Cisco Release 12.4 User Manual

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

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C O N T E N T S

MPLS Label Distribution Protocol (LDP)

1

Finding Feature Information 1 Prerequisites for MPLS LDP 1 Information About MPLS LDP 1

Introduction to MPLS LDP 2 MPLS LDP Functional Overview 2 LDP and TDP Support 2 Introduction to LDP Sessions 3

Directly Connected MPLS LDP Sessions 3 Nondirectly Connected MPLS LDP Sessions 4

Introduction to LDP Label Bindings Label Spaces and LDP Identifiers 4

How to Configure MPLS LDP 5

Enabling Directly Connected LDP Sessions 6 Establishing Nondirectly Connected MPLS LDP Sessions 8 Saving Configurations MPLS Tag Switching Commands 11 Specifying the LDP Router ID 12 Preserving QoS Settings with MPLS LDP Explicit Null 14 Protecting Data Between LDP Peers with MD5 Authentication 18

MPLS LDP Configuration Examples 21

Configuring Directly Connected MPLS LDP Sessions Example 21

Establishing Nondirectly Connected MPLS LDP Sessions Example 23 Additional References 25 Feature Information for MPLS Label Distribution Protocol 26

MPLS LDP Session Protection 31

Finding Feature Information 31 Restrictions for MPLS LDP Session Protection 31 Information About MPLS LDP Session Protection 31

MPLS LDP Session Protection Customizations 32 How to Configure MPLS LDP Session Protection 33

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Contents

Enabling MPLS LDP Session Protection 33

Verifying MPLS LDP Session Protection 35

Troubleshooting Tips 36 Configuration Examples for MPLS LDP Session Protection 36 Additional References 39 Command Reference 40

MPLS LDP Inbound Label Binding Filtering 41

Finding Feature Information 41 Restrictions 41 Information about MPLS LDP Inbound Label Binding Filtering 41 How to Configure MPLS LDP Inbound Label Binding Filtering 42

Configuring MPLS LDP Inbound Label Binding Filtering 42

Verifying that MPLS LDP Inbound Label Bindings are Filtered 44 Configuration Examples for MPLS LDP Inbound Label Binding Filtering 45 Additional References 46 Feature Information for MPLS LDP Inbound Label Binding Filtering Feature 47 Glossary 48

MPLS LDP Autoconfiguration 51

Finding Feature Information 51 Restrictions for MPLS LDP Autoconfiguration 51 Information About MPLS LDP Autoconfiguration 52

MPLS LDP Autoconfiguration on OSPF and IS-IS Interfaces 52 How to Configure MPLS LDP Autoconfiguration 52

Configuring MPLS LDP Autoconfiguration with OSPF Interfaces 52

Disabling MPLS LDP Autoconfiguration from Selected OSPF Interfaces 54

Verifying MPLS LDP Autoconfiguration with OSPF 55

Configuring MPLS LDP Autoconfiguration with IS-IS Interfaces 57

Disabling MPLS LDP Autoconfiguration from Selected IS-IS Interfaces 59

Verifying MPLS LDP Autoconfiguration with IS-IS 60

Troubleshooting Tips 61

Configuration Examples for MPLS LDP Autoconfiguration 61

MPLS LDP Autoconfiguration with OSPF Example 61

MPLS LDP Autoconfiguration with IS-IS Examples 62 Additional References 62 Feature Information for MPLS LDP Autoconfiguration 63

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Contents

MPLS LDP Graceful Restart 65

Finding Feature Information 65 Restrictions 65 Information About MPLS LDP Graceful Restart 66

How MPLS LDP Graceful Restart Works 66

How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart 67

What Happens If a Route Processor Does Not Have LDP Graceful Restart 67 How to Configure MPLS LDP Graceful Restart 67

Configuring MPLS LDP Graceful Restart 67

Verifying the Configuration 69 Configuration Example for MPLS LDP Graceful Restart 69 Additional References 72 Feature Information for MPLS LDP Graceful Restart 73

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Contents

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MPLS LDP Configuration Guide, Cisco IOS Release 12.4

MPLS Label Distribution Protocol (LDP)

Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) enables peer label switch routers (LSRs) in an MPLS network to exchange label binding information for supporting hop-by-hop forwarding in an MPLS network. This module explains the concepts related to MPLS LDP and describes how to configure MPLS LDP in a network.

• Finding Feature Information, page 1

• Prerequisites for MPLS LDP, page 1

• Information About MPLS LDP, page 1

• How to Configure MPLS LDP, page 5

• MPLS LDP Configuration Examples, page 21

• Additional References, page 25

• Feature Information for MPLS Label Distribution Protocol, page 26

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for MPLS LDP

Label switching on a router requires that Cisco Express Forwarding (CEF) be enabled on that router.

Information About MPLS LDP

• Introduction to MPLS LDP, page 2

• MPLS LDP Functional Overview, page 2

• LDP and TDP Support, page 2

• Introduction to LDP Sessions, page 3

• Introduction to LDP Label Bindings Label Spaces and LDP Identifiers, page 4

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Information About MPLS LDP

Introduction to MPLS LDP

MPLS LDP provides the means for 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.

MPLS LDP enables one LSR to inform another LSR of the label bindings it has made. Once a pair of routers communicate the LDP parameters, they establish a label-switched path (LSP). MPLS LDP enables LSRs to distribute labels along normally routed paths to support MPLS forwarding. This method of label distribution is also called hop-by-hop forwarding. With IP forwarding, when a packet arrives at a router the router looks at the destination address in the IP header, performs a route lookup, and forwards the packet to the next hop. With MPLS forwarding, when a packet arrives at a router the router looks at the incoming label, looks up the label in a table, and then forwards the packet to the next hop. MPLS LDP is useful for applications that require hop-by-hop forwarding, such as MPLS VPNs.

MPLS LDP Functional Overview

Cisco MPLS LDP provides the building blocks for MPLS-enabled applications, such as MPS Virtual Private Networks (VPNs).

Introduction to MPLS LDP

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 (LSPs), forward label traffic across an MPLS backbone to particular destinations. These capabilities enable service providers to implement MPLS-based IP VPNs and IP+ATM services across multivendor MPLS networks.

LDP and TDP Support

LDP supercedes Tag Distribution Protocol (TDP). See the table below for information about LDP and TDP support in Cisco IOS releases.

Use caution when upgrading the image on a router that uses TDP. Ensure that the TDP sessions are established when the new image is loaded. You can accomplish this by issuing the global configuration command mpls label protocol tdp. Issue this command and save it to the startup configuration before loading the new image. Alternatively, you can enter the command and save the running configuration immediately after loading the new image.

Table 1

Train and Release LDP/TDP Support

12.0S Train

LDP and TDP Support

• TDP is enabled by default.

• Cisco IOS Release 12.0(29)S and earlier releases: TDP is supported for LDP features.

• Cisco IOS Release 12.0(30)S and later releases: TDP is not support for LDP features.

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Introduction to LDP Sessions

Train and Release LDP/TDP Support

Directly Connected MPLS LDP Sessions

12.2S, SB, and SR Trains

12.T/Mainline Trains

Introduction to LDP Sessions

When you enable MPLS LDP, the LSRs send out messages to try to find other LSRs with which they can create LDP sessions. The following sections explain the differences between directly connected LDP sessions and nondirectly connected LDP sessions.

• Directly Connected MPLS LDP Sessions, page 3

• Nondirectly Connected MPLS LDP Sessions, page 4

• LDP is enabled by default.

• Cisco IOS Release 12.2(25)S and earlier releases: TDP is

supported for LDP features.

• Cisco IOS Releases 12.2(27)SBA, 12.2(27)SRA,

12.2(27)SRB and later releases: TDP is not supported for LDP features.

• Cisco IOS Release 12.3(14)T and earlier releases: TDP is

enabled by default.

• Cisco IOS Releases 12.4 and 12.4T and later releases:

LDP is enabled by default.

• Cisco IOS Release 12.3(11)T and earlier releases: TDP is

supported for LDP features.

• Cisco IOS Release 12.3(14)T and later releases: TDP is

not support ed for LDP features.

Directly Connected MPLS LDP Sessions

If an LSR is one hop from its neighbor, it is directly connected to its neighbor. The LSR sends out LDP link Hello messages as User Datagram Protocol (UDP) packets to all the routers on the subnet (multicast). A neighboring LSR may respond to the link Hello message, allowing the two routers to establish an LDP session. This is called basic discovery.

To initiate an LDP session between routers, the routers determine which router will take the active role and which router will take the passive role. The router that takes the active role establishes the LDP TCP connection session and initiates the negotiation of the LDP session parameters. To determine the roles, the two routers compare their transport addresses. The router with the higher IP address takes the active role and establishes the session.

After the LDP TCP connection session is established, the LSRs negotiate the session parameters, including the method of label distribution to be used. Two methods are available:

• Downstream Unsolicited: An LSR advertises label mappings to peers without being asked to.

• Downstream on Demand: An LSR advertises label mappings to a peer only when the peer asks for them.

For information about creating LDP sessions, see the Enabling Directly Connected LDP Sessions, page

6.

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Nondirectly Connected MPLS LDP Sessions

If the LSR is more than one hop from its neighbor, it is nondirectly connected to its neighbor. For these nondirectly connected neighbors, the LSR sends out a targeted Hello message as a UDP packet, but as a unicast message specifically addressed to that LSR. The nondirectly connected LSR responds to the Hello message and the two routers begin to establish an LDP session. This is called extended discovery.

An MPLS LDP targeted session is a label distribution session between routers that are not directly connected. When you create an MPLS traffic engineering tunnel interface, you need to establish a label distribution session between the tunnel headend and the tailend routers. You establish nondirectly connected MPLS LDP sessions by enabling the transmission of targeted Hello messages.

You can use the mpls ldp neighbor targetedcommand to set up a targeted session when other means of establishing targeted sessions do not apply, such as configuring mpls ipon a traffic engineering (TE) tunnel or configuring Any Transport over MPLS (AToM) virtual circuits (VCs). For example, you can use this command to create a targeted session between directly connected MPLS label switch routers (LSRs) when MPLS label forwarding convergence time is an issue.

The mpls ldp neighbor targetedcommand can improve label convergence time for directly connected neighbor LSRs when the link(s) directly connecting them are down. When the links between the neighbor LSRs are up, both the link and targeted Hellos maintain the LDP session. If the links between the neighbor LSRs go down, the targeted Hellos maintain the session, allowing the LSRs to retain labels learned from each other. When a link directly connecting the LSRs comes back up, the LSRs can immediately reinstall labels for forwarding use without having to reestablish their LDP session and exchange labels.

The exchange of targeted Hello messages between two nondirectly connected neighbors can occur in several ways, including the following:

Introduction to LDP Label Bindings Label Spaces and LDP Identifiers

• Router 1 sends targeted Hello messages carrying a response request to Router 2. Router 2 sends targeted Hello messages in response if its configuration permits. In this situation, Router 1 is considered to be active and Router 2 is considered to be passive.

• Router 1 and Router 2 both send targeted Hello messages to each other. Both routers are considered to be active. Both, one, or neither router can also be passive, if 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 that send targeted Hello messages. You can configure an LSR to respond to requests for targeted Hello messages by issuing the mpls ldp discovery targeted-hello accept command.

The active LSR mandates the protocol that is used for a targeted session. The passive LSR uses the protocol of the received targeted Hello messages.

For information about creating MPLS LDP targeted sessions, see the Establishing Nondirectly Connected

MPLS LDP Sessions, page 8.

Introduction to LDP 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, label-controlled ATM (LC-ATM) interfaces use virtual path identifiers/virtual circuit identifiers (VPIs/ VCIs) for labels. Depending on its configuration, an LDP platform may support zero, one, or more interface-specific label spaces.

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MPLS Label Distribution Protocol (LDP)

• 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 platformwide label space.

LDP uses a 6-byte quantity called an LDP Identifier (or LDP ID) to name label spaces. The LDP ID is made up of the following components:

• The first four bytes, called the LPD router ID, identify the LSR that owns the label space.

• The last two bytes, called the local label space ID, 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 LDP ID takes the following form: <LDP router ID> : <local label space ID> The following are examples of LPD IDs:

• 172.16.0.0:0

• 192.168.0.0:3

The router determines the LDP router ID as follows, if the mpls ldp router-id command is not executed,

How to Configure MPLS LDP

The router examines the IP addresses of all operational interfaces.

1

If these IP addresses include loopback interface addresses, the router selects the largest loopback

2

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

3

router ID.

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, the router might select an IP address as the LDP router ID that the routing protocol cannot advertise to a neighboring router. The mpls ldp router-id command allows you to specify the IP address of an interface as the LDP router ID. Make sure the specified interface is operational so that its IP address can be used as the LDP router ID.

When you issue the mpls ldp router-id command without the force keyword, the router select selects 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, which is typically the next time the interface is shut down or the address is configured.

When you issue the mpls ldp router-idcommand with the force keyword, the effect of the mpls ldp router-idcommand depends on the current state of the specified interface:

• If the interface is up (operational) and if its IP address is not currently the LDP router ID, the LDP

router ID changes 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.

