the no form of the command.

mpls ldp loop-detection

no mpls ldp loop-detection

Syntax Description

This command has no optional keywords or arguments.

Defaults

LDP loop detection is off.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The LDP loop detection mechanism is intended for use in networks of non-TTL (time-to-live) decrementing devices (for example, ATM switches) that are incapable of fairly allocating device resources among traffic flows.

When configured, the LDP loop detection mechanism is used with the Downstream on Demand method of label distribution, supplementing the Downstream on Demand hop count mechanism to detect looping LSPs that might occur during routing transients. When looping LSPs are detected, the loop is not set up.

Examples

The following command sets the LDP loop detection mechanism on:

Router(config)# mpls ldp loop-detection

Related Commands

Command
Description

mpls ldp maxhops

Limits the number of hops permitted for LSPs to a specified value. An LSP with more hops than the specified value is treated as one with a loop that will not be established.


mpls ldp maxhops

To limit the number of hops permitted in an LSP established by the Downstream on Demand method of label distribution, use the mpls ldp maxhops command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp maxhops number

no mpls ldp maxhops

Syntax Description

number

A number between 1 and 255, inclusive, that defines the maximum hop count.


Defaults

The default value for the maximum hop count argument (number) is 254.

Command Modes

Global configuration

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When an ATM LSR initiates a request for a label binding, it sets the hop count value in the Label Request message to 1. Subsequent ATM-LSRs along the path to the edge of the ATM label switching region increment the hop count before forwarding the Label Request message to the next hop.

When an ATM LSR receives a Label Request message, it does not send a Label Mapping message in response, nor does it propagate the request to the destination next hop if the hop count value in the request equals or exceeds the maxhops value. Instead, the ATM LSR returns an error message that specifies that the maximum allowable hop count has been reached. This threshold is used to prevent forwarding loops in the setting up of label switch paths across an ATM region.

Examples

In the following example, the hop count limit is set to 10:

Router(config)# mpls ldp maxhops 10

Related Commands

Command
Description

mpls ldp neighbor

Enables the optional LDP loop detection mechanism.

show mpls atm-ldp bindings

Displays the requested entries from the ATM LDP label binding database, including the hop counts for LSPs that originate on the platform.

show mpls ip binding

Displays the requested entries from the ATM LDP label binding database, including the hop counts for LSPs that originate on the platform.


mpls ldp neighbor

To configure session Transmission Control Protocol (TCP) connections and routing options for a specified neighbor, use the mpls ldp neighbor command in global configuration mode. To disable these options for the specified neighbor, use the no form of the command.

mpls ldp neighbor [vrf vpn-name] ip addr {password [0-7] pswd-string | implicit-withdraw}

no mpls ldp neighbor [vrf vpn-name] ip addr [password [0-7] pswd-string] [implicit-withdraw]

Syntax Description

vrf vpn-name

(Optional) The VPN routing/forwarding instance for the specified neighbor.

ip addr

The router ID (IP address) that identifies a neighbor.

password [0-7]

An encryption method for storing the supplied password in the configuration. Optional with the no command.

Note The [0-7] encryption option is not supported for this release.

pswd-string

The password key to be used for computing MD5 checksums for the session TCP connection with the specified neighbor.

implicit-withdraw

Allows the router to advertise a new label for a Forwarding Equivalence Class (FEC) without sending a Label-Withdraw message to withdraw the previously advertised label. Optional with the no command.


Defaults

Unless the TCP MD5 Signature Option is explicitly configured with the password pswd-string keyword and argument for session TCP connections, the option is not used.

When the vrf keyword is not specified in this command, the LDP neighbor is configured in the default routing domain.

When the implicit-withdraw keyword is not specified, LDP withdraws the previously advertised label before advertising a new label for a FEC.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.0(21)ST

This command was modified to add the implicit-withdraw keyword.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

You must include either the password keyword or the implicit-withdraw keyword with the mpls ldp neighbor command. You can configure both options on the router, but not in the same command.

Router(config)# mpls ldp neighbor 10.10.10.10 password cisco

Router(config)# mpls ldp neighbor 10.10.10.10 implicit-withdraw

Invoking the no form of the command without a specific option disables all options that you configured with the mpls ldp neighbor command for a particular neighbor. For example, both options set in the previous mpls ldp neighbor commands for the neighbor with the router ID 10.10.10.10 are disabled with this command:

Router(config)# no mpls ldp neighbor 10.10.10.10 

To disable a specific option, use the no form of the command with the specific option. This command removes the implicit-withdraw option without disabling the authentication option configured for the neighbor with the router ID 10.10.10.10:

Router(config)# no mpls ldp neighbor 10.10.10.10 implicit-withdraw

You can invoke authentication between two LDP peers, verifying each segment sent on the TCP connection between the peers. To do so, you must configure authentication on both LDP peers using the same password; otherwise, the peer session is not established.

The authentication capability uses the MD5 (Message Digest 5) algorithm. MD5, an algorithm used in conjunction with SNMP, verifies the integrity of the communication, authenticates the origin of the message, and checks for timeliness.

Invoking the mpls ldp neighbor command causes the generation and checking of the MD5 digest for every segment sent on the TCP connection.

Configuring a password for an LDP neighbor causes an existing LDP session to be torn down and a new session to be established.

If a router has a password configured for a neighbor, but the neighbor router does not have a password configured, a message such as the following appears on the console while the two routers attempt to establish an LDP session:

%TCP-6-BADAUTH: No MD5 digest from [peer's IP address]:11003 to [local router's 
IP address]:179

Similarly, if the two routers have different passwords configured, a message such as the following appears on the console:

%TCP-6-BADAUTH: Invalid MD5 digest from [peer's IP address]:11004 to [local router's 
IP address]:179

By default, in Cisco IOS Release 12.0(21)ST and later, LDP withdraws the previously advertised label using a withdraw message before advertising a new label for a FEC. In Cisco IOS releases prior to 12.0(21)ST, LDP did not withdraw a previously advertised label before advertising a new label for a FEC. In these older releases, the new label advertisement served as an implied withdraw and LDP did not send a withdraw message. To cause LDP to operate as it did in releases before Cisco IOS 12.0(21)ST, that is, LDP will advertise a new label for a FEC without first withdrawing the previously advertised label, use the implicit-withdraw keyword with this command.

Router(config)# mpls ldp neighbor 10.10.10.10 implicit-withdraw

Using the implicit-withdraw keyword avoids the overhead of label withdraw and label release message exchanges.

To disable the implicit-withdraw option, use the no form of the command with the implicit-withdraw keyword. This returns the router to the default, which requires that LDP withdraw the previously advertised label for a FEC before advertising a new label.

Router(config)# no mpls ldp neighbor 10.10.10.10 implicit-withdraw

Examples

In the following example, the string onethirty9 is configured as the password key for use with MD5 for the neighbor whose router ID is 139.27.0.15:

Router(config)# mpls ldp neighbor 139.27.0.15 password onethirty9

In the following example, the string cisco is configured as the password for use with MD5 for the LDP neighbor having router ID 4.4.4.4 in the VPN routing/forwarding instance named vpn1:

Router(config)# mpls ldp neighbor vrf vpn1 4.4.4.4 password cisco

In the following example, LDP will not send a Label-Withdraw message to the neighbor whose router ID is 10.10.10.10 when a need exists to change the previously advertised label for a FEC:

Router(config)# mpls ldp neighbor 10.10.10.10 implicit-withdraw

mpls ldp router-id

To specify a preferred interface for determining the LDP router ID, use the mpls ldp router-id command in global configuration mode. To disable this feature, use the no form of the command.

mpls ldp router-id interface [ force ]

no mpls ldp router-id

Syntax Description

interface

Causes the IP address of the specified interface to be used as the LDP router ID, provided that the interface is operational.

force

(Optional) Alters the behavior of the mpls ldp router-id command, as described in the "Usage Guidelines" section below.


