MPLS Traffic Engineering—Verbatim Path Support

First Published: August 26, 2003
Last Updated: May 4, 2009

The MPLS Traffic Engineering—Verbatim Path Support feature allows network nodes to support Resource Reservation Protocol (RSVP) extensions without supporting Interior Gateway Protocol (IGP) extensions for traffic engineering (TE), thereby bypassing the topology database verification process.

Finding Feature Information

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 for MPLS Traffic Engineering—Verbatim Path Support" section.

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

Contents

•Prerequisites for MPLS Traffic Engineering—Verbatim Path Support

•Restrictions for MPLS Traffic Engineering—Verbatim Path Support

•Information About MPLS Traffic Engineering—Verbatim Path Support

•How to Configure and Verify MPLS Traffic Engineering—Verbatim Path Support

•Configuration Example for MPLS Traffic Engineering—Verbatim Path Support

•Additional References

•Feature Information for MPLS Traffic Engineering—Verbatim Path Support

•Glossary

Prerequisites for MPLS Traffic Engineering—Verbatim Path Support

•A Multiprotocol Label Switching (MPLS) TE tunnel must be configured globally.

•MPLS TE must be enabled on all links.

Restrictions for MPLS Traffic Engineering—Verbatim Path Support

•The verbatim keyword can be used only on a label-switched path (LSP) that is configured with the explicit path option.

•This release does not support reoptimization on the verbatim LSP.

Information About MPLS Traffic Engineering—Verbatim Path Support

•MPLS TE Verbatim Path Support Overview

MPLS TE Verbatim Path Support Overview

MPLS TE LSPs usually require that all the nodes in the network are TE aware, meaning they have IGP extensions to TE in place. However, some network administrators want the ability to build TE LSPs to traverse nodes that do not support IGP extensions to TE, but that do support RSVP extensions to TE.

Verbatim LSPs are helpful when all or some of the intermediate nodes in a network do not support IGP extensions for TE.

When this feature is enabled, the IP explicit path is not checked against the TE topology database. Because the TE topology database is not verified, a Path message with IP explicit path information is routed using the shortest path first (SPF) algorithm for IP routing.

How to Configure and Verify MPLS Traffic Engineering—Verbatim Path Support

•Configuring MPLS Traffic Engineering—Verbatim Path Support (required)

•Verifying Verbatim LSPs for MPLS TE Tunnels (optional)

Configuring MPLS Traffic Engineering—Verbatim Path Support

SUMMARY STEPS

1. enable

2. configure terminal

3. interface tunnel number

4. ip unnumbered loopback number

5. tunnel destination {host-name | ip-address}

6. tunnel mode mpls traffic-eng

7. tunnel mpls traffic-eng bandwidth {sub-pool kbps | kbps}

8. tunnel mpls traffic-eng autoroute announce

9. tunnel mpls traffic-eng priority setup-priority [hold-priority]

10. tunnel mpls traffic-eng path-option preference-number {dynamic [attributes string | bandwidth {sub-pool kbps | kbps} | lockdown | verbatim] | explicit {name path-name | identifier path-number}}

11. exit

12. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

interface tunnel number

Example:

Router(config)# interface tunnel 1

Configures a tunnel interface and enters interface configuration mode.

•The number argument identifies the tunnel number to be configured.

Step 4  

ip unnumbered loopback number
Example: 
Router(config-if)# ip unnumbered loopback 1

Configures an unnumbered IP interface, which enables IP processing without an explicit address. A loopback interface is usually configured with the router ID.

Note An MPLS traffic engineering tunnel interface should be unnumbered because it represents a unidirectional link.

Step 5 

tunnel destination {host-name | ip-address}

Example:

Router(config-if)# tunnel destination 10.100.100.100

Specifies the destination for a tunnel.

•The host-name argument is the name of the host destination.

•The ip-address argument is the IP Version 4 address of the host destination expressed in decimal in four-part, dotted notation.

Step 6 

tunnel mode mpls traffic-eng

Example:

Router(config-if)# tunnel mode mpls traffic-eng

Sets the tunnel encapsulation mode to MPLS traffic engineering.

Step 7 

tunnel mpls traffic-eng bandwidth {sub-pool kbps | kbps}

Example: 
Router(config-if)# tunnel mpls traffic-eng 
bandwidth 1000

Configures the bandwidth required for an MPLS TE tunnel and assigns it either to the sub-pool or the global pool.

•The sub-pool keyword indicates a subpool tunnel.

•The kbps argument is the bandwidth, in kilobits per second, set aside for the MPLS TE tunnel. The range is from 1 to 4294967295.

Step 8 

tunnel mpls traffic-eng autoroute announce

Example:

Router(config-if)# tunnel mpls traffic-eng autoroute announce

Specifies that IGP should use the tunnel (if the tunnel is up) in its enhanced SPF calculation.

Step 9 

tunnel mpls traffic-eng priority setup-priority [hold-priority]

Example:

Router(config-if)# tunnel mpls traffic-eng priority 1 1

Configures setup and reservation priority for a tunnel.

•The setup-priority argument is the priority used when signaling an LSP for this tunnel to determine which existing tunnels can be preempted.

Valid values are from 0 to 7. A lower number indicates a higher priority. An LSP with a setup priority of 0 can preempt any LSP with a non-0 priority.

•The hold-priority argument is the priority associated with an LSP for this tunnel to determine if it should be preempted by other LSPs that are being signaled.

Valid values are from 0 to 7, where a lower number indicates a higher priority.