•

If the interface is down (not operational) when the mpls ldp router-idinterface force command is issued, when the interface transitions to up, the LDP router ID changes 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.

How to Configure MPLS LDP

• Enabling Directly Connected LDP Sessions, page 6

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How to Configure MPLS LDP

• Establishing Nondirectly Connected MPLS LDP Sessions, page 8

• Saving Configurations MPLS Tag Switching Commands, page 11

• Specifying the LDP Router ID, page 12

• Preserving QoS Settings with MPLS LDP Explicit Null, page 14

• Protecting Data Between LDP Peers with MD5 Authentication, page 18

Enabling Directly Connected LDP Sessions

This procedure explains how to configure MPLS LDP sessions between two directly connected routers.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol {ldp | tdp | both}

5.

Router(config)# interface type number

6.

mpls ip

7.

exit

8.

exit

9.

show mpls interfaces [interface] [detail

10.

show mpls ldp discovery [all | vrf vpn-name] [detail

11.

show mpls ldp neighbor [[vrf vpn-name] [address | interface] [detail] | [all]]

Enabling Directly Connected LDP Sessions

DETAILED STEPS

Command or Action

Step 1

Step 2

Step 3

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Router(config)# mpls ip

Purpose

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Configures MPLS hop-by-hop forwarding globally.

•

The mpls ip command is enabled by default; you do not have to specify this command.

• Globally enabling MPLS forwarding does not enable it on the router interfaces. You must enable MPLS forwarding on the interfaces as well as for the router.

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MPLS Label Distribution Protocol (LDP)

Command or Action Purpose

How to Configure MPLS LDP

Step 4

Step 5

Step 6

Step 7

mpls label protocol {ldp | tdp | both}

Example:

Router(config)# mpls label protocol ldp

Router(config)# interface type number

Example:

Router(config)# interface ethernet3/0

mpls ip

Example:

Router(config-if)# mpls ip

exit

Example:

Router(config-if)# exit

Configures the use of LDP on all interfaces. LDP is the default.

• If you set all interfaces globally to LDP, you can override

specific interfaces with either the tdp or both keyword by specifying the command in interface configuration mode.

Specifies the interface to be configured and enters interface configuration mode.

Configures MPLS hop-by-hop forwarding on the interface.

• You must enable MPLS forwarding on the interfaces as well

as for the router.

Exits interface configuration mode and enters global configuration mode.

Step 8

Step 9

Step 10

exit

Example:

Router(config)# exit

show mpls interfaces [interface] [detail

Example:

Router# show mpls interfaces

show mpls ldp discovery [all | vrf vpn-name] [detail

Example:

Router# show mpls ldp discovery

Exits global configuration mode and enters privileged EXEC mode.

Verifies that the interfaces have been configured to use LDP, TDP, or both.

Verifies that the interface is up and is sending Discovery Hello messages.

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How to Configure MPLS LDP

Command or Action Purpose

Establishing Nondirectly Connected MPLS LDP Sessions

Step 11

show mpls ldp neighbor [[vrf vpn-name] [address | interface] [detail] | [all]]

Example:

Router# show mpls ldp neighbor

Examples

The following show mpls interfaces command verifies that interfaces Ethernet 1/0 and 1/1 have been configured to use LDP:

Router# show mpls interfaces Interface IP Tunnel BGP Static Operational Ethernet3/0 Yes (ldp) No No No Yes Ethernet3/1 Yes No No No Yes

The following show mpls ldp discovery command verifies that the interface is up and is sending LDP Discovery Hello messages (as opposed to TDP Hello messages):

Router# show mpls ldp discovery Local LDP Identifier:

172.16.12.1:0 Discovery Sources: Interfaces: Ethernet3/0 (ldp): xmit

The following example shows that the LDP session between routers was successfully established:

Displays the status of LDP sessions.

Router# show mpls ldp neighbor Peer LDP Ident: 10.1.1.2:0; Local LDP Ident 10.1.1.1:0 TCP connection: 10.1.1.2.18 - 10.1.1.1.66 State: Oper; Msgs sent/rcvd: 12/11; Downstream Up time: 00:00:10 LDP discovery sources: FastEthernet1/0, Src IP addr: 10.20.10.2 Addresses bound to peer LDP Ident:

10.1.1.2 10.20.20.1 10.20.10.2

For examples on configuring directly connected LDP sessions, see the Configuring Directly Connected

MPLS LDP Sessions Example, page 21.

Establishing Nondirectly Connected MPLS LDP Sessions

This section explains how to configure nondirectly connected MPLS LDP sessions, which enable you to establish an LDP session between routers that are not directly connected.

• MPLS requires CEF.

• You must configure the routers at both ends of the tunnel to be active or enable one router to be

passive with the mpls ldp discovery targeted-hello accept command.

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MPLS Label Distribution Protocol (LDP)

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol {ldp | tdp | both}

5.

interface tunnelnumber

6.

tunnel destination ip-address

7.

mpls ip

8.

exit

9.

exit

10.

show mpls ldp discovery [all | vrf vpn-name] [detail

DETAILED STEPS

Command or Action Purpose

How to Configure MPLS LDP

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Router(config)# mpls ip

mpls label protocol {ldp | tdp | both}

Example:

Router(config)# mpls label protocol ldp

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Configures MPLS hop-by-hop forwarding globally.

•

The mpls ip command is enabled by default; you do not have to specify this command.

• Globally enabling MPLS forwarding does not enable it on the router interfaces. You must enable MPLS forwarding on the interfaces as well as for the router.

Configures the use of LDP on all interfaces. LDP is the default.

• If you set all interfaces globally to LDP, you can override specific interfaces with either the tdp or both keyword by specifying the command in interface configuration mode.

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How to Configure MPLS LDP

Command or Action Purpose

MPLS Label Distribution Protocol (LDP)

Step 5

Step 6

Step 7

Step 8

interface tunnelnumber

Example:

Router(config)# interface tunnel1

tunnel destination ip-address

Example:

Router(config-if)# tunnel destination

172.16.1.1

mpls ip

Example:

Router(config-if)# mpls ip

exit

Example:

Configures a tunnel interface and enters interface configuration mode.

Assigns an IP address to the tunnel interface.

Configures MPLS hop-by-hop forwarding on the interface.

• You must enable MPLS forwarding on the interfaces as well as for the router.

Exits interface configuration mode and enters global configuration mode.

Step 9

Step 10

Router(config-if)# exit

exit

Example:

Router(config)# exit

show mpls ldp discovery [all | vrf vpn-name] [detail

Example:

Router# show mpls ldp discovery

Example

The following example shows the output of the show mpls ldp discovery command for a nondirectly connected LDP session.

Router# show mpls ldp discovery Local LDP Identifier:

172.16.0.0:0 Discovery Sources:

Exits global configuration mode and enters privileged EXEC mode.

Verifies that the interface is up and is sending Discovery Hello messages.

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MPLS LDP Configuration Guide, Cisco IOS Release 12.4

Saving Configurations MPLS Tag Switching Commands

Interfaces: POS2/0 (ldp): xmit/recv LDP Id: 172.31.255.255:0 Tunnel1 (ldp): Targeted -> 192.168.255.255 Targeted Hellos:

172.16.0.0 -> 192.168.255.255 (ldp): active, xmit/recv LDP Id: 192.168.255.255:0

172.16.0.0 -> 192.168.0.0 (tdp): passive, xmit/recv TDP Id: 192.168.0.0:0

This command output indicates that:

• The local LSR (172.16.0.0) sent LDP link Hello messages on interface POS2/0 and discovered neighbor 172.31.255.255.

• The local LSR sent LDP targeted Hello messages associated with interface Tunnel1 to target

192.168.255.255. The LSR was configured to use LDP.

• The local LSR is active for targeted discovery activity with 192.168.255.255; this means that the targeted Hello messages it sends to 192.168.255.255 carry a response request. The local LSR was configured to have an LDP session with the nondirectly connected LSR 192.168.255.255.

• The local LSR is not passive from the discovery activity with 192.168.255.255 for one of the following reasons:

◦ The targeted Hello messages it receives from 192.168.255.255 do not carry a response request. ◦ The local LSR has not been configured to respond to such requests.

• The local LSR sent TDP directed Hello messages to the target LSR 192.168.0.0. This LSR uses TDP because the Hello messages received from the target LSR 192.168.0.0 were TDP directed Hello messages.

• The local LSR is passive in discovery activity with LSR 192.168.0.0. This means that the directed Hello messages it receives from LSR 192.168.0.0 carry a response request and that the local LSR has been configured with the mpls ldp discovery targeted-hello accept command to respond to such requests from LSR 192.168.0.0.

• The local LSR is not active in discovery activity with LSR 192.168.0.0, because no application that requires an LDP session with LSR 192.168.0.0 has been configured on the local LSR.

How to Configure MPLS LDP

For examples of configuring LDP targeted sessions, see the Establishing Nondirectly Connected MPLS

LDP Sessions Example, page 23.

Saving Configurations MPLS Tag Switching Commands

In releases of Cisco IOS software prior to 12.4(2)T, some MPLS commands had both a tag-switching version and an MPLS version. For example, the two commands tag-switching ip and mpls ip were the same. To support backward compatibility, the tag-switching form of the command was written to the saved configuration.

Starting in Cisco IOS Release 12.4(2)T, the MPLS form of the command is written to the saved configuration.

For example, if an ATM interface is configured using the following commands, which have both a tagswitching form and an MPLS form:

Router(config)# interface ATM3/0 Router(config-if)# ip unnumbered Loopback0 router(config-if)# tag-switching ip Router(config-if)# mpls label protocol ldp

After you enter these commands and save this configuration or display the running configuration with the show runningcommand, the commands saved or displayed appear as follows:

interface ATM3/0

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How to Configure MPLS LDP

ip unnumbered Loopback0 mpls ip mpls label protocol ldp

Specifying the LDP Router ID

The mpls ldp router-id command allows you to establish the IP address of an interface as the LDP router ID.

The following steps describe the normal process for determining the LDP router ID:

The router considers all the IP addresses of all operational interfaces.

1

If these addresses include loopback interface addresses, the router selects the largest loopback address.

2

Configuring a loopback address helps ensure a stable LDP ID for the router, because the state of loopback addresses does not change. However, configuring a loopback interface and IP address on each router is not required.

The loopback IP address does not become the router ID of the local LDP ID under the following circumstances:

• ◦ If the loopback interface has been explicitly shut down.

◦

If the mpls ldp router-id command specifies that a different interface should be used as the LDP router ID.

Specifying the LDP Router ID

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.

Otherwise, the router selects the largest interface address.

1

The router might select a router ID that is not usable in certain situations. For example, the router might select an IP address that the routing protocol cannot advertise to a neighboring router.

The router implements the router ID 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 is shut down or the address is deconfigured.

If you use the force keyword with the mpls ldp router-id command, the router ID takes effect more quickly. However, implementing the router ID depends on the current state of the specified interface:

• If the interface is up (operational) and 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.

• If the interface is down, the LDP router ID is forcibly changed to the IP address of the interface when the interface transitions to up. 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.

Make sure the specified interface is operational before assigning it as the LDP router ID.

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SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol {ldp | tdp | both}

5.

mpls ldp router-id interface [force]

6.

exit

7.

show mpls ldp discovery [all | detail |vrf vpn-name]

DETAILED STEPS

Command or Action Purpose

How to Configure MPLS LDP

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Router(config)# mpls ip

mpls label protocol {ldp | tdp | both}

Example:

Router(config)# mpls label protocol ldp

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Configures MPLS hop-by-hop forwarding globally.

•

The mpls ip command is enabled by default; you do not have to specify this command.

• Globally enabling MPLS forwarding does not enable it on the router interfaces. You must enable MPLS forwarding on the interfaces as well as for the router.

Configures the use of LDP on all interfaces. LDP is the default.

• If you set all interfaces globally to LDP, you can override specific interfaces with either the tdp or both keyword by specifying the command in interface configuration mode.

Step 5

mpls ldp router-id interface [force]

Example:

Router(config)# mpls ldp

Specifies the preferred interface for determining the LDP router ID.

router-id pos2/0/0

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Command or Action Purpose

Preserving QoS Settings with MPLS LDP Explicit Null

Step 6

Step 7

exit

Example:

Router(config)# exit

show mpls ldp discovery [all | detail |vrf vpnname]

Example:

Router# show mpls ldp discovery

Example

The following example assigns interface pos2/0/0 as the LDP router ID:

Router> enable Router# configure terminal Router(config)# mpls ip Router(config)# mpls label protocol ldp

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

The following example displays the LDP router ID (10.15.15.15):

Exits global configuration mode and enters privileged EXEC mode.

Displays the LDP identifier for the local router.

Router# show mpls ldp discovery Local LDP Identifier:

10.15.15.15:0 Discovery Sources: Interfaces: Ethernet4 (ldp): xmit/recv LDP Id: 10.14.14.14:0

Preserving QoS Settings with MPLS LDP Explicit Null

Normally, LDP advertises an Implicit Null label for directly connected routes. The Implicit Null label causes the second last (penultimate) label switched router (LSR) to remove the MPLS header from the packet. In this case, the penultimate LSR and the last LSR do not have access to the quality of service (QoS) values that the packet carried before the MPLS header was removed. To preserve the QoS values, you can configure the LSR to advertise an explicit NULL label (a label value of zero). The LSR at the penultimate hop forwards MPLS packets with a NULL label instead of forwarding IP packets.

