MPLS Traffic Engineering: Verbatim Path Support

First Published: August 26, 2003
Last Updated: February 27, 2008

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

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 for MPLS Traffic Engineering: Verbatim Path Support" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS 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

•Glossary

Prerequisites for MPLS Traffic Engineering: Verbatim Path Support

•An 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.

•You cannot configure MPLS Traffic Engineering over the logical GRE tunnel interface.

Information About MPLS Traffic Engineering: Verbatim Path Support

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

11. end

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

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}}

- or -

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

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

 
        
 
        
 
         
Router(config-if)# tunnel mpls traffic-eng 
path-option protect 2 dynamic name test 2 
bandwidth sub-pool 34

 
        
 
       
 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  
 		 
       
end 
 
        

          Example: 
        
 
Router(config)# end 
 
       
 (Optional) Exits 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. 
 		 
      
 
      
    
 
   
 
   
 
 
     
    
   
 Examples 
 
    
   
 In the following example, the show mpls traffic-eng tunnels command displays tunnel information, including whether the explicit path option is using verbatim and the Active Path Options Parameters that show the status of verbatim. 
 
    
   
Router# show mpls traffic-eng tunnels tunnel100 
 
    
   
 
    
 
   
 
    
   
 
    
Name: GSR-2_t100                          (Tunnel100) Destination: 192.168.30.1

 
   
 
    
   
 
    
  Status:

 
   
 
    
   
 
    
    Admin: up         Oper: up     Path: valid       Signalling: connected

 
   
 
    
   
 
    
 
   
 
    
   
 
    
    path option 1, type explicit (verbatim) BACKUP (Basis for Setup, path weight 0)

 
   
 
    
   
 
    
 
   
 
    
   
 
    
  Config Parameters:

 
   
 
    
   
 
    
    Bandwidth: 0        kbps (Global)  Priority: 7  7   Affinity: 0x0/0xFFFF

 
   
 
    
   
 
    
    Metric Type: TE (default)

 
   
 
    
   
 
    
    AutoRoute:  disabled  LockDown: disabled  Loadshare: 0        bw-based

 
   
 
    
   
 
    
    auto-bw: disabled

 
   
 
    
   
 
    
  Active Path Option Parameters:

 
   
 
    
   
 
    
    State: explicit path option 1 is active

 
   
 
    
   
 
    
    BandwidthOverride: disabled  LockDown: disabled  Verbatim: enabled 

 
   
 
     
    
    
   
 Configuration Example for MPLS Traffic Engineering: Verbatim Path Support 
 
    
   
 •Configuring MPLS Traffic Engineering: Verbatim Path Support 
 
     
    
    
   
 Configuring MPLS Traffic Engineering: Verbatim Path Support 
 
    
   
 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 
        
 		 
      
 
      
 
       
 MPLS Label Distribution Protocol 
 		 
       
 MPLS Label Distribution Protocol (LDP) feature module 
 		 
      
 
      
    
 
   
 
   
 
   
 
 
     
    
    
   
 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 IOS 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 website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. 
 
 To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. 
 
 Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. 
 		 
       
 http://www.cisco.com/techsupport  
 		 
      
 
      
    
 
   
 
   
 
   
  
 
     
    
    
    
   
 Feature Information for MPLS Traffic Engineering: Verbatim Path Support 
 
    
   
 Table 1 lists the release history for this feature. 
 
    
   
 Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation. 
 
    
   
 Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS 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 software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS 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 
 		 
       
 12.0(26)S
12.2(33)SRA
12.2(33)SXH
12.4(20)T 
 		 
       
 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. 
 
 In 12.0(26)S, this feature was introduced. 
 
 This feature was integrated into Cisco IOS Release 12.2(33)SRA. 
 
 This feature was integrated into Cisco IOS Release 12.2(33)SXH. 
 
 This feature was integrated into Cisco IOS Release 12.4(20)T. 
 
 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 LSP is being established at the head end.  
 
    
   
 headend—The router that originates and maintains a given 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 IGRP, OSPF, and 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 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 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. 
 
    
    
   
 Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at 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. (1005R) 
 
    
    
    
   
 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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