Defaults

If the mpls ldp router-id command is not executed, the LDP router ID is determined as follows:

a. The IP addresses of all operational interfaces are examined.

b. If these IP addresses include loopback interface addresses, the largest such loopback address is selected as the LDP router ID.

c. Otherwise, the largest IP address pertaining to an operational interface is selected as the LDP router ID.

Command Modes

Global configuration

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.0(14)ST

This command was modified to alter the behavior of the command (see "Usage Guidelines" below).

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The normal (default) method for determining the LDP router ID may result in a router ID that is not usable in certain situations. For example, an IP address selected as the LDP router ID might not be advertisable by the routing protocol to a neighboring router. The mpls ldp router-id command provides a means for specifying an interface whose IP address is to be used as the LDP router ID. Note, however, that the specified interface must be operational in order for its IP address to be used as the LDP router ID.

When executed without the force option, the mpls ldp router-id command modifies the method for determining the LDP router ID by causing selection of the IP address of the specified interface (provided that the interface is operational) the next time it is necessary to select an LDP router ID. The effect of the command is delayed until the next time it is necessary to select an LDP router ID, which is typically the next time the interface whose address is the current LDP router ID is shut down or the address itself is deconfigured.

When executed with the force option, the effect of the mpls ldp router-id command depends on the current state of the specified interface:

a. If the interface is up (operational) when the mpls ldp router-id force command is issued and if its IP address is not currently the LDP router ID, the LDP router ID is forcibly changed to the IP address of the interface. This forced change in the LDP router ID tears down any existing LDP sessions, releases label bindings learned via the LDP sessions, and interrupts MPLS forwarding activity associated with the bindings.

b. If the interface is down when the mpls ldp router-id force command is issued, when the interface transitions to up, the LDP router ID is forcibly changed to the IP address of the interface. This forced change in the LDP router ID tears down any existing LDP sessions, releases label bindings learned via the LDP sessions, and interrupts MPLS forwarding activity associated with the bindings.

Examples

The following example shows that the pos2/0/0 interface has been specified as the preferred interface for use in determining the LDP router ID. The IP address of such a specified interface is used as the LDP router ID.

Router(config)# mpls ldp router-id pos2/0/0

Related Commands

Command
Description

show mpls ldp discovery

Displays the status of the LDP discovery process, including the local LDP router ID and the LDP router IDs of discovered LSRs.


show mpls atm-ldp bindings

To display specified entries from the ATM label binding database, use the show mpls atm-ldp bindings command in privileged EXEC mode. The ATM label binding database contains entries for label VCs on LC-ATM interfaces.

show mpls atm-ldp bindings [network {mask | length}] [local-label vpi vci] [remote-label vpi vci] [neighbor interface]

Syntax Description

network

(Optional) Defines the destination network number.

mask

Defines the network mask in the form A.B.C.D (destination prefix).

length

Defines the mask length (1 to 32).

local-label vpi vci

(Optional) Selects the label values assigned by this router. (VPI range is 0 to 4095. VCI range is 0 to 65535.)

remote-label vpi vci

(Optional) Selects the label values assigned by the other router. (VPI range is 0 to 4095. VCI range is 0 to 65535.)

neighbor interface

(Optional) Selects the label values assigned by the neighbor on a specified interface.


Defaults

The entire ATM label binding database is displayed if no optional parameters or keywords are specified.


Note To display information about entries in the label binding database for interfaces other than ATM interfaces, use the show mpls ip binding command.


Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(4)T

The VPI range of values for this command was extended to 4095.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Command output can show a summary of entries from the entire database, or the output can be limited to a subset of entries based on the following:

Specific prefix

Specific VC label value

Specific assigning interface


Note This command displays ATM label bindings learned by LDP or TDP.



Note The command show mpls ip binding includes the output generated by show mpls atm-ldp bindings as well as information about label bindings for packet interfaces.


Examples

The following shows sample output from the show mpls atm-ldp bindings command:

Router# show mpls atm-ldp bindings

 Destination: 10.24.0.0/24
    Tailend Router ATM1/0.1 1/39 Active, VCD=3
 Destination: 10.15.0.15/32
    Tailend Router ATM1/0.1 1/33 Active, VCD=4
 Destination: 203.0.7.7/32
    Headend Router ATM1/0.1 (2 hops) 1/34  Active, VCD=810

The following is sample output from the show mpls atm-ldp bindings command on an ATM switch:

Router# show mpls atm-ldp bindings

Destination: 150.0.0.0/16
    Tailend Switch ATM0/0/3 1/35 Active -> Terminating Active
Destination: 4.4.4.4/32
    Transit ATM0/0/3 1/33 Active -> ATM0/1/1 1/33 Active

Table 18 describes the significant fields in the sample display shown above.

Table 18 show mpls atm-ldp bindings Command Field Descriptions 

Field
Description
Destination

Destination (network/mask).

Headend Router
Tailend Router
Tailend Switch
Transit

Indicates types of VCs. Options include the following:

Tailend—VC that terminates at this platform

Headend—VC that originates at this router

Transit—VC that passes through a switch

 ATM1/0.1

Interface.

1/35 

VPI/VCI.

Active

Indicates VC state. Options include the following:

Active—Set up and working

Bindwait—Waiting for a response

Remote Resource Wait—Waiting for resources (VPI/VCI space) to be available on the downstream device

Parent Wait—Transit VC input side waiting for output side to become active

VCD=2

Virtual circuit descriptor number.


show mpls atm-ldp bindwait

To display the number of bindings waiting for label assignments from a remote MPLS ATM switch, use the show mpls atm-ldp bindwait command in privileged EXEC mode.

show mpls atm-ldp bindwait

Syntax Description

This command has no optional keywords or options.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.0(5)T

This command was introduced.

12.2(4)T

This command was updated to reflect the MPLS IETF terminology.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to display information about virtual circuits (VCs) in the bindwait state.

Examples

The following shows sample output from the show mpls atm-ldp bindwait command.

Router# show mpls atm-ldp bindwait

Waiting for bind on ATM1/0.2
  3.3.3.1/32          3.3.3.1/32          3.3.3.2/32          
  3.3.3.2/32          3.3.3.3/32          3.3.3.3/32          
  3.3.3.4/32          3.3.3.4/32          3.3.3.5/32          
  3.3.3.5/32          3.3.3.6/32          3.3.3.6/32          
  3.3.3.7/32          3.3.3.7/32          3.3.3.8/32          
  3.3.3.8/32          3.3.3.9/32          3.3.3.9/32 ...

end

If everything is working properly, this command does not display any output.

Related Commands

Command
Description

show mpls atm-ldp bindings

Displays requested entries from the ATM LDP label binding database.



show mpls atm-ldp capability

To display the ATM MPLS capabilities negotiated with LDP neighbors for LC-ATM interfaces, use the show mpls atm-ldp capability command in privileged EXEC mode.

show mpls atm-ldp capability

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command always displays all of the ATM MPLS capabilities negotiated with all of the LDP neighbors.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

When two LSRs establish an LDP session, they negotiate parameters for the session, such as the range of VPIs and VCIs that will be used as labels.

This command displays the ATM MPLS capabilities negotiated by LDP or TDP.

Examples

The following shows sample output from the show mpls atm-ldp capability command.

Router# show mpls atm-ldp capability

               VPI           VCI           Alloc   Odd/Even  VC Merge 
ATM0/1/0       Range         Range         Scheme  Scheme    IN   OUT  
  Negotiated   [100 - 101]   [33 - 1023]   UNIDIR            -    -    
  Local        [100 - 101]   [33 - 16383]  UNIDIR            EN   EN   
  Peer         [100 - 101]   [33 - 1023]   UNIDIR            -    -    
 
               VPI           VCI           Alloc   Odd/Even  VC Merge     
ATM0/1/1       Range         Range         Scheme  Scheme    IN   OUT  
  Negotiated   [201 - 202]   [33 - 1023]   BIDIR             -    -    
  Local        [201 - 202]   [33 - 16383]  UNIDIR  ODD       NO   NO   
  Peer         [201 - 202]   [33 - 1023]   BIDIR   EVEN      -    -    

Table 19 describes the significant fields shown in the sample display above.