Note

An explicit NULL label is not needed when the penultimate hop receives MPLS packets with a label stack that contains at least two labels and penultimate hop popping is performed. In that case, the inner label can still carry the QoS value needed by the penultimate and edge LSR to implement their QoS policy.

When you issue the mpls ldp explicit-null command, Explicit Null is advertised in place of Implicit Null for directly connected prefixes.

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SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol {ldp | tdp | both}

5.

interface type number

6.

mpls ip

7.

exit

8.

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

9.

exit

10.

show mpls forwarding-table [network {mask | length} | labels label [- label] | interface interface | next-hop address | lsp-tunnel[tunnel-id]] [vrf vpn-name] [detail]

DETAILED STEPS

How to Configure MPLS LDP

Step 1

Step 2

Step 3

Step 4

Command or Action Purpose

enable

Enables privileged EXEC mode.

• Enter your password if prompted.

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Enters global configuration mode.

Configures MPLS hop-by-hop forwarding globally.

•

The mpls ip command is enabled by default; you do not have to specify this command.

• Globally enabling MPLS forwarding does not enable it on

Router(config)# mpls ip

the router interfaces. You must enable MPLS forwarding on the interfaces as well as for the router.

mpls label protocol {ldp | tdp | both}

Configures the use of LDP on all interfaces. LDP is the default.

• If you set all interfaces globally to LDP, you can override

Example:

Router(config)# mpls label protocol ldp

specific interfaces with either the tdp or both keyword by specifying the command in interface configuration mode.

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How to Configure MPLS LDP

Command or Action Purpose

MPLS Label Distribution Protocol (LDP)

Step 5

Step 6

Step 7

Step 8

interface type number

Example:

Router(config)# interface atm2/0

mpls ip

Example:

Router(config-if)# mpls ip

exit

Example:

Router(config-if)# exit

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

Specifies the interface to be configured and enters interface configuration mode.

Configures MPLS hop-by-hop forwarding on the interface.

• You must enable MPLS forwarding on the interfaces as well as for the router.

Exits interface configuration mode and enters global configuration mode.

Advertises an Explicit Null label in situations where it would normally advertise an Implicit Null label.

Step 9

Step 10

Example:

Router(config)# mpls ldp explicit-null

exit

Example:

Router(config)# exit

show mpls forwarding-table [network {mask | length} | labels label [- label] | interface interface | next-hop address | lsp-tunnel[tunnel-id]] [vrf vpnname] [detail]

Example:

Router# show mpls forwarding-table

Exits global configuration mode and enter privileged EXEC mode.

Verifies that MPLS packets are forwarded with an explicit-null label (value of 0).

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Examples

Enabling explicit-null on an egress LSR causes that LSR to advertise the explicit-null label to all adjacent MPLS routers.

Router# configure terminal Router(config)# mpls ldp explicit-null

If you issue the show mpls forwarding-table command on an adjacent router, the output shows that MPLS packets are forwarded with an explicit-null label (value of 0). In the following example, the second column shows that entries have outgoing labels of 0, where once they were marked “Pop label”.

Router# show mpls forwarding-table Local Outgoing Prefix Bytes label Outgoing Next Hop label label or VC or Tunnel Id switched interface 19 Pop tag 10.12.12.12/32 0 Fa2/1/0 172.16.0.1 22 0 10.14.14.14/32 0 Fa2/0/0 192.168.0.2 23 0 172.24.24.24/32 0 Fa2/0/0 192.168.0.2 24 0 192.168.0.0/8 0 Fa2/0/0 192.168.0.2 25 0 10.15.15.15/32 0 Fa2/0/0 192.168.0.2 26 0 172.16.0.0/8 0 Fa2/0/0 192.168.0.2 27 25 10.16.16.16/32 0 Fa2/0/0 192.168.0.22 28 0 10.34.34.34/32 0 Fa2/0/0 192.168.0.2

Enabling explicit-null and specifying the forkeyword with a standard access control list (ACL) changes all adjacent MPLS routers' tables to swap an explicit-null label for only those entries specified in the accesslist. In the following example, an access-list is created that contains the 10.24.24.24/32 entry. Explicit null is configured and the access list is specified.

How to Configure MPLS LDP

Router# configure terminal Router(config)# mpls label protocol ldp Router(config)# access-list 24 permit host 10.24.24.24 Router(config)# mpls ldp explicit-null for 24

If you issue the show mpls forwarding-table command on an adjacent router, the output shows that the only the outgoing labels for the addresses specified (172.24.24.24/32) change from Pop label to 0. All other Pop label outgoing labels remain the same.

Router# show mpls forwarding-table Local Outgoing Prefix Bytes label Outgoing Next Hop label label or VC or Tunnel Id switched interface 19 Pop tag 10.12.12.12/32 0 Fa2/1/0 172.16.0.1 22 0 10.14.14.14/32 0 Fa2/0/0 192.168.0.2 23 0 172.24.24.24/32 0 Fa2/0/0 192.168.0.2 24 0 192.168.0.0/8 0 Fa2/0/0 192.168.0.2 25 0 10.15.15.15/32 0 Fa2/0/0 192.168.0.2 26 0 172.16.0.0/8 0 Fa2/0/0 192.168.0.2 27 25 10.16.16.16/32 0 Fa2/0/0 192.168.0.22 28 0 10.34.34.34/32 0 Fa2/0/0 192.168.0.2

Enabling explicit null and adding the to keyword and an access list enables you to advertise explicit-null labels to only those adjacent routers specified in the access-list.To advertise explicit-null to a particular router, you must specify the router's LDP ID in the access-list.

In the following example, an access-list contains the 10.15.15.15/32 entry, which is the LDP ID of an adjacent MPLS router. The router that is configured with explicit null advertises explicit-null labels only to that adjacent router.

Router# show mpls ldp discovery Local LDP Identifier:

10.15.15.15:0 Discovery Sources: Interfaces: Ethernet4 (ldp): xmit/recv TDP Id: 10.14.14.14:0

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How to Configure MPLS LDP

Router# configure terminal Router(config)# mpls label protocol ldp Router(config)# access-list 15 permit host 10.15.15.15 Router(config)# mpls ldp explicit-null to 15

If you issue the show mpls forwarding-table command, the output shows that explicit null labels are going only to the router specified in the access list.

Router# show mpls forwarding-table Local Outgoing Prefix Bytes label Outgoing Next Hop label label or VC or Tunnel Id switched interface 19 Pop tag 10.12.12.12/32 0 Fa2/1/0 172.16.0.1 22 0 10.14.14.14/32 0 Fa2/0/0 192.168.0.2 23 0 172.24.24.24/32 0 Fa2/0/0 192.168.0.2 24 0 192.168.0.0/8 0 Fa2/0/0 192.168.0.2 25 0 10.15.15.15/32 0 Fa2/0/0 192.168.0.2 26 0 172.16.0.0/8 0 Fa2/0/0 192.168.0.2 27 25 10.16.16.16/32 0 Fa2/0/0 192.168.0.22 28 0 10.34.34.34/32 0 Fa2/0/0 192.168.0.2

Enabling explicit-null with both the forand tokeywords enables you to specify which routes to advertise with explicit-null labels and to which adjacent routers to advertise these explicit-null labels.

Router# show access 15 Standard IP access list 15 permit 10.15.15.15 (7 matches) Router# show access 24 Standard IP access list 24 permit 10.24.24.24 (11 matches) Router# configure terminal Router(config)# mpls label protocol ldp Router(config)# mpls ldp explicit-null for 24 to 15

If you issue the show mpls forwarding-table command on the router called 47K-60-4, the output shows that it receives explicit null labels for 10.24.24.24/32.

Protecting Data Between LDP Peers with MD5 Authentication

Router# show mpls forwarding-table Local Outgoing Prefix Bytes label Outgoing Next Hop label label or VC or Tunnel Id switched interface 17 0 <--- 10.24.24.24/32 0 Et4 172.16.0.1 20 Pop tag 172.16.0.0/8 0 Et4 172.16.0.1 21 20 10.12.12.12/32 0 Et4 172.16.0.1 22 16 10.0.0.0/8 0 Et4 172.16.0.1 23 21 10.13.13.13/32 0 Et4 172.16.0.1 25 Pop tag 10.14.14.14/32 0 Et4 172.16.0.1 27 Pop tag 192.168.0.0/8 0 Et4 172.16.0.1 28 25 10.16.16.16/32 0 Et4 172.16.0.1 29 Pop tag 192.168.34.34/32 0 Et4 172.16.0.1

Protecting Data Between LDP Peers with MD5 Authentication

You can enable authentication between two LDP peers, which verifies each segment sent on the TCP connection between the peers. You must configure authentication on both LDP peers using the same password; otherwise, the peer session is not established.

Authentication uses the Message Digest 5 (MD5) algorithm to verify the integrity of the communication and authenticate the origin of the message.

To enable authentication, issue the mpls ldp neighborcommand with the passwordkeyword. This causes the router to generate an MD5 digest for every segment sent on the TCP connection and check the MD5 digest for every segment received from the TCP connection.

When you configure a password for an LDP neighbor, the router tears down existing LDP sessions and establishes new sessions with the neighbor.

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

%TCP-6-BADAUTH: No MD5 digest from [peer's IP address](11003) to [local router's IP address](646) Similarly, if the two routers have different passwords configured, a message such as the following appears

on the console. The LDP session is not established. %TCP-6-BADAUTH: Invalid MD5 digest from [peer's IP address](11004) to [local router's IP address]

(646)

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol {ldp | tdp | both}

5.

mpls ldp neighbor [vrf vpn-name] ip-address[password[0-7] password-string]

6.

exit

7.

show mpls ldp neighbor [[vrf vpn-name] [address | interface] [detail] | [all]]

How to Configure MPLS LDP

DETAILED STEPS

Command or Action Purpose

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Router(config)# mpls ip

mpls label protocol {ldp | tdp | both}

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Configures MPLS hop-by-hop forwarding globally.

•

The mpls ip command is enabled by default; you do not have to specify this command.

• Globally enabling MPLS forwarding does not enable it on the router interfaces. You must enable MPLS forwarding on the interfaces as well as for the router.

Configures the use of LDP on all interfaces. LDP is the default.

• If you set all interfaces globally to LDP, you can override

Example:

Router(config)# mpls label protocol ldp

19

specific interfaces with either the tdp or both keyword by specifying the command in interface configuration mode.

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How to Configure MPLS LDP

Command or Action Purpose

MPLS Label Distribution Protocol (LDP)

Step 5

Step 6

Step 7

mpls ldp neighbor [vrf vpn-name] ipaddress[password[0-7] password-string]

Example:

Router(config)# mpls ldp

neighbor 172.27.0.15 password onethirty9

exit

Example:

Router(config)# exit

show mpls ldp neighbor [[vrf vpn-name] [address | interface] [detail] | [all]]

Example:

Router# show mpls ldp neighbor detail

Specifies authentication between two LDP peers.

Exits global configuration mode and enters privileged EXEC mode.

Displays the status of LDP sessions. If the passwords have been set on both LDP peers and the

passwords match, the show mpls ldp neighbor command displays that the LDP session was successfully established.

Examples

The following example configures a router with the password cisco:

Router> enable

Router# configure terminal

Router(config)# mpls ip Router(config)# mpls label protocol ldp Router(config)# mpls ldp neighbor 10.1.1.1 password cisco Router(config)# exit

The following example shows that the LDP session between routers was successfully established:

Router# show mpls ldp neighbor Peer LDP Ident: 10.1.1.2:0; Local LDP Ident 10.1.1.1:0 TCP connection: 10.1.1.2.11118 - 10.1.1.1.646 State: Oper; Msgs sent/rcvd: 12/11; Downstream Up time: 00:00:10 LDP discovery sources: FastEthernet1/0, Src IP addr: 10.20.10.2 Addresses bound to peer LDP Ident:

10.1.1.2 10.20.20.1 10.20.10.2

The following show mpls ldp neighbor detail command shows that MD5 (shown in bold) is used for the LDP session.

Router# show mpls ldp neighbor 10.0.0.21 detail

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Configuring Directly Connected MPLS LDP Sessions Example

MPLS LDP Configuration Examples

Peer LDP Ident: 10.0.0.21:0; Local LDP Ident 10.0.0.22:0 TCP connection: 10.0.0.21.646 - 10.0.0.22.14709; MD5 on State: Oper; Msgs sent/rcvd: 1020/1019; Downstream; Last TIB rev sent 2034 Up time: 00:00:39; UID: 3; Peer Id 1; LDP discovery sources: FastEthernet1/1; Src IP addr: 172.16.1.1 holdtime: 15000 ms, hello interval: 5000 ms Addresses bound to peer LDP Ident:

10.0.0.21 10.0.38.28 10.88.88.2 172.16.0.1

172.16.1.1 Peer holdtime: 180000 ms; KA interval: 60000 ms; Peer state: estab

MPLS LDP Configuration Examples

• Configuring Directly Connected MPLS LDP Sessions Example, page 21

• Establishing Nondirectly Connected MPLS LDP Sessions Example, page 23

Configuring Directly Connected MPLS LDP Sessions Example

The figure below shows a sample network for configuring directly connected LDP sessions. This example configures the following:

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

• LDP for label distribution between Router 1 and Router 2.