Step 10 

tunnel mpls traffic-eng path-option preference-number {dynamic [attributes string | bandwidth {sub-pool kbps | kbps} | lockdown | verbatim] | explicit {name path-name | identifier path-number}}

Example: 
Router(config-if)# tunnel mpls traffic-eng 
path-option 1 explicit name test verbatim

Specifies LSP-related parameters, including the verbatim keyword used with an explicit path option, for an MPLS TE tunnel.

•The preference-number argument identifies the path option.

•The protect keyword and preference-number argument identify the path option with protection.

•The dynamic keyword indicates that the path option is dynamically calculated. (The router figures out the best path.)

•The explicit keyword indicates that the path option is specified. The IP addresses are specified for the path.

•The name path-name keyword argument combination identifies the name of the explicit path option.

•The path-number argument identifies the number of the explicit path option.

•The verbatim keyword bypasses the topology database verification.

Note You can use the verbatim keyword only with the explicit path option.

•The attributes string keyword argument combination names an attribute list to specify path options for the LSP.

•The bandwidth keyword specifies the LSP bandwidth.

•The sub-pool keyword indicates a subpool path option.

•The kbps argument is the number of kilobits per second set aside for the path option. The range is from 1 to 4294967295.

•The lockdown keyword disables reoptimization of the LSP.

Step 11 

exit

Example:

Router(config-if)# exit

Exits interface configuration mode and returns to global configuration mode.

Step 12 

exit

Example:

Router(config)# exit

Exits global configuration mode and returns to privileged EXEC mode.

Verifying Verbatim LSPs for MPLS TE Tunnels

SUMMARY STEPS

1. enable

2. show mpls traffic-eng tunnels tunnel-interface [brief]

3. disable

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

show mpls traffic-eng tunnels tunnel-interface [brief]

Example:

Router# show mpls traffic-eng tunnels tunnel1

Displays information about tunnels including those configured with an explicit path option using verbatim.

Step 3 

disable

Example:

Router# disable

(Optional) Exits to user EXEC mode.

Configuration Example for MPLS Traffic Engineering—Verbatim Path Support

This section provides the following configuration example:

•Configuring MPLS Traffic Engineering—Verbatim Path Support: Example

Configuring MPLS Traffic Engineering—Verbatim Path Support: Example

The following example shows a tunnel that has been configured with an explicit path option using verbatim: 

interface tunnel 1

 ip unnumbered loopback 1

 tunnel destination 10.10.100.100

 tunnel mode mpls traffic-eng

 tunnel mpls traffic-eng bandwidth 1000

 tunnel mpls traffic-eng autoroute announce

 tunnel mpls traffic-eng priority 1 1

 tunnel mpls traffic-eng path-option 1 explicit name path1 verbatim

Additional References

Related Documents

Related Topic
Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

MPLS commands

Cisco IOS Multiprotocol Label Switching Command Reference

Interface commands

Cisco IOS Interface and Hardware Component Command Reference


Standards

Standard
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

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


RFCs

RFC
Title

No new or modified RFCs are supported by this release.

—


Technical Assistance

Description
Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html


Feature Information for MPLS Traffic Engineering—Verbatim Path Support

Table 1 lists the features in this module and provides links to specific configuration information.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.

Table 1 Feature Information for MPLS Traffic Engineering—Verbatim Path Support 

Feature Name
Releases
Feature Information

MPLS Traffic Engineering—Verbatim Path Support

Cisco IOS XE Release 2.3

The MPLS Traffic Engineering—Verbatim Path Support feature allows network nodes to support Resource Reservation Protocol (RSVP) extensions without supporting Interior Gateway Protocol (IGP) extensions for traffic engineering (TE), thereby bypassing the topology database verification process.

This feature was integrated into Cisco IOS XE Release 2.3.

The following sections provide information about this feature:

•Configuring MPLS Traffic Engineering—Verbatim Path Support

•Verifying Verbatim LSPs for MPLS TE Tunnels

The following commands were introduced or modified: show mpls traffic-eng tunnels, tunnel mpls traffic-eng path option.


Glossary

Fast Reroute—Procedures that enable temporary routing around a failed link or node while a new label-switched path (LSP) is being established at the head end.

headend—The router that originates and maintains a given label-switched path (LSP). This is the first router in the LSP's path.

IGP—Interior Gateway Protocol. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Routing Information protocol (RIP).

LSP—label-switched path. A configured connection between two routers, in which label switching is used to carry the packets. The purpose of an LSP is to carry data packets.

LSR—label switching router. A device that forwards Multiprotocol Label Switching (MPLS) packets based on the value of a fixed-length label encapsulated in each packet.

merge point—The backup tunnel's tail.

MPLS—Multiprotocol Label Switching. A method for forwarding packets (frames) through a network. It enables routers at the edge of a network to apply labels to packets (frames). ATM switches or existing routers in the network core can switch packets according to the labels with minimal lookup overhead.

PLR—point of local repair. The head-end of the backup tunnel.

RSVP—Resource Reservation Protocol. A protocol that supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive.

SPF—shortest path first. Routing algorithm that iterates on length of path to determine a shortest-path spanning tree. Commonly used in link-state routing algorithms. Sometimes called Dijkstra's algorithm.

tailend—The router upon which an label-switched path (LSP) is terminated. This is the last router in the LSP's path.

traffic engineering—The techniques and processes used to cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods had been used.

tunnel—A secure communications path between two peers, such as routers.

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

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