Table 19 show mpls atm-ldp capability Command Field Descriptions 

Field
Description
VPI Range

Minimum and maximum numbers of VPIs supported on this interface.

VCI Range

Minimum and maximum numbers of VCIs supported on this interface.

Alloc Scheme

Indicates the applicable allocation scheme, as follows:

UNIDIR—Unidirectional capability indicates that the peer can, within a single VPI, support binding of the same VCI to different prefixes on different directions of the link.

BIDIR—Bidirectional capability indicates that within a single VPI, a single VCI can appear in one binding only. In this case, one peer allocates bindings in the even VCI space, and the other in the odd VCI space. The system with the lower LDP identifier assigns even-numbered VCIs.

The negotiated allocation scheme is UNIDIR, if and only if, both peers have UNIDIR capability. Otherwise the allocation scheme is BIDIR.

Note These definitions for unidirectional and bidirectional are consistent with normal ATM usage of the terms; however, they are exactly opposite from the definitions for them in the IETF LDP specification.

Odd/Even Scheme

Indicates whether the local device or the peer is assigning an odd- or even-numbered VCI when the negotiated scheme is BIDIR. It does not display any information when the negotiated scheme is UNIDIR.

VC Merge

Indicates the type of VC merge support available on this interface. There are two possibilities, as follows:

IN—Indicates the input interface merge capability. IN accepts the following values:

EN—The hardware interface supports VC merge, and VC merge is enabled on the device

DIS—The hardware interface supports VC merge and VC merge is disabled on the device

NO—The hardware interface does not support VC merge

OUT—Indicates the output interface merge capability. OUT accepts the same values as the input merge side.

The VC merge capability is meaningful only on ATM switches. This capability is not negotiated.

Negotiated

Indicates the set of options that both LDP peers have agreed to share on this interface. For example, the VPI or VCI allocation on either peer remains within the negotiated range.

Local

Indicates the options supported locally on this interface.

Peer

Indicates the options supported by the remote LDP peer on this interface.


Related Commands

Command
Description

mpls ldp atm vc-merge

Controls whether vc-merge (multipoint-to-point) is supported for unicast label VCs.


show mpls atm-ldp summary

To display summary information about all the entries in the ATM label binding database, use the show mpls atm-ldp summary command in privileged EXEC mode.

show mpls atm-ldp summary

Syntax Description

This command has no optional keywords or options.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1 CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

Use this command to display dynamic ATM accounting information.

Examples

The following shows sample output from the show mpls atm-ldp summary command:

Router# show mpls atm-ldp summary

Total number of destinations: 406
 
ATM label bindings summary
interface      total   active  local   remote  Bwait   Rwait   IFwait  
ATM0/0/0       406     406     404     2       0       0       0       
ATM0/0/1       406     406     3       403     0       0       0       

Table 20 describes the significant fields in the sample display shown above.

Table 20 show mpls atm-ldp summary Command Field Descriptions 

Field
Description
Total number of 
destinations:

The number of known destination address prefixes.

interface 

The name of an interface with associated ATM label bindings.

total

The total number of ATM labels on this interface.

active

The number of ATM labels in an "active" state that are ready to use for data transfer.

local

The number of ATM labels assigned by this LSR on this interface.

remote

The number of ATM labels assigned by the neighbor LSR on this interface.

Bwait

The number of bindings that are waiting for a label assignment from the neighbor LSR.

Rwait

The number of bindings that are waiting for resources (VPI/VCI space) to be available on the downstream device.

IFwait

The number of bindings that are waiting for learned labels to be installed for switching use.


Related Commands

Command
Description

show isis database verbose

Displays the requested entries from the ATM LDP label binding database.


show mpls interfaces

To display information about one or more or all interfaces that have been configured for label switching, use the show mpls interfaces command in privileged EXEC mode.

show mpls interfaces [vrf vpn-name] [interface] [detail]

show mpls interfaces [all]

Syntax Description

vrf vpn-name

(Optional) Displays information about the interfaces that have been configured for label switching for the specified VPN routing/forwarding instance (vpn-name).

interface

(Optional) Defines the interface about which to display label switching information.

detail

(Optional) Displays detailed label switching information for the specified interface.

all

(Optional) When the all keyword is specified alone in this command, information about the interfaces configured for label switching is displayed for all VPNs, including the VPNs in the default routing domain.


Defaults

If no optional keyword or parameter is specified in this command, summary information is displayed for each interface that has been configured for label switching in the default routing domain.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

This command shows MPLS information about the specified interface, or about all of the interfaces for which MPLS has been configured.

Examples

The following shows sample output generated by the show mpls interfaces command:

Router# show mpls interfaces
Interface              IP         Tunnel   Operational
Ethernet1/1/1          Yes (tdp)  No       No          
Ethernet1/1/2          Yes (tdp)  Yes      No          
Ethernet1/1/3          Yes (tdp)  Yes      Yes         
POS2/0/0               Yes (tdp)  No       No          
ATM0/0.1               Yes (tdp)  No       No          (ATM labels)
ATM3/0.1               Yes (ldp)  No       Yes         (ATM labels)
ATM0/0.2               Yes (tdp)  No       Yes         


Note If an interface uses LC-ATM procedures, the associated line in the display is flagged with the notation (ATM labels).


Table 21 describes the significant fields in the sample display shown above.

Table 21 show mpls interfaces Command Field Descriptions 

Field
Description
Interface

Interface name.

IP 

"Yes" if IP label switching (sometimes called hop-by-hop label switching) has been enabled on this interface.

Tunnel

"Yes" if LSP tunnel labeling has been enabled on this interface.

Operational

Operational state. "Yes" if packets are being labeled.


The following is sample output from the show mpls interfaces command when you specify the detail keyword:

Router# show mpls interfaces detail
Interface Ethernet1/1/1:
        IP labeling enabled (tdp)
        LSP Tunnel labeling not enabled
        MPLS operational
        MPLS turbo vector
        MTU = 1500
Interface POS2/0/0:
        IP labeling enabled (ldp)
        LSP Tunnel labeling not enabled
        MPLS not operational
        MPLS turbo vector
        MTU = 4470
Interface ATM3/0.1:
        IP labeling enabled (ldp)
        LSP Tunnel labeling not enabled
        MPLS operational
        MPLS turbo vector
        MTU = 4470
        ATM labels: Label VPI = 1
                Label VCI range = 33 - 65535
                Control VC = 0/32

The following is sample output from the show mpls interfaces command when you specify the all keyword:

Router# show mpls interfaces all
Interface              IP            Tunnel   Operational 
ATM1/1/0.1             Yes (tdp)     No       Yes 

VRF vpn1:
ATM3/0/0.1             Yes (ldp)     No       Yes 

VRF vpn2:
ATM3/0/0.2             Yes (ldp)     No       Yes 

VRF vpn3:
ATM3/0/0.3             Yes (ldp)     No       Yes 

VRF vpn4:
ATM3/0/0.4             Yes (ldp)     No       Yes 

VRF vpn5:
ATM3/0/0.5             Yes (ldp)     No       Yes 

VRF vpn6:
Interface              IP            Tunnel   Operational 
ATM3/0/0.6             Yes (ldp)     No       Yes 

VRF vpn7:
ATM3/0/0.7             Yes (ldp)     No       Yes 

VRF vpn8:
ATM3/0/0.8             Yes (ldp)     No       Yes 

VRF vpn9:
ATM3/0/0.9             Yes (ldp)     No       Yes 

VRF vpn10:
ATM3/0/0.10            Yes (ldp)     No       Yes 

VRF vpn11:
ATM3/0/0.11            Yes (ldp)     No       Yes 

VRF vpn12:
ATM3/0/0.12            Yes (ldp)     No       Yes 
.
.
.