• TDP for label distribution between Router 1 and Router 3.

• A loopback interface and IP address for each LSR that can be used as the LDP router ID.

Figure 1

Configuration of MPLS LDP

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MPLS LDP Configuration Examples

MPLS Label Distribution Protocol (LDP)

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 the figure above.

Router 1 Configuration

ip cef distributed !Assumes R1 supports distributed CEF interface Loopback0 !Loopback interface for LDP ID. ip address 172.16.0.11 255.255.255.255 ! interface POS3/0/0 ip address 10.0.0.44 255.0.0.0 mpls ip !Enable hop-by-hop MPLS forwarding mpls label protocol ldp !Use LDP for this interface ! interface POS3/0/1 ip address 192.168.0.44 255.0.0.0 mpls ip !Enable hop-by-hop MPLS forwarding mpls label protocol tdp !Use TDP for this interface

Router 2 Configuration

ip cef distributed !Assumes R2 supports distributed CEF ! interface Loopback0 !Loopback interface for LDP ID. ip address 172.16.0.22 255.255.255.255 ! interface POS2/0/0 ip address 10.0.0.33 255.0.0.0 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 dCEF ! interface Loopback0 !Loopback interface for LDP ID. ip address 172.16.0.33 255.255.255.255 ! interface POS1/0 ip address 192.168.0.55 255.0.0.0 mpls ip !Enable hop-by-hop MPLS forwarding mpls label protocol tdp !Use tDP for this interface

The LDP configuration for Router 1 uses the mpls label protocol ldpcommand in interface configuration mode, because some of its interfaces use LDP and some use TDP. Another way to configure Router 1 is to use the mpls label protocol ldpcommand in global configuration mode to configure LDP as the default protocol for interfaces and use the mpls label protocol tdpcommand in interface configuration mode 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 dCEF mpls label protocol ldp !Use LDP for the default protocol ! interface Loopback0 !Loopback interface for LDP ID. ip address 172.16.0.11 255.255.255.255 interface POS3/0/0 ip address 10.0.0.44 255.0.0.0 mpls ip !Enable hop-by-hop MPLS forwarding

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MPLS LDP Configuration Examples

!Use LDP (configured i/f default) interface POS3/0/1 ip address 192.168.0.44 255.0.0.0 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 mpls label protocol ldpcommand in interface configuration mode. To specify LDP for all interfaces, use the mpls label protocol ldpcommand in global configuration mode without any interface mpls label protocol commands.

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

Establishing Nondirectly Connected MPLS LDP Sessions Example

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

Figure 2 Sample Network for Configuring LDP for Targeted Sessions

The configuration example shows the following:

• Targeted sessions between Routers 1 and 4 use LDP. Routers 1 and 4 are both active.

• Targeted sessions between Routers 1 and 6 use LDP. Router 1 is active and Router 6 is passive.

• Targeted sessions between Routers 1 and 5 use TDP. Router 5 is active.

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

Router 1 Configuration

Tunnel interfaces Tunnel14 and Tunnel16 specify LDP for targeted sessions associated with these interfaces. The targeted session for Router 5 requires TDP. The mpls label protocol ldp command in

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MPLS LDP Configuration Examples

global configuration mode makes it unnecessary to explicitly specify LDP as part of the configuration from the Tunnel14 and Tunnel16.

ip cef distributed !Router1 supports distributed CEF mpls label protocol ldp !Use LDP as default for all interfaces interface Loopback0 !Loopback interface for LDP ID. ip address 10.25.0.11 255.255.255.255 interface Tunnel14 !Tunnel to Router 4 requiring label distribution tunnel destination 10.11.0.4 !Tunnel endpoint is Router 4 mpls ip !Enable hop-by-hop forwarding on the interface interface Tunnel15 !Tunnel to Router 5 requiring label distribution tunnel destination 10.11.0.5 !Tunnel endpoint is Router 5 mpls label protocol tdp !Use TDP for session with Router 5 mpls ip !Enable hop-by-hop forwarding on the interface interface Tunnel16 !Tunnel to Router 6 requiring label distribution tunnel destination 10.11.0.6 !Tunnel endpoint is Router 6 mpls ip !Enable hop-by-hop forwarding on the interface

Router 4 Configuration

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

MPLS Label Distribution Protocol (LDP)

ip cef distributed !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 10.25.0.44 255.255.255.255 interface Tunnel41 !Tunnel to Router 1 requiring label distribution tunnel destination 10.11.0.1 !Tunnel endpoint is Router 1 mpls ip !Enable hop-by-hop forwarding on the interface

Router 5 Configuration

Router 5 must use TDP for all targeted sessions. Therefore, its configuration includes the mpls label protocol tdpcommand.

ip cef !Router 5 supports CEF mpls label protocol tdp !Use TDP as default for all interfaces interface Loopback0 !Loopback interface for LDP ID. ip address 10.25.0.55 255.255.255.255 interface Tunnel51 !Tunnel to Router 1 requiring label distribution tunnel destination 10.11.0.1 !Tunnel endpoint is Router 1 mpls ip !Enable hop-by-hop forwarding on the interface

Router 6 Configuration

By default, a router cannot be a passive neighbor in targeted sessions. Therefore, Router 1, Router 4, and Router 5 are active neighbors in any targeted sessions. 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.

ip cef distributed !Router 6 supports distributed CEF interface Loopback0 !Loopback interface for LDP ID. ip address 10.25.0.66 255.255.255.255 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 10.11.0.1 !Accept targeted hello request from Router 1. deny any !Deny requests from other sources.

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Additional References

Related Documents

Feature Information for MPLS Label Distribution Protocol

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

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MPLS Label Distribution Protocol (LDP)

Table 2 Feature Information for MPLS Label Distribution Protocol Overview

Feature Name Releases Feature Information

Feature Information for MPLS Label Distribution Protocol

MPLS Label Distribution Protocol

12.0(10)ST 12.0(14)ST 12.1(2)T

12.1(8a)E 12.2(2)T 12.2(4)T

12.2(8)T 12.0(21)ST 12.0(22)S

12.0(23)S 12.2(13)T 12.4(3)

12.4(5)

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 MPLS 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).

In Cisco IOS Release 12.0(14)ST, several new MPLS CLI commands were introduced, support for MPLS VPNs was added by means of a new vrf vpn- nameparameter in certain existing commands, and other commands were modified to ensure consistent interpretation of associated prefix-access-list arguments by Cisco IOS software.

In Cisco IOS 12.1(2)T, this feature was integrated into this release. Also, the debug mpls

atm-ldp api, debug mpls atmldp routes,and debug mpls atmldp statescommandswere

modified. This feature was integrated into

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

Cisco IOS Release 12.2(2)T. The following commands were

introduced or modified by this feature: mpls label protocol (global configuration), mpls ldp

router-id.

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

27

Feature Information for MPLS Label Distribution Protocol

Feature Name Releases Feature Information

MPLS Label Distribution Protocol (LDP)

In Cisco IOS Release 12.2(4)T, 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. In Cisco IOS Release 12.2(8)T,

the debug mpls atm-ldp failurecommand was introduced.

In Cisco IOS Release 12.0(21)ST, the mpls ldp neighbor implicit- withdrawcommand was introduced.

This feature was integrated into Cisco IOS Release 12.0(22)S. The mpls ldp neighbor targeted-sessioncommand and the interface keyword for the

mpls ldp advertiselabelscommand were added.

This feature was integrated into Cisco IOS Release 12.0(23)S. Default values for the mpls ldp discoverycommand holdtime and interval keywords were changed.

This feature was integrated into Cisco IOS Release 12.2(13)T.

In Cisco IOS Release 12.4(3), the default MPLS label distribution protocol changed from TDP to LDP. See LDP and TDP

Support, page 2 for more

information. If no protocol is explicitly configured by the mpls label protocol command, LDP is the default label distribution protocol. See the mpls label protocol (global configuration) command for more information.

Also in Cisco IOS Release

12.4(3), LDP configuration commands are saved by using the MPLS form of the command

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Feature Name Releases Feature Information

rather than the tag-switching form. Previously, commands were saved by using the tagswitching form of the command, for backward compatibility. See the Saving Configurations MPLS

Tag Switching Commands, page 11 for more information.

In Cisco IOS Release 12.4(5), the vrf vrf-name keyword/argument pair was added for the mpls ldp router-id command to allow you to associate the LDP router ID with a nondefault VRF.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

29

Establishing Nondirectly Connected MPLS LDP Sessions Example

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

30

MPLS LDP Session Protection

The MPLS LDP Session Protection feature provides faster label distribution protocol convergence when a link recovers following an outage. MPLS LDP Session Protection protects a label distribution protocol (LDP) session between directly connected neighbors or an LDP session established for a traffic engineering (TE) tunnel.

• Finding Feature Information, page 31

• Restrictions for MPLS LDP Session Protection, page 31

• Information About MPLS LDP Session Protection, page 31

• How to Configure MPLS LDP Session Protection, page 33

• Configuration Examples for MPLS LDP Session Protection, page 36

• Additional References, page 39

• Command Reference, page 40

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Restrictions for MPLS LDP Session Protection

This feature is not supported under the following circumstances:

• With TDP sessions

• With extended access lists

• With LC-ATM routers

Information About MPLS LDP Session Protection

MPLS LDP Session Protection maintains LDP bindings when a link fails. MPLS LDP sessions are protected through the use of LDP Hello messages. When you enable MPLS LDP, the label switched routers (LSRs) send messages to find other LSRs with which they can create LDP sessions.

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31

Information About MPLS LDP Session Protection

• If the LSR is one hop from its neighbor, it is directly connected to its neighbor. The LSR sends out LDP Hello messages as User Datagram Protocol (UDP) packets to all the routers on the subnet. The hello message is called an LDP Link Hello. A neighboring LSR responds to the hello message and the two routers begin to establish an LDP session.

• If the LSR is more than one hop from its neighbor, it is not directly connected to its neighbor. The LSR sends out a directed hello message as a UDP packet, but as a unicast message specifically addressed to that LSR. The hello message is called an LDP Targeted Hello. The nondirectly connected LSR responds to the Hello message and the two routers establish an LDP session. (If the path between two LSRs has been traffic engineered and has LDP enabled, the LDP session between them is called a targeted session.)

MPLS LDP Session Protection uses LDP Targeted Hellos to protect LDP sessions. Take, for example, two directly connected routers that have LDP enabled and can reach each other through alternate IP routes in the network. An LDP session that exists between two routers is called an LDP Link Hello Adjacency. When MPLS LDP Session Protection is enabled, an LDP Targeted Hello Adjacency is also established for the LDP session. If the link between the two routers fails, the LDP Link Adjacency also fails. However, if the LDP peer is still reachable through IP, the LDP session stays up, because the LDP Targeted Hello Adjacency still exists between the routers. When the directly connected link recovers, the session does not need to be reestablished, and LDP bindings for prefixes do not need to be relearned.

MPLS LDP Session Protection Customizations

• MPLS LDP Session Protection Customizations, page 32

MPLS LDP Session Protection Customizations

You can modify MPLS LDP Session Protection by using the keywords in the mpls ldp session protection command.

Specifying How Long an LDP Targeted Hello Adjacency Should Be Retained

The default behavior of the mpls ldp session protection command allows an LDP Targeted Hello Adjacency to exist indefinitely following the loss of an LDP Link Hello Adjacency. You can issue the duration keyword to specify the number of seconds (from 30 to 2,147,483) that the LDP Targeted Hello Adjacency is retained after the loss of the LDP Link Hello Adjacency. When the link is lost, a timer starts. If the timer expires, the LDP Targeted Hello Adjacency is removed.

Specifying Which Routers Should Have MPLS LDP Session Protection

The default behavior of the mpls ldp session protection command allows MPLS LDP Session Protection for all neighbor sessions. You can issue either the vrfor for keyword to limit the number of neighbor sessions that are protected.

Enabling MPLS LDP Session Protection on Specified VPN Routing and Forwarding Instances

If the router is configured with at least one VPN routing and forwarding (VRF) instance, you can use the vrf keyword to select which VRF is to be protected. You cannot specify more than one VRF with the mpls ldp session protection command. To specify multiple VRFs, issue the command multiple times.

Enabling MPLS LDP Session Protection on Specified Peer Routers

You can create an access list that includes several peer routers. You can specify that access list with the for keyword to enable LDP Session Protection for the peer routers in the access control list.

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How to Configure MPLS LDP Session Protection

• Enabling MPLS LDP Session Protection, page 33

• Verifying MPLS LDP Session Protection, page 35

• Troubleshooting Tips, page 36

Enabling MPLS LDP Session Protection

You use the mpls ldp session protection command to enable MPLS LDP Session Protection. This command enables LDP sessions to be protected during a link failure. By default, the command protects all LDP sessions. The command has several options that enable you to specify which LDP sessions to protect. The vrfkeyword lets you protect LDP sessions for a specified VRF. The for keyword lets you specify a standard IP access control list (ACL) of prefixes that should be protected. The duration keyword enables you to specify how long the router should retain the LDP Targeted Hello Adjacency following the loss of the LDP Link Hello Adjacency.

LSRs must be able to respond to LDP targeted hellos. Otherwise, the LSRs cannot establish a targeted adjacency. All routers that participate in MPLS LDP Session Protection must be enabled to respond to targeted hellos. Both neighbor routers must be configured for session protection or one router must be configured for session protection and the other router must be configured to respond to targeted hellos.

DETAILED STEPS

Command or Action

Step 1

enable

Example:

Router> enable

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

ip cef [distributed]

4.

interface loopback number

5.

ip address {prefix mask}

6.

interface interface

7.

mpls ip

8.

mpls label protocol {ldp | tdp | both}

9.

exit

10.

mpls ldp session protection [vrf vpn-name] [for acl] [duration seconds]

Purpose

Enables privileged EXEC mode.

• Enter your password if prompted.

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How to Configure MPLS LDP Session Protection

Command or Action Purpose

MPLS LDP Session Protection

Step 2

Step 3

Step 4

Step 5

configure terminal

Example:

Router# configure terminal

ip cef [distributed]

Example:

Router(config)# ip cef

interface loopback number

Example:

Router(config)# interface Loopback0

ip address {prefix mask}

Example:

Router(config-if)# ip address 10.25.0.11

255.255.255.255

Enters global configuration mode.

Configures Cisco Express Forwarding.

Configures a loopback interface and enters interface configuration mode.

Assigns an IP address to the loopback interface.

Step 6

Step 7

Step 8

interface interface

Example:

Router(config-if)# interface POS3/0

mpls ip

Example:

Router(config-if)# mpls ip

mpls label protocol {ldp | tdp | both}

Example:

Router(config-if)# mpls label protocol ldp

Specifies the interface to configure.

Configures MPLS hop-by-hop forwarding for a specified interface.

Configures the use of LDP on a specific interface or on all interfaces.

In interface configuration mode, the command sets the default label distribution protocol for the interface to be LDP, overriding any default set by the global mpls label protocolcommand.

In global configuration mode, the command sets all the interfaces to LDP.

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Verifying MPLS LDP Session Protection

Command or Action Purpose

How to Configure MPLS LDP Session Protection

Step 9

exit

Example:

Router(config-if)# exit

Step 10

mpls ldp session protection [vrf vpn-name] [for acl] [duration seconds]

Example:

Router(config)# mpls ldp session protection

Verifying MPLS LDP Session Protection

SUMMARY STEPS

1.

show mpls ldp discovery

2.

show mpls ldp neighbor

3.

show mpls ldp neighbor detail

DETAILED STEPS

Exits from interface configuration mode.

Enables MPLS LDP Session Protection.

Step 1

Step 2

show mpls ldp discovery Issue this command and check that the output contains xmit/recv to the peer router.

Example:

Router# show mpls ldp discovery Local LDP Identifier:

10.0.0.5:0 Discovery Sources: Interfaces: ATM5/1/0.5 (ldp): xmit/recv LDP Id: 10.0.0.1:0 Targeted Hellos:

10.0.0.5 -> 10.0.0.3 (ldp): active, xmit/recv LDP Id: 10.0.0.3:0

show mpls ldp neighbor Issue this command to check that the targeted hellos are active.

Example:

Router# show mpls ldp neighbor Peer LDP Ident: 10.0.0.3:0; Local LDP Ident 10.0.0.5:0 TCP connection: 10.0.0.3.646 - 10.0.0.5.11005 State: Oper; Msgs sent/rcvd: 1453/1464; Downstream

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Configuration Examples for MPLS LDP Session Protection

Up time: 21:09:56 LDP discovery sources: Targeted Hello 10.0.0.5 -> 10.0.0.3, active Addresses bound to peer LDP Ident:

10.3.104.3 10.0.0.2 10.0.0.3

Step 3

show mpls ldp neighbor detail Issue this command to check that the MPLS LDP Session Protection state is Ready or Protecting. If the second last line of the output shows Incomplete, the Targeted Hello Adjacency is not up yet.

Example:

Router# show mpls ldp neighbor detail Peer LDP Ident: 10.16.16.16:0; Local LDP Ident 10.15.15.15:0 TCP connection: 10.16.16.16.11013 - 10.15.15.15.646 State: Oper; Msgs sent/rcvd: 53/51; Downstream; Last TIB rev sent 74 Up time: 00:11:32; UID: 1; Peer Id 0; LDP discovery sources: Targeted Hello 10.15.15.15 -> 10.16.16.16, active, passive; holdtime: infinite, hello interval: 10000 ms Addresses bound to peer LDP Ident:

10.0.0.2 10.16.16.16 10.101.101.101 11.0.0.1 Peer holdtime: 180000 ms; KA interval: 60000 ms; Peer state: estab Clients: Dir Adj Client LDP Session Protection enabled, state: Protecting duration: infinite

Troubleshooting Tips

Use the clear mpls ldp neighbor command if you need to terminate an LDP session after a link goes down. This is useful for situations where the link needs to be taken out of service or needs to be connected to a different neighbor.

To enable the display of events related to MPLS LDP Session Protection, use the debug mpls ldp session protectioncommand.

Configuration Examples for MPLS LDP Session Protection

The figure below shows a sample configuration for MPLS LDP Session Protection.

Figure 3

MPLS LDP Session Protection Example

R1

redundancy no keepalive-enable

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mode hsa ! ip cef distributed no ip domain-lookup multilink bundle-name both mpls label protocol ldp mpls ldp session protection no mpls traffic-eng auto-bw timers frequency 0 tag-switching tdp router-id Loopback0 force ! interface Loopback0 ip address 10.0.0.1 255.255.255.255 no ip directed-broadcast no ip mroute-cache ! interface Multilink4 no ip address no ip directed-broadcast no ip mroute-cache load-interval 30 ppp multilink multilink-group 4 ! interface Ethernet1/0/0 ip address 10.3.123.1 255.255.0.0 no ip directed-broadcast ! interface Ethernet4/0/0 no ip address no ip directed-broadcast shutdown ! interface Ethernet4/0/1 description -- ip address 10.0.0.2 255.255.255.0 no ip address no ip directed-broadcast shutdown ! interface Ethernet4/0/4 ip address 10.0.0.1 255.0.0.0 no ip directed-broadcast mpls label protocol ldp tag-switching ip ! interface Ethernet4/0/6 ip address 10.0.0.1 255.0.0.0 no ip directed-broadcast mpls label protocol ldp tag-switching ip ! interface Ethernet4/0/7 ip address 10.0.0.1 255.0.0.0 no ip directed-broadcast mpls label protocol ldp tag-switching ip ! router ospf 100 log-adjacency-changes redistribute connected network 10.0.0.1 0.0.0.0 area 100 network 10.0.0.0 0.255.255.255 area 100 network 10.0.0.0 0.255.255.255 area 100 network 10.0.0.0 0.255.255.255 area 100 network 10.0.0.0 0.255.255.255 area 100 ! ip classless

Configuration Examples for MPLS LDP Session Protection

R2

redundancy no keepalive-enable mode hsa

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Configuration Examples for MPLS LDP Session Protection

! ip subnet-zero ip cef distributed mpls label protocol ldp mpls ldp session protection no mpls traffic-eng auto-bw timers frequency 0 tag-switching tdp router-id Loopback0 force ! interface Loopback0 ip address 10.0.0.3 255.255.255.255 no ip directed-broadcast ! interface Ethernet5/0/0 no ip address no ip directed-broadcast shutdown full-duplex ! interface Ethernet5/0/2 ip address 10.0.0.1 255.0.0.0 no ip directed-broadcast full-duplex mpls label protocol ldp tag-switching ip ! interface Ethernet5/0/6 ip address 10.0.0.2 255.0.0.0 no ip directed-broadcast ip load-sharing per-packet full-duplex mpls label protocol ldp tag-switching ip ! interface FastEthernet5/1/0 ip address 10.3.123.112 255.255.0.0 no ip directed-broadcast ! router ospf 100 log-adjacency-changes redistribute connected network 10.0.0.3 0.0.0.0 area 100 network 10.0.0.0 0.255.255.255 area 100 network 10.0.0.0 0.255.255.255 area 100 ! ip classless

MPLS LDP Session Protection

R3

ip cef no ip domain-lookup mpls label range 200 100000 static 16 199 mpls label protocol ldp no mpls traffic-eng auto-bw timers frequency 0 tag-switching tdp router-id Loopback0 force ! interface Loopback0 ip address 10.0.0.5 255.255.255.255 no ip directed-broadcast ! interface Ethernet1/0 no ip address no ip directed-broadcast shutdown half-duplex ! interface Ethernet1/2 ip address 10.0.0.2 255.0.0.0 no ip directed-broadcast full-duplex mpls label protocol ldp tag-switching ip !

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interface Ethernet1/4 ip address 10.0.0.2 255.0.0.0 no ip directed-broadcast full-duplex mpls label protocol ldp tag-switching ip ! router ospf 100 log-adjacency-changes redistribute connected network 10.0.0.5 0.0.0.0 area 100 network 10.0.0.0 0.255.255.255 area 100 network 10.0.0.0 0.255.255.255 area 100 ! ip classless

Additional References

Related Documents

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Multiprotocol Label Switching Command Reference at http://www.cisco.com/en/US/docs/ios/mpls/command/reference/mp_book.html . For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/

Support/CLILookup or to the Cisco IOS Master Commands List.

•

debug mpls ldp session protection

•

mpls ldp session protection

•

show mpls ldp neighbor

http://www.cisco.com/techsupport

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

40

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

MPLS LDP Inbound Label Binding Filtering

Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) supports inbound label binding filtering. You can use the MPLS LDP Inbound Label Binding Filtering feature to configure access control lists (ACLs) for controlling the label bindings a label switch router (LSR) accepts from its peer LSRs.

• Finding Feature Information, page 41

• Restrictions, page 41

• Information about MPLS LDP Inbound Label Binding Filtering, page 41

• How to Configure MPLS LDP Inbound Label Binding Filtering, page 42

• Configuration Examples for MPLS LDP Inbound Label Binding Filtering, page 45

• Additional References, page 46

• Feature Information for MPLS LDP Inbound Label Binding Filtering Feature, page 47

• Glossary, page 48

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Restrictions

Inbound label binding filtering does not support extended ACLs; it only supports standard ACLs.

Information about MPLS LDP Inbound Label Binding Filtering

The MPLS LDP Inbound Label Binding Filtering feature may be used to control the amount of memory used to store LDP label bindings advertised by other routers. For example, in a simple MPLS Virtual Private Network (VPN) environment, the VPN provider edge (PE) routers may require LSPs only to their peer PE routers (that is, they do not need LSPs to core routers). Inbound label binding filtering enables a PE router to accept labels only from other PE routers.

MPLS LDP Configuration Guide, Cisco IOS Release 12.4

41

Configuring MPLS LDP Inbound Label Binding Filtering

How to Configure MPLS LDP Inbound Label Binding Filtering

• Configuring MPLS LDP Inbound Label Binding Filtering, page 42

• Verifying that MPLS LDP Inbound Label Bindings are Filtered, page 44

Configuring MPLS LDP Inbound Label Binding Filtering

Perform this task to configure a router for inbound label filtering. The following configuration allows the router to accept only the label for prefix 25.0.0.2 from LDP neighbor router 10.12.12.12.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

ip access-list standard access-list-number

4.

permit {source [source-wildcard] | any} [log]

5.

exit

6.

mpls ldp neighbor [vrf vpn-name] nbr-address labels accept acl

7.

end

DETAILED STEPS

Command or Action

Step 1

Step 2

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

Purpose

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

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Command or Action Purpose

How to Configure MPLS LDP Inbound Label Binding Filtering

Step 3

Step 4

Step 5

ip access-list standard access-list-number

Example:

Router(config)# ip access-list standard 1

permit {source [source-wildcard] | any} [log]

Example:

Router(config-std-nacl)# permit 10.0.0.0

exit

Example:

Defines a standard IP access list with a number.

Specifies one or more prefixes permitted by the access list.

Exits the current mode and goes to the next higher level.

Step 6

Step 7

Example:

Router(config-std-nacl)# exit

mpls ldp neighbor [vrf vpn-name] nbr-address labels accept acl

Example:

Router(config)# mpls ldp neighbor 10.12.12.12 labels accept 1

end

Example:

Router(config)# end

Specifies the ACL to be used to filter label bindings for the specified LDP neighbor.

Exits the current mode and enters privileged Exec mode.

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Verifying that MPLS LDP Inbound Label Bindings are Filtered

How to Configure MPLS LDP Inbound Label Binding Filtering

Verifying that MPLS LDP Inbound Label Bindings are Filtered

If inbound filtering is enabled, perform the following steps to verify that inbound label bindings are filtered:

SUMMARY STEPS

1.

Enter the show mpls ldp neighbor command to show the status of the LDP session, including the name or number of the ACL configured for inbound filtering.