Related Commands

Command
Description

mpls ip (global configuration)

Enables label switching of IPv4 packets on all interfaces.

mpls ip (interface configuration)

Enables label switching of IPv4 packets on the associated interface.

mpls label protocol (global configuration)

Specifies the label distribution protocol to be used on a given platform.

mpls label protocol (interface configuration)

Specifies the label distribution protocol to be used on a given interface.

mpls traffic-eng tunnels (global configuration)

Enables MPLS traffic engineering tunneling signaling on a device.

mpls traffic-eng tunnels (interface configuration)

Enables MPLS traffic engineering tunneling signaling on an interface.


show mpls ip binding

To display specified information about label bindings learned by LDP, use the show mpls ip binding command in privileged EXEC mode. To summarize information about label bindings learned by LDP, use the show mpls ip binding summary command in privileged EXEC mode.

show mpls ip binding [vrf vpn-name] [network {mask | length} [longer-prefixes]]
[
local-label {atm vpi vci | label  [- label]}]
[
remote-label {atm vpi vci | label  [- label]}]
[
neighbor address] [local]
[
interface interface] [generic | atm]

show mpls ip binding summary

Syntax Description

vrf vpn-name

(Optional) Displays the label bindings for the specified VPN routing/forwarding instance (vpn-name).

network

(Optional) Defines the destination network number.

mask

Defines the network mask, written as A.B.C.D.

length

Defines the mask length (1 to 32 characters).

longer-prefixes

(Optional) Selects any prefix that matches the mask with length to 32.

local-label atm vpi vci

(Optional) Displays entry with locally assigned atm label that matches the specified atm label value. (VPI range is 0 to 4095. VCI range is 0 to 65535.)

local-label label - label

(Optional) Displays entries with locally assigned label(s) that match the specified label value(s). Use the label - label argument to indicate the label range.

remote-label atm vpi vci

(Optional) Displays entries with remotely assigned atm label values learned from neighbor routers that match the specified atm label value. (VPI range is 0 to 4095. VCI range is 0 to 65535.)

remote-label label - label

(Optional) Displays entries with remotely assigned label(s) learned from neighbor routers that match the specified label value(s). Use the label - label argument to indicate the label range.

neighbor address

(Optional) Displays label bindings assigned by the selected neighbor.

local

(Optional) Displays the local label bindings.

interface interface

(Optional) Displays label bindings associated with the specified interface (for LC-ATM only).

generic

(Optional) Displays only generic (non-LC-ATM) label bindings.

atm

(Optional) Displays only LC-ATM label bindings.


Defaults

All label bindings are displayed when no optional parameters are specified.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(4)T

The VPI range of values was extended to 4095.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The show mpls ip binding command displays label bindings learned by LDP or TDP.

A request can specify that the entire database be displayed, that a summary of entries from the database be displayed, or that the display be limited to a subset of entries. The subset can be limited according to any of the following:

Prefix

Input or output label values or ranges

Neighbor advertising the label

Interface for label bindings of interest (LC-ATM only)

Generic (non-LC-ATM) label bindings

LC-ATM label bindings

Examples

The following shows sample output from the show mpls ip binding command. The output shows all of the label bindings in the database.

Router# show mpls ip binding 
  34.0.0.0/8 
        in label:     20        
        out label:    26        lsr: 155.0.0.55:0    
        out vc label: 1/80      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    ingress 3 hops (vcd 49) 
  45.0.0.0/8 
        in label:     25        
        in vc label:  1/36      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 55) 
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
  66.66.0.66/32 
        in label:     26        
        in vc label:  1/39      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 58) 
        out label:    16        lsr: 155.0.0.55:0     inuse
  133.0.0.33/32 
        in label:     23        
        out label:    22        lsr: 155.0.0.55:0    
        out vc label: 1/83      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    ingress 3 hops (vcd 52) 
  144.0.0.44/32 
        in label:     61        
        out label:    27        lsr: 155.0.0.55:0     inuse
  150.88.0.0/16 
        in label:     28        
        in vc label:  1/40      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 59) 
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
  166.47.0.0/16 
        in label:     33        
        in vc label:  1/46      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 65) 
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
  194.44.44.0/24 
        in label:     24        
        in vc label:  1/37      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 56) 
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
Router# 

In the following example, a request is made for the display of the label binding information for prefix 194.44.44.0/24:

Router# show mpls ip binding 194.44.44.0 24
  194.44.44.0/24 
        in label:     24        
        in vc label:  1/37      lsr: 203.0.7.7:2      ATM1/0.8
                      Active    egress (vcd 56) 
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
Router# 

In the following example, the local-label argument is used to request that label binding information be displayed for the prefix(es) with local label 58:

Router# show mpls ip binding local-label 58
  166.253.0.0/16 
        in label:     58        
        out label:    imp-null  lsr: 155.0.0.55:0     inuse
Router#

In the following example, the label bindings for the VPN routing/forwarding instance named vpn1 are displayed.

Router# show mpls ip binding vrf vpn1
3.3.0.0/16 
        in label:    117       
        out label:   imp-null  lsr:14.14.14.14:0   
  13.13.13.13/32 
        in label:    1372      
        out label:   268       lsr:14.14.14.14:0   
  14.14.14.14/32 
        in label:    118       
        out label:   imp-null  lsr:14.14.14.14:0   
  15.15.15.15/32 
        in label:    1370      
        out label:   266       lsr:14.14.14.14:0   
  16.16.16.16/32 
        in label:    8370      
        out label:   319       lsr:14.14.14.14:0   
  18.18.18.18/32 
        in label:    21817     
        out label:   571       lsr:14.14.14.14:0   
  30.2.0.0/16 
        in label:    6943      
        out label:   267       lsr:14.14.14.14:0   
  30.3.0.0/16 
        in label:    2383      
        out label:   imp-null  lsr:14.14.14.14:0   
  30.4.0.0/16 
        in label:    77        
        out label:   imp-null  lsr:14.14.14.14:0   
  30.5.0.0/16 
        in label:    20715     
        out label:   504       lsr:14.14.14.14:0   
  30.7.0.0/16 
        in label:    17        
        out label:   imp-null  lsr:14.14.14.14:0   
  30.10.0.0/16 
        in label:    5016      
        out label:   269       lsr:14.14.14.14:0   
  30.13.0.0/16 
        in label:    76        
        out label:   imp-null  lsr:14.14.14.14:0 

Table 22 describes the significant fields in the sample display shown above.

Table 22 show mpls ip binding Command Field Descriptions 

Field
Description
a.b.c.d/n

Destination prefix. Indicates that the following lines are for a particular destination (network/mask).

in label

Incoming label. This is the local label assigned by the LSR and advertised to other LSRs. The label value imp-null indicates the well-known Implicit NULL label.

out label

Outgoing label. This is a remote label learned from an LDP neighbor. The neighbor is identified by its LDP ID in the lsr field.

inuse

Indicates that the outgoing label is in use for MPLS forwarding, that is, it is installed in the MPLS forwarding table (LFIB).

in vc label

Incoming MPLS ATM label. This is the local VPI/VCI assigned by the LSR as the incoming label for the destination and advertised to the upstream LSR(s).

out vc label

Outgoing MPLS ATM label. This is the VPI/VCI learned from the destination next hop as its label for the destination and advertised to this LSR.

ATM1/0.8

The ATM interface with which the MPLS ATM label is associated.

Active

The state of the label VC (LVC) associated with the destination prefix. Options include the following:

Active. The label VC is established and operational.

Bindwait. Waiting for a response from the destination next hop.

Remote Resource Wait. Waiting for resources (VPI/VCI) to become available on the destination next hop.