2.

Enter the show ip access-list command to display the contents of all current IP access lists or of a specified access list.

3.

Enter the show mpls ldp bindingscommand to verify that the LSR has remote bindings only from a specified peer for prefixes permitted by the access list.

DETAILED STEPS

Step 1

Step 2

Enter the show mpls ldp neighbor command to show the status of the LDP session, including the name or number of the ACL configured for inbound filtering.

Example:

show mpls ldp neighbor

[vrf

vpn-name ][ address | interface ] [detail

To display information about inbound label binding filtering, you must enter the detail keyword.

Note

Following is sample output from the show mpls ldp neighbor command.

Example:

Router# show mpls ldp neighbor 10.12.12.12 detail Peer LDP Ident: 10.12.12.12:0; Local LDP Ident 10.13.13.13:0 TCP connection: 10.12.12.12.646 - 10.13.13.13.12592 State: Oper; Msgs sent/rcvd: 49/45; Downstream; Last TIB rev sent 1257 Up time: 00:32:41; UID: 1015; Peer Id 0; LDP discovery sources: Serial1/0; Src IP addr: 25.0.0.2 holdtime: 15000 ms, hello interval: 5000 ms Addresses bound to peer LDP Ident:

10.0.0.129 10.12.12.12 10.0.0.2 Peer holdtime: 180000 ms; KA interval: 60000 ms; Peer state: estab LDP inbound filtering accept acl: 1

Enter the show ip access-list command to display the contents of all current IP access lists or of a specified access list.

Example:

show ip access-list

[

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MPLS LDP Inbound Label Binding Filtering

access-list-number | access-list-name ]

It is important that you enter this command to see how the access list is defined; otherwise, you cannot verify

Note

inbound label binding filtering.

The following command output shows the contents of IP access list 1:

Example:

Router# show ip access 1 Standard IP access list 1 permit 10.0.0.0, wildcard bits 0.0.0.255 (1 match)

Step 3

Enter the show mpls ldp bindingscommand to verify that the LSR has remote bindings only from a specified peer for prefixes permitted by the access list.

Example:

Configuration Examples for MPLS LDP Inbound Label Binding Filtering

Router# show mpls ldp bindings tib entry: 10.0.0.0/8, rev 4 local binding: tag: imp-null tib entry: 10.2.0.0/16, rev 1137 local binding: tag: 16 tib entry: 10.2.0.0/16, rev 1139 local binding: tag: 17 tib entry: 10.12.12.12/32, rev 1257 local binding: tag: 18 tib entry: 10.13.13.13/32, rev 14 local binding: tag: imp-null tib entry: 10.10.0.0/16, rev 711 local binding: tag: imp-null tib entry: 10.0.0.0/8, rev 1135 local binding: tag: imp-null remote binding: tsr: 12.12.12.12:0, tag: imp-null tib entry: 10.0.0.0/8, rev 8 local binding: tag: imp-null Router#

Configuration Examples for MPLS LDP Inbound Label Binding Filtering

In the following example, the mpls ldp neighbor labels accept command is configured with an access control list to filter label bindings received on sessions with the neighbor 10.110.0.10.

Label bindings for prefixes that match 10.b.c.d are accepted, where b is less than or equal to 63, and c and d can be any integer between 0 and 128. Other label bindings received from 10.110.0.10 are rejected.

Router# configure terminal Router(config)# access-list 1 permit 10.63.0.0 0.63.255.255

Router(config)# mpls ldp neighbor 10.110.0.10 labels accept 1

Router(config)# end

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Additional References

In the following example, the show mpls ldp bindings neighborcommand displays label bindings that were learned from 10.110.0.10. This example verifies that the LIB does not contain label bindings for prefixes that have been excluded.

Router# show mpls ldp bindings neighbor 10.110.0.10 tib entry: 10.2.0.0/16, rev 4 remote binding: tsr: 10.110.0.10:0, tag: imp-null tib entry: 10.43.0.0/16, rev 6 remote binding: tsr: 10.110.0.10:0, tag: 16 tib entry: 10.52.0.0/16, rev 8 remote binding: tsr: 10.110.0.10:0, tag: imp-null

Additional References

Related Documents

Feature Information for MPLS LDP Inbound Label Binding Filtering Feature

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

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Glossary

MPLS LDP Inbound Label Binding Filtering

Table 3 Feature Information for MPLS LDP Inbound Label Binding Filtering Feature

Feature Name Releases Feature Information

MPLS LDP Inbound Label Binding Filtering Feature

12.0(26)S

12.2(25)S

12.3(14)T

12.2(18)SXE

You can use the MPLS LDP Inbound Label Binding Filtering feature to configure access control lists (ACLs) for controlling the label bindings a label switch router (LSR) accepts from its peer LSRs.

In Cisco IOS Release 12.0(26)S, this feature was introduced on the Cisco 7200.

This feature was integrated into Cisco IOS Release 12.2(25)S for the Cisco 7500 series router.

This feature was integrated into Cisco IOS Release 12.3(14)T.

This feature was integrated into Cisco IOS Release 12.2(18)SXE for the Cisco 7600 series router.

The following commands were introduced or modified:

•

clear mpls ldp neighbor

•

mpls ldp neighbor labels accept

•

show mpls ldp neighbor

Glossary

carrier supporting carrier --A situation where one service provider allows another service provider to use a segment of its backbone network. The service provider that provides the segment of the backbone network to the other provider is called the backbone carrier. The service provider that uses the segment of the backbone network is called the customer carrier.

CE router --customer edge router. A router that is part of a customer network and that interfaces to a provider edge (PE) router.

inbound label binding filtering --Allows LSRs to control which label bindings it will accept from its neighboring LSRs. Consequently, an LSR does not accept or store some label bindings that its neighbors advertise.

label --A short fixed-length identifier that tells switching nodes how to forward data (packets or cells). label binding --An association between a destination prefix and a label.

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MPLS LDP Inbound Label Binding Filtering

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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Verifying that MPLS LDP Inbound Label Bindings are Filtered

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MPLS LDP Autoconfiguration

The MPLS LDP Autoconfiguration feature enables you to globally configure Label Distribution Protocol (LDP) on every interface associated with a specified Interior Gateway Protocol (IGP) instance.

• Finding Feature Information, page 51

• Restrictions for MPLS LDP Autoconfiguration , page 51

• Information About MPLS LDP Autoconfiguration, page 52

• How to Configure MPLS LDP Autoconfiguration, page 52

• Configuration Examples for MPLS LDP Autoconfiguration, page 61

• Additional References, page 62

• Feature Information for MPLS LDP Autoconfiguration, page 63

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Restrictions for MPLS LDP Autoconfiguration

•

In Cisco IOS Release 12.0(32)SY, the mpls ldp autoconfig command is supported only with OSPF. Other IGPs are not supported.

•

If LDP is disabled globally, the mpls ldp autoconfigcommand fails and generates a console message explaining that LDP must first be enabled globally by means of the global mpls ip command.

•

If the mpls ldp autoconfig command is configured for an IGP instance, you cannot issue the global no mpls ip command. To disable LDP, you must first issue the no mpls ldp autoconfig command.

• For interfaces running IS-IS processes, you can enable Multiprotocol Label Switching (MPLS) for

each interface, using the router mode command mpls ldp autoconfig or mpls ldp igp autoconfig at the interface level.

• You specify that the default label distribution protocol is LDP for a router or for an interface. Tag

Distribution Protocol (TDP) is not supported.

• The MPLS LDP Autoconfiguration feature is not supported on traffic engineering tunnel interfaces.

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MPLS LDP Autoconfiguration on OSPF and IS-IS Interfaces

Information About MPLS LDP Autoconfiguration

To enable LDP, you should configure it globally and on each interface where it is needed. Configuring LDP on many interfaces can be time-consuming. The following section provides information about autoconfiguration feature on OSPF and IS-IS interfaces:

• MPLS LDP Autoconfiguration on OSPF and IS-IS Interfaces, page 52

MPLS LDP Autoconfiguration on OSPF and IS-IS Interfaces

The MPLS LDP Autoconfiguration feature enables you to globally enable LDP on every interface associated with an IGP instance. This feature is supported on OSPF and IS-IS IGPs. It provides a means to block LDP from being enabled on interfaces that you do not want enabled. The goal of the MPLS LDP Autoconfiguration feature is to make configuration easier, faster, and error free.

You issue the mpls ldp autoconfigcommand to enable LDP on each interface that is running an OSPF or IS-IS process. If you do not want some of the interfaces to have LDP enabled, you can issue the no form of the mpls ldp igp autoconfig command on those interfaces.

How to Configure MPLS LDP Autoconfiguration

• Configuring MPLS LDP Autoconfiguration with OSPF Interfaces, page 52

• Disabling MPLS LDP Autoconfiguration from Selected OSPF Interfaces, page 54

• Verifying MPLS LDP Autoconfiguration with OSPF, page 55

• Configuring MPLS LDP Autoconfiguration with IS-IS Interfaces, page 57

• Disabling MPLS LDP Autoconfiguration from Selected IS-IS Interfaces, page 59

• Verifying MPLS LDP Autoconfiguration with IS-IS, page 60

Configuring MPLS LDP Autoconfiguration with OSPF Interfaces

The following steps explain how to configure LDP for interfaces running OSPF processes.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

mpls ip

4.

mpls label protocol ldp

5.

interface type number

6.

ip address prefix mask

7.

exit

8.

router ospf process-id

9.

network ip-address wildcard-mask area area-id

10.

mpls ldp autoconfig [area area-id]

11.

end

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DETAILED STEPS

Command or Action Purpose

How to Configure MPLS LDP Autoconfiguration

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

mpls ip

Example:

Router(config)# mpls ip

mpls label protocol ldp

Example:

Router(config)# mpls label protocol ldp

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Globally enables hop-by-hop forwarding.

Specifies LDP as the default label distribution protocol.

Step 5

Step 6

Step 7

interface type number

Example:

Router(config)# interface POS 3/0

ip address prefix mask

Example:

Router(config-if)# ip address 10.0.0.11

255.255.255.255

exit

Example:

Router(config-if)# exit

Specifies the interface to configure and enters interface configuration mode.

Assigns an IP address to the interface.

Exits interface configuration mode.

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Command or Action Purpose

Disabling MPLS LDP Autoconfiguration from Selected OSPF Interfaces

Step 8

Step 9

Step 10

Step 11

router ospf process-id

Example:

Router(config)# router ospf 1

network ip-address wildcard-mask area area-id

Example:

Router(config-router)# network 10.0.0.0

0.0.255.255 area 3

mpls ldp autoconfig [area area-id]

Example:

Router(config-router)# mpls ldp autoconfig area 3

end

Example:

Enables OSPF routing and enters router configuration mode.

Specifies the interface on which OSPF runs and defines the area ID for that interface.

Enables the MPLS LDP Autoconfiguration feature to enable LDP on interfaces belonging to an OSPF process.

• If no area is specified, the command applies to all interfaces associated with the OSPF process. If an area ID is specified, then only interfaces associated with that OSPF area are enabled with LDP.

Exits router configuration mode and returns to privileged EXEC mode.

Router(config-router)# end

Disabling MPLS LDP Autoconfiguration from Selected OSPF Interfaces

When you issue the mpls ldp autoconfig command, all the interfaces that belong to an OSPF area are enabled for LDP. To remove LDP from some interfaces, use the no mpls ldp igp autoconfigcommand on those interfaces. The following configuration steps show how to disable LDP from some of the interfaces after they were configured with the MPLS LDP Autoconfiguration feature with the mpls ldp autoconfig command.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

interface type number

4.

no mpls ldp igp autoconfig

5.

end

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Verifying MPLS LDP Autoconfiguration with OSPF

DETAILED STEPS

Command or Action Purpose

How to Configure MPLS LDP Autoconfiguration

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

interface type number

Example:

Router(config)# interface POS 3/0

no mpls ldp igp autoconfig

Example:

Router(config-if)# no mpls ldp igp autoconfig

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Specifies the interface to configure and enters interface configuration mode.

Disables LDP for that interface.

Step 5

end

Exits interface configuration mode and returns to privileged EXEC mode.

Example:

Router(config-if)# end

Verifying MPLS LDP Autoconfiguration with OSPF

The following steps explain how to verify the MPLS LDP Autoconfiguration feature.