Parent Wait. Transit LVC upstream side waiting for downstream side to become active.

AbortAckWait. Waiting for response to a Label Abort message sent to the destination next hop.

ReleaseWait. Waiting for response to a Label Withdraw message sent to an upstream neighbor.

vcd n

Virtual circuit descriptor number for the LVC.

ingress n hops

Indicates whether the LSR is an ingress, transit, or egress node for the destination. Options include the following:

Ingress n hops. The LSR is an ingress edge router for the MPLS ATM cloud for the destination.

Egress. The LSR is an egress edge router for the MPLS ATM cloud for the destination.

Transit. The LSR is a transit LSR within the MPLS ATM cloud for the destination.


In the following example, summary information about the label bindings learned by LDP is shown:

Router# show mpls ip binding summary 
Total number of prefixes: 53
 
Generic label bindings
                      assigned        learned
       prefixes      in labels     out labels
             53             53             51
 
ATM label bindings summary
      interface   total  active   local  remote   Bwait   Rwait  IFwait
       ATM1/0.8      47      47      40       7       0       0       0
Router#

Table 23 describes the significant fields in the sample display shown above.

Table 23 show mpls ip binding summary Command Field Descriptions 

Field
Description
Total number of 
prefixes

The number of destinations for which the LSR has label bindings.

Generic label 
bindings

Indicates the start of summary information for "generic" label bindings. Generic labels are used for MPLS forwarding on all interface types except MPLS ATM interfaces.

prefixes

The number of destinations for which the LSR has a generic label binding.

assigned in labels

The number of prefixes for which the LSR has assigned an incoming (local) label.

learned out labels

The number of prefixes for which the LSR has learned an outgoing (remote) label from an LDP neighbor.

ATM label bindings 
summary

Indicates the start of summary information for MPLS ATM label bindings. An ATM label is a VPI/VCI.

interface

Indicates a row in the ATM label bindings summary table. The summary information in the row is for ATM labels associated with this interface.

total

The total number of ATM labels associated with the interface.

active

The number of ATM labels (LVCs) in the Active (operational) state.

local

The number of ATM labels assigned by this LSR for the interfaces. These are incoming labels.

remote

The number of ATM labels learned from the neighbor LSR for this interface. These are outgoing labels.

Bwait

The number of bindings (LVCs) waiting for a label assignment from the neighbor LSR for the interface.

Rwait

The number of bindings (LVCs) waiting for resources (VPI/VCIs) to become available on the neighbor LSR for the interface.

IFWait

The number of bindings (LVCs) waiting for labels to be installed for switching use.


Related Commands

Command
Description

show mpls ldp bindings

Displays the contents of the label information base (LIB).

show mpls atm-ldp bindings

Displays specified entries from the ATM label binding database.


show mpls ldp backoff

To display information about the configured session setup backoff parameters and any potential LDP peers with which session setup attempts are being throttled, use the show mpls ldp backoff command in privileged EXEC mode.

show mpls ldp backoff

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.0(10)ST

This command was introduced.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Examples

The following shows sample output from the show mpls ldp backoff command.

Router# show mpls ldp backoff 

LDP initial/maximum backoff: 30/240 sec
Backoff table: 2 entries
LDP Id              Backoff(sec)   Waiting(sec)     
144.0.0.44:0        60             30               
155.0.0.55:0        120            90               

Table 24 describes the significant fields in the sample display shown above.

Table 24 show mpls ldp backoff Command Field Descriptions 

Field
Description
LDP initial/maximum 
backoff

Indicates the configured backoff parameters in seconds.

Backoff table

Contains a list of discovered LDP neighbors for which session setup is being delayed because of previous failures to establish a session due to incompatible configuration. The backoff table incorporates the following information:

LDP Id—Identifies the LDP neighbors

Backoff (sec)—Shows the amount of time that session setup is being delayed

Waiting (sec)—Shows the approximate amount of time that session setup has been delayed


Related Commands

Command
Description

mpls ldp backoff

Configures session setup delay parameters for the LDP backoff mechanism.


show mpls ldp bindings

To display the contents of the label information base (LIB), use the show mpls ldp bindings command in privileged EXEC mode:

show mpls ldp bindings [vrf vpn-name] [network {mask | length} [longer-prefixes]]
[
local-label label  [- label]] [remote-label label [- label]] [neighbor address] [local]

Syntax Description

vrf vpn-name

(Optional) Displays the label bindings for the specified VPN routing/forwarding instance (vpn-name).

network

(Optional) Defines the destination network number.

mask

Specifies the network mask, written as A.B.C.D.

length

Specifies the mask length (1 to 32 characters).

longer-prefixes

(Optional) Selects any prefix that matches mask with a length from 1 to 32 characters.

local-label label - label

(Optional) Display entries matching local label values. Use the label - label argument to indicate the label range.

remote-label label - label

(Optional) Displays entries matching the label values assigned by a neighbor router. Use the label - label argument to indicate the label range.

neighbor address

(Optional) Displays the label bindings assigned by the selected neighbor.

local

(Optional) Displays the local label bindings.


Defaults

If no optional keyword or parameter is supplied, the command displays the label information base (LIB) for the default routing domain only.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The show mpls ldp bindings command displays label bindings learned by LDP or TDP.

A request can specify that the entire database be displayed, or that the display be limited to a subset of entries according to the following:

Prefix

Input or output label values or ranges

Neighbor advertising the label


Note The command show mpls ip binding includes the output generated by the show mpls ldp bindings command, as well as information about label bindings for LC-ATM interfaces.


Examples

The following shows sample output from the show mpls ldp bindings command. This form of the displays the contents of the label information base (LIB) for the default routing domain.

Router# show mpls ldp bindings
34.0.0.0/8, rev 9
        local binding:  label: imp-null
        remote binding: lsr: 155.0.0.55:0, label: 17
        remote binding: lsr: 66.66.0.66:0, label: 18
        remote binding: lsr: 144.0.0.44:0, label: imp-null
  45.0.0.0/8, rev 17
        local binding:  label: 19
        remote binding: lsr: 155.0.0.55:0, label: imp-null
        remote binding: lsr: 66.66.0.66:0, label: 16
        remote binding: lsr: 144.0.0.44:0, label: imp-null
  66.66.0.66/32, rev 19
        local binding:  label: 20
        remote binding: lsr: 155.0.0.55:0, label: 19
        remote binding: lsr: 66.66.0.66:0, label: imp-null
        remote binding: lsr: 144.0.0.44:0, label: 18
  103.0.0.0/8, rev 11
        local binding:  label: imp-null
  130.77.0.0/16, rev 23
        local binding:  label: 22
        remote binding: lsr: 155.0.0.55:0, label: 22
        remote binding: lsr: 144.0.0.44:0, label: 21
        remote binding: lsr: 66.66.0.66:0, label: 20
  140.66.0.0/16, rev 96
        remote binding: lsr: 66.66.0.66:0, label: imp-null
  155.0.0.55/32, rev 29
        local binding:  label: 25
        remote binding: lsr: 155.0.0.55:0, label: imp-null
        remote binding: lsr: 144.0.0.44:0, label: 24
        remote binding: lsr: 66.66.0.66:0, label: 24
  166.45.0.0/16, rev 33
        local binding:  label: 27
        remote binding: lsr: 155.0.0.55:0, label: imp-null
        remote binding: lsr: 66.66.0.66:0, label: 26
        remote binding: lsr: 144.0.0.44:0, label: 26
  166.46.0.0/16, rev 35
        local binding:  label: 28
        remote binding: lsr: 155.0.0.55:0, label: imp-null
        remote binding: lsr: 66.66.0.66:0, label: 27
        remote binding: lsr: 144.0.0.44:0, label: 27
  . . .

The following is sample output from the show mpls ldp bindings 166.0.0.0 8 longer-prefixes neighbor 144.0.0.44 variant of the command; it displays labels learned from LSR 144.0.0.44 for network 166.0.0.0 and any of its subnets. The use of the neighbor option suppresses the output of local labels and labels learned from other neighbors.

Router# show mpls ldp bindings 166.0.0.0 8 longer-prefixes neighbor 144.0.0.44
  166.44.0.0/16, rev 31
        remote binding: lsr: 144.0.0.44:0, label: 25
  166.45.0.0/16, rev 33
        remote binding: lsr: 144.0.0.44:0, label: 26
  166.245.0.0/16, rev 71
        remote binding: lsr: 144.0.0.44:0, label: 45
  166.246.0.0/16, rev 73
        remote binding: lsr: 144.0.0.44:0, label: 46
. 
. 
.

The following shows sample output from the show mpls ldp bindings vrf vpn1 command, which displays the label bindings for the specified VPN routing/forwarding instance named vpn1.

Router# show mpls ldp bindings vrf vpn1
3.3.0.0/16, rev 164
        local binding: label:117
        remote binding:lsr:14.14.14.14:0, label:imp-null
  13.13.13.13/32, rev 1650
        local binding: label:1372
        remote binding:lsr:14.14.14.14:0, label:268
  14.14.14.14/32, rev 165
        local binding: label:118
        remote binding:lsr:14.14.14.14:0, label:imp-null
  15.15.15.15/32, rev 1683
        local binding: label:1370
        remote binding:lsr:14.14.14.14:0, label:266
  16.16.16.16/32, rev 775
        local binding: label:8370
        remote binding:lsr:14.14.14.14:0, label:319
  18.18.18.18/32, rev 1655
        local binding: label:21817
        remote binding:lsr:14.14.14.14:0, label:571
  30.2.0.0/16, rev 1653
        local binding: label:6943
        remote binding:lsr:14.14.14.14:0, label:267
  30.3.0.0/16, rev 413
        local binding: label:2383
        remote binding:lsr:14.14.14.14:0, label:imp-null
  30.4.0.0/16, rev 166
        local binding: label:77
        remote binding:lsr:14.14.14.14:0, label:imp-null
  30.5.0.0/16, rev 1429
        local binding: label:20715
        remote binding:lsr:14.14.14.14:0, label:504
  30.7.0.0/16, rev 4
        local binding: label:17
        remote binding:lsr:14.14.14.14:0, label:imp-null
  30.10.0.0/16, rev 422
        local binding: label:5016
        remote binding:lsr:14.14.14.14:0, label:269
. 
. 
. 

Table 25 describes the significant fields in the sample display shown above.

Table 25 show mpls ldp bindings Command Field Descriptions 

Field
Description
a.b.c.d/n

The IP prefix and mask for a particular destination (network/mask).

rev

A revision number (rev) that is used internally to manage label distribution for this destination.

remote binding

A list of outgoing labels for this destination learned from other LSRs. Each item in this list identifies the LSR from which the outgoing label was learned and the label itself. The LSR is identified by its LDP identifier.


Related Commands

Command
Description

show mpls ldp neighbor

Displays the status of LDP sessions.


show mpls ldp discovery

To display the status of the LDP discovery process, use the show mpls ldp discovery command in privileged EXEC mode. This command generates a list of interfaces over which the LDP discovery process is running.

show mpls ldp discovery [vrf vpn-name]

show mpls ldp discovery [all]

Syntax Description

vrf vpn-name

(Optional) Displays the neighbor discovery information for the specified VPN routing/forwarding instance (vpn-name).

all

(Optional) When the all keyword is specified alone in this command, the command displays LDP discovery information for all VPNs, including those in the default routing domain.


Defaults

This command displays neighbor discovery information for the default routing domain if an optional argument is not specified.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

This command displays neighbor discovery information for LDP or TDP.

Examples

The following shows sample output from the show mpls ldp discovery command.

Router# show mpls ldp discovery

Local LDP Identifier:
    8.1.1.1:0
Discovery Sources:
    Interfaces:
        Ethernet1/1/3 (ldp): xmit/recv
            LDP Id: 177.73.0.77:0
            LDP Id: 144.0.0.44:0
            LDP Id: 155.0.0.55:0
        ATM3/0.1 (ldp): xmit/recv
            LDP Id: 203.0.7.7:2
        ATM0/0.2 (tdp): xmit/recv
            TDP Id: 119.1.0.1:1
Targeted Hellos:
        8.1.1.1 -> 133.0.0.33 (ldp): active, xmit/recv
            LDP Id: 133.0.0.33:0
        8.1.1.1 -> 168.7.0.16 (tdp): passive, xmit/recv
            TDP Id: 133.0.0.33:0
Router#

The following shows sample output from the show mpls ldp discovery all command, which shows the interfaces engaged in LDP discovery activity for all the VPN routing/forwarding instances, including those in the default routing domain. In this example, note that the same neighbor LDP Id (14.14.14.14) appears in all the listed VRF interfaces, highlighting the fact that the same IP address can coexist in different VPN routing/forwarding instances.

Router# show mpls ldp discovery all 
Local LDP Identifier:
    12.12.12.12:0
    Discovery Sources:
    Interfaces:
        ATM1/1/0.1 (tdp):xmit/recv
            TDP Id:11.11.11.11:0
VRF vpn1:Local LDP Identifier:
    30.7.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.1 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn2:Local LDP Identifier:
    30.13.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.2 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn3:Local LDP Identifier:
    30.15.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.3 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn4:Local LDP Identifier:
    30.17.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.4 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn5:Local LDP Identifier:
    30.19.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.5 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn6:Local LDP Identifier:
    30.21.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.6 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn7:Local LDP Identifier:
    30.23.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.7 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn8:Local LDP Identifier:
    30.25.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.8 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn9:Local LDP Identifier:
    30.27.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.9 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn10:Local LDP Identifier:
    30.29.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.10 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn11:Local LDP Identifier:
    30.31.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.11 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn12:Local LDP Identifier:
    30.33.0.2:0
    Discovery Sources:
    Interfaces:
        ATM3/0/0.12 (ldp):xmit/recv
            LDP Id:14.14.14.14:0
VRF vpn13:Local LDP Identifier:
          
Router#

Table 26 describes the significant fields in the sample display shown above.

Table 26 show mpls ldp discovery Command Field Descriptions 

Field
Description
Local LDP Identifier

The LDP identifier for the local router. An LDP identifier is a 6-byte construct displayed in the form "IP address:number."

By convention, the first 4 bytes of the LDP identifier constitute the router ID; integers, starting with 0, constitute the final two bytes of the IP address:number construct.

Interfaces

Lists the interfaces that are engaging in LDP discovery activity, described below:

The xmit field—Indicates that the interface is transmitting LDP discovery Hello packets.

The recv field—Indicates that the interface is receiving LDP discovery Hello packets.

The (ldp) or (tdp) field—Indicates the label distribution protocol configured for the interface.

The LDP (or TDP) identifiers indicate the LDP (or TDP) neighbors discovered on the interface.

Targeted Hellos

Lists the platforms to which targeted Hello messages are being sent, as described below:

The xmit, recv, (ldp), and (tdp) fields are as described above for the Interfaces field.

The active field indicates that this LSR has initiated targeted Hello messages.

The passive field indicates that the neighbor LSR has initiated targeted Hello messages and that this LSR is configured to respond to the targeted Hello messages from the neighbor.


Note The entry for a given target platform may indicate both active and passive.