SUMMARY STEPS

1.

enable

2.

show mpls interfaces [type number | vrf vpn-name][all] [detail] [internal]

3.

show mpls ldp discovery [vrf vpn-name | all] [detail]

DETAILED STEPS

Step 1

enable

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How to Configure MPLS LDP Autoconfiguration

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

show mpls interfaces [type number | vrf vpn-name][all] [detail] [internal] The show mpls interfaces command displays the method used to enable LDP on an interface:

•

If LDP is enabled by the mpls ldp autoconfigcommand, the output displays:

Example:

IP labeling enabled (ldp): IGP config

•

If LDP is enabled by the mpls ip command, the output displays:

Example:

IP labeling enabled (ldp): Interface config

MPLS LDP Autoconfiguration

Step 3

•

If LDP is enabled by the mpls ip command and the mpls ldp autoconfig command, the output displays:

Example:

IP labeling enabled (ldp): Interface config IGP config

The following example shows that LDP was enabled on the interface by both the mpls ip and mpls ldp autoconfig commands:

Example:

Router# show mpls interfaces Serial 2/0 detail

Interface Serial2/0: IP labeling enabled (ldp): Interface config IGP config LSP Tunnel labeling enabled BGP labeling not enabled MPLS operational Fast Switching Vectors: IP to MPLS Fast Switching Vector MPLS Turbo Vector MTU = 1500

show mpls ldp discovery [vrf vpn-name | all] [detail] The show mpls ldp discovery detailcommand alsoshows how LDP was enabled on the interface. In the following example, LDP was enabled by both the mpls ip and mpls ldp autoconfig commands:

Example:

Router# show mpls ldp discovery detail Local LDP Identifier:

10.11.11.11:0 Discovery Sources: Interfaces:

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Configuring MPLS LDP Autoconfiguration with IS-IS Interfaces

How to Configure MPLS LDP Autoconfiguration

Serial2/0 (ldp): xmit/recv Enabled: Interface config, IGP config; Hello interval: 5000 ms; Transport IP addr: 10.11.11.11 LDP Id: 10.10.10.10:0 Src IP addr: 10.0.0.1; Transport IP addr: 10.10.10.10 Hold time: 15 sec; Proposed local/peer: 15/15 sec

Configuring MPLS LDP Autoconfiguration with IS-IS Interfaces

The following steps explain how to configure the MPLS LDP Autoconfiguration feature for interfaces that are running IS-IS processes.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

interface type number

4.

ip address prefix mask

5.

ip router isis

6.

exit

7.

mpls ip

8.

mpls label protocol ldp

9.

router isis

10.

mpls ldp autoconfig [level-1 | level-2]

11.

end

DETAILED STEPS

Command or Action

Step 1

Step 2

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

Purpose

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

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How to Configure MPLS LDP Autoconfiguration

Command or Action Purpose

MPLS LDP Autoconfiguration

Step 3

Step 4

Step 5

Step 6

interface type number

Example:

Router(config)# interface POS 0/2

ip address prefix mask

Example:

Router(config-if)# ip address 10.50.72.4 255.0.0.0

ip router isis

Example:

Router(config-if)# ip router isis

exit

Example:

Router(config-if)# exit

Specifies the interface to configure and enters interface configuration mode.

Assigns an IP address to the interface.

Enables IS-IS for IP on the interface.

Exits interface configuration mode.

Step 7

Step 8

Step 9

mpls ip

Example:

Router(config)# mpls ip

mpls label protocol ldp

Example:

Router(config)# mpls label protocol ldp

router isis

Example:

Router(config)# router isis

Globally enables hop-by-hop forwarding.

Specifies LDP as the default label distribution protocol.

Enables an IS-IS process on the router and enters router configuration mode.

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Disabling MPLS LDP Autoconfiguration from Selected IS-IS Interfaces

Command or Action Purpose

How to Configure MPLS LDP Autoconfiguration

Step 10

mpls ldp autoconfig [level-1 | level-2]

Enables the LDP for interfaces that belong to an IS-IS process.

Example:

Router(config-router)# mpls ldp autoconfig

Step 11

end

Exits router configuration mode and returns to privileged EXEC mode.

Example:

Router(config-router)# end

Disabling MPLS LDP Autoconfiguration from Selected IS-IS Interfaces

When you issue the mpls ldp autoconfig command, all the interfaces that belong to an IS-IS process are enabled for LDP. To remove LDP from some interfaces, use the no mpls ldp igp autoconfig command on those interfaces. The following configuration steps show how to disable LDP from some of the interfaces after they were configured with the MPLS LDP Autoconfiguration feature with the mpls ldp autoconfig command.

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

interface type number

4.

no mpls ldp igp autoconfig

5.

end

DETAILED STEPS

Purpose

Enables privileged EXEC mode.

Step 1

Command or Action

enable

• Enter your password if prompted.

Example:

Router> enable

Step 2

59

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

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How to Configure MPLS LDP Autoconfiguration

Command or Action Purpose

Verifying MPLS LDP Autoconfiguration with IS-IS

Step 3

interface type number

Specifies the interface to configure and enters interface configuration mode.

Example:

Router(config)# interface POS 3/0

Step 4

no mpls ldp igp autoconfig

Disables LDP for that interface.

Example:

Router(config-if)# no mpls ldp igp autoconfig

Step 5

end

Exits interface configuration mode and returns to privileged EXEC mode.

Example:

Router(config-if)# end

Verifying MPLS LDP Autoconfiguration with IS-IS

You can verify that the MPLS LDP Autoconfiguration feature is working correctly with the show isis mpls ldp command.

Step 1

Step 2

SUMMARY STEPS

1.

enable

2.

show isis mpls ldp

DETAILED STEPS

enable

Enables privileged EXEC mode. show isis mpls ldp

The output of the following show isis mpls ldp command shows that IS-IS is configured on the interface and that LDP is enabled:

Example:

Router# show isis mpls ldp Interface: POS0/2; ISIS tag null enabled ISIS is UP on interface AUTOCONFIG Information : LDP enabled: YES SYNC Information : Required: NO

The output shows :

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MPLS LDP Autoconfiguration with OSPF Example

• IS-IS is up.

• LDP is enabled.

If the MPLS LDP Autoconfiguration feature is not enabled on an interface, the output looks like the following:

Example:

Interface: Ethernet0; ISIS tag null enabled ISIS is UP on interface AUTOCONFIG Information : LDP enabled: NO SYNC Information : Required: NO

• Troubleshooting Tips, page 61

Troubleshooting Tips

You can use the debug mpls ldp autoconfigcommand to display events that are related to the MPLS LDP Autoconfiguration feature.

Configuration Examples for MPLS LDP Autoconfiguration

The following sections show examples for the MPLS LDP Autoconfiguration feature with OSPF and IS-IS processes.

• MPLS LDP Autoconfiguration with OSPF Example, page 61

• MPLS LDP Autoconfiguration with IS-IS Examples, page 62

MPLS LDP Autoconfiguration with OSPF Example

The following configuration commands enable LDP for OSPF process 1 area 3. The mpls ldp autoconfig area 3 command and the OSPF network commands enable LDP on POS interfaces 0/0, 0/1, and 1/1. The no mpls ldp igp autoconfig command on POS interface 1/0 prevents LDP from being enabled on POS

interface 1/0, even though OSPF is enabled for that interface.

configure terminal interface POS 0/0 ip address 10.0.0.1 255.0.0.0 ! interface POS 0/1 ip address 10.0.1.1 255.0.0.1 ! interface POS 1/1 ip address 10.1.1.1 255.255.0.0 ! interface POS 1/0 ip address 10.1.0.1 0.1.0.255 exit ! router ospf 1 network 10.0.0.0 0.0.255.255 area 3 network 10.1.0.0 0.0.255.255 area 3

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Additional References

mpls ldp autoconfig area 3 end interface POS 1/0 no mpls ldp igp autoconfig

MPLS LDP Autoconfiguration with IS-IS Examples

The following example shows the configuration of the MPLS LDP Autoconfiguration feature on POS0/2 and 0/3 interfaces, which are running IS-IS processes:

configure terminal interface POS 0/2 ip address 10.0.0.1 255.0.0.1 ip router isis ! interface POS 0/3 ip address 10.1.1.1 255.0.1.0 ip router isis exit

mpls ip

MPLS LDP Autoconfiguration with IS-IS Examples

mpls label protocol ldp

router isis

mpls ldp autoconfig

Additional References

The following sections provide references related to the MPLS LDP Autoconfiguration feature.

Related Documents

Feature Information for MPLS LDP Autoconfiguration

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

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MPLS LDP Autoconfiguration

Table 4 Feature Information for MPLS LDP Autoconfiguration

Feature Name Releases Feature Information

MPLS LDP Autoconfiguration 12.0(30)S 12.0(32)SY

12.2(28)SB 12.2(33)SRB

12.3(14)T 15.0(1)M

12.2(33)XNE

This feature enables you to globally configure LDP on every interface associated with a specified Interior Gateway Protocol (IGP) instance.

In Cisco IOS Release 12.0(30)S, this feature was introduced with support for OSPF.

In Cisco IOS Release

12.0(32)SY, support for IS-IS was added.

This feature was integrated into Cisco IOS Release 12.2(28)SB with support for OSPF.

This feature was integrated into Cisco IOS Release 12.2(33)SRB.

This feature was integrated into Cisco IOS Release 12.3(14)T with support for OSPF.

In Release 15.0(1)M, support for IS-IS was added.

This feature was integrated into Cisco IOS Release 12.2(33)XNE with support for IS-IS on the Cisco 10000 series router.

The following commands were modified: mpls ldp autoconfig,

mpls ldp igp autoconfig, show isis mpls ldp, and show mpls ldp discovery.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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When a router is configured with Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) Graceful Restart (GR), it assists a neighboring router that has MPLS LDP Stateful Switchover/ Nonstop Forwarding (SSO/NSF) Support and Graceful Restart to recover gracefully from an interruption in service. In this Cisco IOS release, MPLS LDP GR functions strictly in helper mode, which means it can only help other routers that are enabled with MPLS SSO/NSF and GR to recover. If the router with LDP GR fails, its peer routers cannot help it recover.

Notes:

• MPLS LDP SSO/NSF Support and Graceful Restart is supported in Cisco IOS Release 12.2(25)S. For brevity, this feature is called LDP SSO/NSF in this document.

• The MPLS LDP GR feature described in this document refers to helper mode.

When you enable MPLS LDP GR on a router that peers with an MPLS LDP SSO/NSF-enabled router, the SSO/NSF-enabled router can maintain its forwarding state when the LDP session between them is interrupted. While the SSO/NSF-enabled router recovers, the peer router forwards packets using stale information. This enables the SSO/NSF-enabled router to become operational more quickly.

• Finding Feature Information, page 65

• Restrictions, page 65

• Information About MPLS LDP Graceful Restart, page 66

• How to Configure MPLS LDP Graceful Restart, page 67

• Configuration Example for MPLS LDP Graceful Restart, page 69

• Additional References, page 72

• Feature Information for MPLS LDP Graceful Restart, page 73

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Restrictions

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How MPLS LDP Graceful Restart Works

Information About MPLS LDP Graceful Restart

• MPLS LDP GR is supported in strict helper mode.

• Tag Distribution Protocol (TDP) sessions are not supported. Only LDP sessions are supported.

• MPLS LDP GR cannot be configured on label-controlled ATM (LC-ATM) interfaces.

• MPLS LDP SSO/NSF is supported in IOS Release 12.2(25)S. It is not supported in this release.

Information About MPLS LDP Graceful Restart

• How MPLS LDP Graceful Restart Works, page 66

• How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart, page 67

• What Happens If a Route Processor Does Not Have LDP Graceful Restart, page 67

How MPLS LDP Graceful Restart Works

MPLS LDP GR works in strict helper mode, which means it helps a neighboring route processor that has MPLS LDP SSO/NSF to recover from disruption in service without losing its MPLS forwarding state. The disruption in service could be the result of a TCP or UDP event or the stateful switchover of a route processor. When the neighboring router establishes a new session, the LDP bindings and MPLS forwarding states are recovered.

In the topology shown in the figure below, the following elements have been configured:

• LDP sessions are established between Router 1 and Router 2, as well as between Router 2 and Router

3.

• Router 2 has been configured with MPLS LDP SSO/NSF. Routers 1 and 3 have been configured with MPLS LDP GR.

• A label switched path (LSP) has been established between Router 1 and Router 3.

Figure 4

The following process shows how Routers 1 and 3, which have been configured with LDP GR help Router 2, which has been configured with LDP SSO/NSF recover from a disruption in service:

Router 1 notices an interruption in service with Router 2. (Router 3 also performs the same actions in

1

this process.) Router 1 marks all the label bindings from Router 2 as stale, but it continues to use the bindings for

2

MPLS forwarding.

Router 1 reestablishes an LDP session with Router 2, but keeps its stale label bindings. If you issue a show mpls ldp neighbor command with the graceful-restart keyword, the command output displays the recovering LDP sessions.

Both routers readvertise their label binding information. If Router 1 relearns a label from Router 2 after

1

the session has been established, the stale flags are removed. The show mpls forwardingtablecommand displays the information in the MPLS forwarding table, including the local label,

outgoing label or VC, prefix, label-switched bytes, outgoing interface, and next hop.

Example of a Network Using LDP Graceful Restart

You can set various graceful restart timers. See the following commands for more information:

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How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart

How to Configure MPLS LDP Graceful Restart

•

mpls ldp graceful-restart timers neighbor-liveness

•

mpls ldp graceful-restart timers max-recovery

How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart

A route processor that is configured to perform MPLS LDP GR includes the Fault Tolerant (FT) Type Length Value (TLV) in the LDP initialization message. The route processor sends the LDP initialization message to a neighbor to establish an LDP session.

The FT session TLV includes the following information:

• The Learn from Network (L) flag is set to 1, which indicates that the route processor is configured to

perform MPLS LDP GR.