Related Commands

Command
Description

show mpls ldp neighbor

Displays the status of LDP sessions.

show mpls interfaces

Displays information about one or more interfaces that have been configured for label switching.

mpls label protocol (global configuration)

Specifies the label distribution protocol (LDP or TDP) to be used on a platform.

mpls label protocol (interface configuration)

Specifies the label distribution protocol (LDP or TDP) to be used on a given interface.


show mpls ldp neighbor

To display the status of LDP sessions, issue the show mpls ldp neighbor command in privileged EXEC mode.

show mpls ldp neighbor [vrf vpn-name] [address | interface] [detail]

show mpls ldp neighbor [all]

Syntax Description

vrf vpn-name

(Optional) Displays the LDP neighbors for the specified VPN routing/forwarding instance (vpn-name).

address

(Optional) Identifies the neighbor with this IP address.

interface

(Optional) Defines the LDP neighbors accessible over this interface.

detail

(Optional) Displays information in long form.

all

(Optional) When the all keyword is specified alone in this command, the command displays LDP neighbor information for all VPNs, including those in the default routing domain.


Defaults

This command displays information about LDP neighbors for the default routing domain if the optional vrf keyword is not specified.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.0(14)ST

This command was modified to reflect MPLS VPN support for LDP.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Usage Guidelines

The show mpls ldp neighbor command can provide information about all LDP neighbors, or the information can be limited to the following:

Neighbor with specific IP address

LDP neighbors known to be accessible over a specific interface


Note This command displays information about LDP and TDP neighbor sessions.


Examples

The following shows sample output from the show mpls ldp neighbor command:

Router# show mpls ldp neighbor
Peer LDP Ident: 203.0.7.7:2; Local LDP Ident 8.1.1.1:1
        TCP connection: 203.0.7.7.11032 - 8.1.1.1.646
        State: Oper; Msgs sent/rcvd: 5855/6371; Downstream on demand
        Up time: 13:15:09
        LDP discovery sources:
          ATM3/0.1
Peer LDP Ident: 7.1.1.1:0; Local LDP Ident 8.1.1.1:0
        TCP connection: 7.1.1.1.646 - 8.1.1.1.11006
        State: Oper; Msgs sent/rcvd: 4/411; Downstream
        Up time: 00:00:52
        LDP discovery sources:
          Ethernet1/0/0
        Addresses bound to peer LDP Ident:
          2.0.0.29        7.1.1.1         59.0.0.199      212.10.1.1
          10.205.0.9      
Router#

The following shows sample output from the show mpls ldp neighbor vrf vpn10 command, which displays the LDP neighbor information for the specified VPN routing/forwarding instance named vpn10:

Router# show mpls ldp neighbor vrf vpn10
Peer LDP Ident:14.14.14.14:0; Local LDP Ident 30.29.0.2:0
        TCP connection:14.14.14.14.646 - 30.29.0.2.11384
        State:Oper; Msgs sent/rcvd:1423/800; Downstream
        Up time:02:38:11
        LDP discovery sources:
          ATM3/0/0.10
        Addresses bound to peer LDP Ident:
          3.3.36.9        30.7.0.1        14.14.14.14     30.13.0.1       
          30.15.0.1       30.17.0.1       30.19.0.1       30.21.0.1       
          30.23.0.1       30.25.0.1       30.27.0.1       30.29.0.1       
          30.31.0.1       30.33.0.1       30.35.0.1       30.37.0.1       
          30.39.0.1       30.41.0.1       30.43.0.1       30.45.0.1       
          30.47.0.1       30.49.0.1       30.51.0.1       30.53.0.1       
          30.55.0.1       30.57.0.1       30.59.0.1       30.61.0.1       
          30.63.0.1       30.65.0.1       30.67.0.1       30.69.0.1       
          30.71.0.1       30.73.0.1       30.75.0.1       30.77.0.1       
          30.79.0.1       30.81.0.1       30.83.0.1       30.85.0.1       
          30.87.0.1       30.89.0.1       30.91.0.1       30.93.0.1       
          30.95.0.1       30.97.0.1       30.99.0.1       30.101.0.1      
          30.103.0.1      30.105.0.1      30.107.0.1      30.109.0.1      
          30.4.0.2        30.3.0.2        
Router#

The following shows sample output from the show mpls ldp neighbor all command, which displays the LDP neighbor information for all VPN routing/forwarding instances, including those in the default routing domain. In this example, note that the same neighbor LDP Id (14.14.14.14) appears in all the listed VRF interfaces, highlighting the fact that the same IP address can coexist in different VPN routing/forwarding instances.

Router# show mpls ldp neighbor all 
Peer TDP Ident:11.11.11.11:0; Local TDP Ident 12.12.12.12:0
        TCP connection:11.11.11.11.711 - 12.12.12.12.11003
        State:Oper; PIEs sent/rcvd:185/187; Downstream
        Up time:02:40:02
        TDP discovery sources:
          ATM1/1/0.1
        Addresses bound to peer TDP Ident:
          3.3.38.3        30.1.0.2        11.11.11.11     
VRF vpn1:
    Peer LDP Ident:14.14.14.14:0; Local LDP Ident 30.7.0.2:0
        TCP connection:14.14.14.14.646 - 30.7.0.2.11359
        State:Oper; Msgs sent/rcvd:952/801; Downstream
        Up time:02:38:49
        LDP discovery sources:
          ATM3/0/0.1
        Addresses bound to peer LDP Ident:
          3.3.36.9        30.7.0.1        14.14.14.14     30.13.0.1       
          30.15.0.1       30.17.0.1       30.19.0.1       30.21.0.1       
          30.23.0.1       30.25.0.1       30.27.0.1       30.29.0.1       
          30.31.0.1       30.33.0.1       30.35.0.1       30.37.0.1       
          30.39.0.1       30.41.0.1       30.43.0.1       30.45.0.1       
          30.47.0.1       30.49.0.1       30.51.0.1       30.53.0.1       
          30.55.0.1       30.57.0.1       30.59.0.1       30.61.0.1       
          30.63.0.1       30.65.0.1       30.67.0.1       30.69.0.1       
          30.71.0.1       30.73.0.1       30.75.0.1       30.77.0.1       
          30.79.0.1       30.81.0.1       30.83.0.1       30.85.0.1       
          30.87.0.1       30.89.0.1       30.91.0.1       30.93.0.1       
          30.95.0.1       30.97.0.1       30.99.0.1       30.101.0.1      
          30.103.0.1      30.105.0.1      30.107.0.1      30.109.0.1      
          30.4.0.2        30.3.0.2        
VRF vpn2:
    Peer LDP Ident:14.14.14.14:0; Local LDP Ident 30.13.0.2:0
        TCP connection:14.14.14.14.646 - 30.13.0.2.11361
        State:Oper; Msgs sent/rcvd:964/803; Downstream
        Up time:02:38:50
        LDP discovery sources:
          ATM3/0/0.2
        Addresses bound to peer LDP Ident:
          3.3.36.9        30.7.0.1        14.14.14.14     30.13.0.1       
          30.15.0.1       30.17.0.1       30.19.0.1       30.21.0.1       
          30.23.0.1       30.25.0.1       30.27.0.1       30.29.0.1       
          30.31.0.1       30.33.0.1       30.35.0.1       30.37.0.1       
          30.39.0.1       30.41.0.1       30.43.0.1       30.45.0.1       
          30.47.0.1       30.49.0.1       30.51.0.1       30.53.0.1       
          30.55.0.1       30.57.0.1       30.59.0.1       30.61.0.1       
          30.63.0.1       30.65.0.1       30.67.0.1       30.69.0.1       
          30.71.0.1       30.73.0.1       30.75.0.1       30.77.0.1       
          30.79.0.1       30.81.0.1       30.83.0.1       30.85.0.1       
          30.87.0.1       30.89.0.1       30.91.0.1       30.93.0.1       
          30.95.0.1       30.97.0.1       30.99.0.1       30.101.0.1      
          30.103.0.1      30.105.0.1      30.107.0.1      30.109.0.1      
          30.4.0.2        30.3.0.2        
VRF vpn3:
    Peer LDP Ident:14.14.14.14:0; Local LDP Ident 30.15.0.2:0
        TCP connection:14.14.14.14.646 - 30.15.0.2.11364
        State:Oper; Msgs sent/rcvd:1069/800; Downstream
        Up time:02:38:52
        LDP discovery sources:
          ATM3/0/0.3
        Addresses bound to peer LDP Ident:
          3.3.36.9        30.7.0.1        14.14.14.14     30.13.0.1       
          30.15.0.1       30.17.0.1       30.19.0.1       30.21.0.1       
          30.23.0.1       30.25.0.1       30.27.0.1       30.29.0.1       
          30.31.0.1       30.33.0.1       30.35.0.1       30.37.0.1       
          30.39.0.1       30.41.0.1       30.43.0.1       30.45.0.1       
          30.47.0.1       30.49.0.1       30.51.0.1       30.53.0.1       
          30.55.0.1       30.57.0.1       30.59.0.1       30.61.0.1       
          30.63.0.1       30.65.0.1       30.67.0.1       30.69.0.1       
          30.71.0.1       30.73.0.1       30.75.0.1       30.77.0.1       
          30.79.0.1       30.81.0.1       30.83.0.1       30.85.0.1       
          30.87.0.1       30.89.0.1       30.91.0.1       30.93.0.1       
          30.95.0.1       30.97.0.1       30.99.0.1       30.101.0.1      
          30.103.0.1      30.105.0.1      30.107.0.1      30.109.0.1      
          30.4.0.2        30.3.0.2        
VRF vpn4:
    Peer LDP Ident:14.14.14.14:0; Local LDP Ident 30.17.0.2:0
        TCP connection:14.14.14.14.646 - 30.17.0.2.11366
        State:Oper; Msgs sent/rcvd:1199/802; Downstream
          
Router#

Table 27 describes the significant fields in the sample display shown above.

Table 27 show mpls ldp neighbor Command Field Descriptions 

Field
Description
Peer LDP Ident

The LDP identifier of the neighbor (peer) for this session.

Local LDP Ident

The LDP identifier for the local LSR for this session.

TCP connection

The TCP connection used to support the LDP session, shown in the following format:

peer IP address.peer port

local IP address.local port

State

The state of the LDP session. Generally this is Oper (operational), but transient is another possible state.

Msgs sent/rcvd

The number of LDP messages sent to and received from the session peer. The count includes the transmission and receipt of periodic keepalive messages, which are required for maintenance of the LDP session.

Downstream on demand

Indicates that the Downstream on Demand method of label distribution is being used for this LDP session. When the Downstream on Demand method is used, an LSR advertises its locally assigned (incoming) labels to its LDP peer only when the peer asks for them.

Downstream

Indicates that the downstream method of label distribution is being used for this LDP session. When the downstream method is used, an LSR advertises all of its locally assigned (incoming) labels to its LDP peer (subject to any configured access list restrictions).

Up time

The length of time the LDP session has existed.

LDP discovery sources

The source(s) of LDP discovery activity that led to the establishment of this LDP session.

Addresses bound to 
peer LDP Ident

The known interface addresses of the LDP session peer. These are addresses that might appear as "next hop" addresses in the local routing table. They are used to maintain the Label Forwarding Information Base (LFIB).


Related Commands

Command
Description

show mpls ldp discovery

Displays the status of the LDP discovery process.


show mpls ldp parameters

To display current LDP parameters, use the show mpls ldp parameters command in privileged EXEC mode.

show mpls ldp parameters

Syntax Description

This command has no optional keywords or arguments.

Defaults

This command has no default behavior or values.

Command Modes

Privileged EXEC

Command History

Release
Modification

11.1CT

This command was introduced.

12.0(10)ST

This command was modified to reflect MPLS IETF command syntax and terminology.

12.1(8a)E

This command was integrated into Cisco IOS Release 12.1(8a)E.

12.2(11)S

This command was integrated into Cisco IOS Release 12.2(11)S.


Examples

The following shows sample output from the show mpls ldp parameters command:

Router# show mpls ldp parameters
Protocol version: 1
Downstream label pool: min label 16; max label 100000
Session hold time: 180 sec; keep alive interval: 60 sec
Discovery hello: holdtime: 15 sec; interval: 5 sec
Discovery targeted hello: holdtime: 180 sec; interval: 5 sec
LDP for targeted sessions; peer acl: 1
LDP initial/maximum backoff: 30/240 sec
Router# 

Table 28 describes the significant fields in the sample display above.

Table 28 show mpls ldp parameters Command Field Descriptions 

Field
Description
Protocol version

Indicates the version of LDP running on the platform.

Downstream label pool

Describes the range of labels available for the platform to assign for label switching purposes. The available labels range from the smallest label value (min label) to the largest label value (max label), with a modest number of labels at the low end of the range (reserved labels) reserved for diagnostic purposes.

Session hold time

Indicates the time that an LDP session is to be maintained with an LDP peer without receiving LDP traffic or an LDP keepalive message from the peer.

keep alive interval

Indicates the interval of time between consecutive transmissions of LDP keepalive messages to an LDP peer.

Discovery hello

Indicates the amount of time to remember that a neighbor platform wants an LDP session without receiving an LDP Hello message from the neighbor (hold time), and the time interval between the transmission of consecutive LDP Hello messages to neighbors (interval).

Discovery targeted 
hello

Indicates the amount of time to remember that a neighbor platform wants an LDP session when:

1. The neighbor platform is not directly connected to the router.

2. The neighbor platform has not sent an LDP Hello message. This intervening interval is known as hold time.

Also indicates the time interval between the transmission of consecutive Hello messages to a neighbor not directly connected to the router.

LDP for targeted 
sessions

Reports the parameters that have been set by the show mpls atm-ldp bindings command.

LDP initial/maximum 
backoff

Reports the parameters that have been set by the mpls ldp backoff command.


Related Commands

Command
Description

show mpls atm-ldp bindings

Configures the interval between transmission of LDP discovery Hello messages.

mpls ldp holdtime

Configures keepalive message hold time for LDP sessions.


Glossary

ATM-LSR—A label switch router with a number of LC-ATM interfaces. The router forwards the cells among these interfaces using labels carried in the VPI/VCI field of the ATM cell header.

ATM edge LSR—A router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The ATM edge LSR adds labels to unlabeled packets and strips labels from labeled packets.

CoS—Class of service. A feature that provides scalable, differentiated types of service across an MPLS network.

label—A short fixed-length label that tells switching nodes how to forward data (packets or cells).

label-controlled ATM interface (LC-ATM interface)—An interface on a router or switch that uses label distribution procedures to negotiate label VCs.

label edge router (LER)—A router that performs label imposition.

label imposition—The action of putting the first label on a packet.

Label switch—A node that forwards units of data (packets or cells) on the basis of labels.

label-switched path (LSP)—A sequence of hops (Router 0...Router n) in which a packet travels from R0 to Rn by means of label switching mechanisms. A label-switched path can be chosen dynamically, based on normal routing mechanisms, or it can be configured manually.

label-switched path (LSP) tunnel—A configured connection between two routers, in which label switching techniques are used for packet forwarding.

Label switching router (LSR)—A Layer 3 router that forwards a packet based on the value of a label encapsulated in the packet.

Label VC (LVC)—An ATM virtual circuit that is set up through ATM LSR label distribution procedures.

LDP—Label distribution protocol. The protocol used to distribute label bindings to LSRs.

LFIB—Label forwarding information base. The data structure used by switching functions to switch labeled packets.

LIB—Label information base. A database used by an LSR to store labels learned from other LSRs, as well as labels assigned by the local LSR.

MPLS—Multiprotocol label switching. An emerging industry standard that defines support for MPLS forwarding of packets along normally routed paths (sometimes called MPLS hop-by-hop forwarding).

tailend—The downstream, received end of a tunnel.

traffic engineering—The techniques and processes used to cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods had been applied.

traffic engineering tunnel—A label-switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different from the one that Layer 3 routing would cause the tunnel to take.