• The Reconnect Timeout field shows the time (in milliseconds) that the neighbor should wait for a

reconnection if the LDP session is lost. In this release, the timer is set to 0, which indicates that if the local router fails, its peers should not wait for it to recover. The timer setting indicates that the local router is working in helper mode.

• The Recovery Time field shows the time (in milliseconds) that the neighbor should retain the MPLS

forwarding state during a recovery. If a neighbor did not preserve the MPLS forwarding state before the restart of the control plane, the neighbor sets the recovery time to 0.

What Happens If a Route Processor Does Not Have LDP Graceful Restart

If two route processors establish an LDP session and one route processor is not configured for MPLS LDP GR, the two route processors create a normal LDP session but do not have the ability to perform MPLS LDP GR. Both route processors must be configured for MPLS LDP GR.

How to Configure MPLS LDP Graceful Restart

• Configuring MPLS LDP Graceful Restart, page 67

• Verifying the Configuration, page 69

Configuring MPLS LDP Graceful Restart

You must enable MPLS LDP GR on all route processors for an LDP session to be preserved during an interruption in service.

MPLS LDP GR is enabled globally. When you enable MPLS LDP GR, it has no effect on existing LDP sessions. New LDP sessions that are established can perform MPLS LDP GR.

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How to Configure MPLS LDP Graceful Restart

SUMMARY STEPS

1.

enable

2.

configure terminal

3.

ip cef [distributed]

4.

mpls ldp graceful-restart

5.

interface type slot/port

6.

mpls ip

7.

mpls label protocol {ldp| tdp| both}

DETAILED STEPS

Command or Action Purpose

MPLS LDP Graceful Restart

Step 1

Step 2

Step 3

Step 4

enable

Example:

Router> enable

configure terminal

Example:

Router# configure terminal

ip cef [distributed]

Example:

Router(config)# ip cef distributed

mpls ldp graceful-restart

Example:

Router(config)# mpls ldp graceful-restart

Enables privileged EXEC mode.

• Enter your password if prompted.

Enters global configuration mode.

Enables Cisco Express Forwarding (CEF).

Enables the router to protect the LDP bindings and MPLS forwarding state during a disruption in service.

Step 5

interface type slot/port

Example:

Router(config)# interface pos 3/0

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Specifies an interface and enters interface configuration mode.

Verifying the Configuration

Command or Action Purpose

Configuration Example for MPLS LDP Graceful Restart

Step 6

Step 7

mpls ip

Example:

Router(config-if)# mpls ip

mpls label protocol {ldp| tdp| both}

Example:

Router(config-if)# mpls label protocol ldp

Note You can also issue the mpls label protocol ldp command in global configuration mode, which enables

LDP on all interfaces configured for MPLS.

Verifying the Configuration

The following commands help verify that MPLS LDP GR has been configured correctly:

mpls ldp neighbor with the graceful-restart

show

keyword

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

Configures the use of LDP for an interface. You must use LDP.

Displays the Graceful Restart information for LDP sessions.

show mpls ldp graceful-restart

Displays Graceful Restart sessions and session parameters.

Configuration Example for MPLS LDP Graceful Restart

The figure below shows a configuration where MPLS LDP GR is enabled on Router 1 and MPLS LDP SSO/NSF is enabled on Routers 2 and 3. In this configuration example, Router 1 creates an LDP session with Router 2. Router 1 also creates a targeted session with Router 3 through a traffic engineering tunnel using Router 2.

Note

MPLS LDP SSO/NSF is supported in Cisco IOS Release 12.2(25)S. It is not supported in this release.

Figure 5 MPLS LDP Graceful Restart Configuration Example

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Configuration Example for MPLS LDP Graceful Restart

Router 1 configured with LDP GR:

boot system slot0:rsp-pv-mz hw-module slot 2 image slot0:rsp-pv-mz hw-module slot 3 image slot0:rsp-pv-mz

! ip subnet-zero ip cef mpls label range 16 10000 static 10001 1048575 mpls label protocol ldp mpls ldp logging neighbor-changes

mpls ldp graceful-restart

mpls traffic-eng tunnels no mpls traffic-eng auto-bw timers frequency 0 mpls ldp router-id Loopback0 force ! interface Loopback0 ip address 20.20.20.20 255.255.255.255 no ip directed-broadcast no ip mroute-cache ! interface Tunnel1 ip unnumbered Loopback0 no ip directed-broadcast mpls label protocol ldp mpls ip tunnel destination 19.19.19.19 tunnel mode mpls traffic-eng tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng priority 7 7 tunnel mpls traffic-eng bandwidth 500 tunnel mpls traffic-eng path-option 1 dynamic ! interface ATM5/1/0 no ip address no ip directed-broadcast atm clock INTERNAL no atm enable-ilmi-trap no atm ilmi-keepalive ! interface ATM5/1/0.5 point-to-point ip address 12.0.0.2 255.0.0.0 no ip directed-broadcast no atm enable-ilmi-trap pvc 6/100 encapsulation aal5snap mpls label protocol ldp mpls traffic-eng tunnels mpls ip ip rsvp bandwidth 1000 ! router ospf 100 log-adjacency-changes redistribute connected network 12.0.0.0 0.255.255.255 area 100 network 20.20.20.20 0.0.0.0 area 100 mpls traffic-eng router-id Loopback0 mpls traffic-eng area 100

MPLS LDP Graceful Restart

Router 2 configured with LDP SSO/NSF:

boot system slot0:rsp-pv-mz hw-module slot 2 image slot0:rsp-pv-mz hw-module slot 3 image slot0:rsp-pv-mz redundancy mode sso

! ip cef no ip domain-lookup mpls label range 17 10000 static 10001 1048575 mpls label protocol ldp

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mpls ldp logging neighbor-changes

mpls ldp graceful-restart

mpls traffic-eng tunnels no mpls traffic-eng auto-bw timers frequency 0 no mpls advertise-labels mpls ldp router-id Loopback0 force ! interface Loopback0 ip address 17.17.17.17 255.255.255.255 no ip directed-broadcast ! interface ATM4/0/0 no ip address no ip directed-broadcast no ip mroute-cache atm clock INTERNAL atm sonet stm-1 no atm enable-ilmi-trap no atm ilmi-keepalive ! interface ATM4/0/0.5 point-to-point ip address 12.0.0.1 255.0.0.0 no ip directed-broadcast no atm enable-ilmi-trap pvc 6/100 encapsulation aal5snap mpls label protocol ldp mpls traffic-eng tunnels mpls ip ip rsvp bandwidth 1000 ! interface POS5/1/0 ip address 11.0.0.1 255.0.0.0 no ip directed-broadcast encapsulation ppp mpls label protocol ldp mpls traffic-eng tunnels mpls ip no peer neighbor-route clock source internal ip rsvp bandwidth 1000 ! router ospf 100 log-adjacency-changes redistribute connected nsf enforce global network 11.0.0.0 0.255.255.255 area 100 network 12.0.0.0 0.255.255.255 area 100 network 17.17.17.17 0.0.0.0 area 100 mpls traffic-eng router-id Loopback0 mpls traffic-eng area 100 ! ip classless

Configuration Example for MPLS LDP Graceful Restart

Router 3 configured with LDP SSO/NSF:

boot system slot0:rsp-pv-mz hw-module slot 2 image slot0:rsp-pv-mz hw-module slot 3 image slot0:rsp-pv-mz redundancy mode sso

! ip subnet-zero ip cef ! no ip finger no ip domain-lookup mpls label protocol ldp mpls ldp neighbor 11.11.11.11 targeted ldp mpls ldp logging neighbor-changes

mpls ldp graceful-restart

mpls traffic-eng tunnels

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Additional References

MPLS LDP Graceful Restart

no mpls traffic-eng auto-bw timers frequency 0 mpls ldp discovery directed-hello interval 12 mpls ldp discovery directed-hello holdtime 130 mpls ldp discovery directed-hello accept mpls ldp router-id Loopback0 force ! interface Loopback0 ip address 19.19.19.19 255.255.255.255 no ip directed-broadcast ! interface POS1/0 ip address 11.0.0.2 255.0.0.0 no ip directed-broadcast encapsulation ppp mpls label protocol ldp mpls traffic-eng tunnels mpls ip no peer neighbor-route clock source internal ip rsvp bandwidth 1000 ! router ospf 100 log-adjacency-changes redistribute connected nsf enforce global network 11.0.0.0 0.255.255.255 area 100 network 19.19.19.19 0.0.0.0 area 100 mpls traffic-eng router-id Loopback0 mpls traffic-eng area 100 ! ip classless

Additional References

Related Documents

Feature Information for MPLS LDP Graceful Restart

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

2

Not all supported RFCs are listed.

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MPLS LDP Graceful Restart

Table 5 Feature Information for MPLS LDP Graceful Restart

Feature Name Releases Feature Information

MPLS LDP Graceful Restart 12.0(29)S 12.3(14)T

12.2(33)SRA

MPLS LDP Graceful Restart assists a neighboring router that has MPLS LDP Stateful Switchover/Nonstop Forwarding (SSO/NSF) Support and Graceful Restart to recover gracefully from an interruption in service.

In Cisco IOS Release 12.0(29)S, this feature was introduced.

This feature was integrated into Cisco IOS Release 12.3(14)T.

This feature was integrated into Cisco IOS Release 12.2(33)SRA.

The following sections provide information about this feature:

The following commands were introduced or modified:

•

debug mpls ldp gracefulrestart

•

mpls ldp graceful-restart

•

mpls ldp graceful-restart timers max-recovery

•

mpls ldp graceful-restart timers neighbor-liveness

•

show mpls ip binding

•

show mpls ldp bindings

•

show mpls ldp gracefulrestart

•

show mpls ldp neighbor

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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Cisco Release 12.4 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

C O N T E N T S

MPLS Label Distribution Protocol (LDP)

Finding Feature Information

Prerequisites for MPLS LDP

Information About MPLS LDP

Introduction to MPLS LDP

MPLS LDP Functional Overview

LDP and TDP Support

Introduction to LDP Sessions

Directly Connected MPLS LDP Sessions

Nondirectly Connected MPLS LDP Sessions

Introduction to LDP Label Bindings Label Spaces and LDP Identifiers

How to Configure MPLS LDP

Enabling Directly Connected LDP Sessions

Establishing Nondirectly Connected MPLS LDP Sessions

Saving Configurations MPLS Tag Switching Commands

Specifying the LDP Router ID

Preserving QoS Settings with MPLS LDP Explicit Null

Protecting Data Between LDP Peers with MD5 Authentication

MPLS LDP Configuration Examples

Configuring Directly Connected MPLS LDP Sessions Example

Establishing Nondirectly Connected MPLS LDP Sessions Example

Additional References

Feature Information for MPLS Label Distribution Protocol

MPLS LDP Session Protection

Finding Feature Information

Restrictions for MPLS LDP Session Protection

Information About MPLS LDP Session Protection

MPLS LDP Session Protection Customizations

How to Configure MPLS LDP Session Protection

Enabling MPLS LDP Session Protection

Verifying MPLS LDP Session Protection

Troubleshooting Tips

Configuration Examples for MPLS LDP Session Protection

Additional References

Command Reference

MPLS LDP Inbound Label Binding Filtering

Finding Feature Information

Restrictions

Information about MPLS LDP Inbound Label Binding Filtering

How to Configure MPLS LDP Inbound Label Binding Filtering

Configuring MPLS LDP Inbound Label Binding Filtering

Verifying that MPLS LDP Inbound Label Bindings are Filtered

Configuration Examples for MPLS LDP Inbound Label Binding Filtering

Additional References

Feature Information for MPLS LDP Inbound Label Binding Filtering Feature

Glossary

MPLS LDP Autoconfiguration

Finding Feature Information

Restrictions for MPLS LDP Autoconfiguration

MPLS LDP Autoconfiguration on OSPF and IS-IS Interfaces

Information About MPLS LDP Autoconfiguration

How to Configure MPLS LDP Autoconfiguration

Configuring MPLS LDP Autoconfiguration with OSPF Interfaces

Disabling MPLS LDP Autoconfiguration from Selected OSPF Interfaces

Verifying MPLS LDP Autoconfiguration with OSPF

Configuring MPLS LDP Autoconfiguration with IS-IS Interfaces

Disabling MPLS LDP Autoconfiguration from Selected IS-IS Interfaces

Verifying MPLS LDP Autoconfiguration with IS-IS

Troubleshooting Tips

Configuration Examples for MPLS LDP Autoconfiguration

MPLS LDP Autoconfiguration with OSPF Example

MPLS LDP Autoconfiguration with IS-IS Examples

Additional References

Feature Information for MPLS LDP Autoconfiguration

MPLS LDP Graceful Restart

Finding Feature Information

Restrictions

How MPLS LDP Graceful Restart Works

Information About MPLS LDP Graceful Restart

How a Route Processor Advertises That It Supports MPLS LDP Graceful Restart

What Happens If a Route Processor Does Not Have LDP Graceful Restart

How to Configure MPLS LDP Graceful Restart

Configuring MPLS LDP Graceful Restart

Verifying the Configuration

Configuration Example for MPLS LDP Graceful Restart