MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

First Published: January 16, 2003
Last Updated: February 27, 2009

The MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion feature provides a means to exclude a link or node from the path for Multiprotocol Label Switching (MPLS) TE label switched path (LSP).

The feature is enabled through the ip explicit-path command that allows you to create an IP explicit path and enter a configuration submode for specifying the path. The feature adds to the submode commands the exclude-address command for specifying addresses to exclude from the path.

If the excluded address for an MPLS TE LSP identifies a flooded link, the constraint-based shortest path first (CSPF) routing algorithm does not consider that link when computing paths for the LSP. If the excluded address specifies a flooded MPLS TE router ID, the CSPF routing algorithm does not allow paths for the LSP to traverse the node identified by the router ID.

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 (TE)—IP Explicit Address Exclusion" 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 (TE)—IP Explicit Address Exclusion

•Restrictions for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•Information About MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•How to Configure MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•Configuration Examples for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•Additional References

•Feature Information for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

Prerequisites for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

Your network must support the following Cisco IOS features in order to support IP explicit address exclusion:

•MPLS

•IP Cisco Express Forwarding

•Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF)

Restrictions for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

MPLS TE will accept an IP explicit path comprised of either all excluded addresses configured by the exclude-address command or all included addresses configured by the next-address command, but not a combination of both.

Information About MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•MPLS Traffic Engineering

•Cisco Express Forwarding

MPLS Traffic Engineering

MPLS is an Internet Engineering Task Force (IETF)-specified framework that provides for the efficient designation, routing, forwarding, and switching of traffic flows through the network.

Traffic engineering (TE) is the process of adjusting bandwidth allocations to ensure that enough is left for high-priority traffic.

In MPLS TE, the upstream router creates a network tunnel for a particular traffic stream, then fixes the bandwidth available for that tunnel.

Cisco Express Forwarding

Cisco Express Forwarding is an advanced, Layer 3 switching technology inside a router. It defines the fastest method by which a Cisco router forwards packets from ingress to egress interfaces. The ip cef command enables Cisco Express Forwarding globally, and the ip route-cache cef command enables Cisco Express Forwarding on an interface.

How to Configure MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•Configuring IP Explicit Address Exclusion (required)

•Configuring an MPLS Traffic Engineering Tunnel (required)

Configuring IP Explicit Address Exclusion

SUMMARY STEPS

1. enable

2. configure terminal

3. ip explicit-path {name path-name | identifier number} [enable | disable]

4. exclude-address ip-address

5. exit

6. show ip explicit-path

DETAILED STEPS

 
Command
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 

ip explicit-path {name path-name | identifier number} [enable | disable]

Example:

Router(config)# ip explicit-path name OmitR12

Specifies the name or number of the explicit path, and enables the path, and enters explicit-path configuration mode.

Step 4 

exclude-address ip-address

Example:

Router(cfg-ip-expl-path)# exclude-address 10.12.12.12

Excludes the specified link or node from consideration by the constraint-based SPF.

•The ip-address is a link address or the router ID for a node.

Step 5 

exit

Example:

Router(cfg-ip-expl-path)# exit

Exits from explicit-path configuration mode, and returns to global configuration mode.

Step 6 

show ip explicit-path

Example:

Router# show ip explicit-path

Displays information about configured IP explicit paths.

Configuring an MPLS Traffic Engineering Tunnel

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. ip unnumbered loopback0

5. tunnel destination ip-address

6. tunnel mode mpls traffic-eng

7. tunnel mpls traffic-eng bandwidth bandwidth

8. tunnel mpls traffic-eng path-option number {dynamic | explicit {name path-name | ID path-number}} [lockdown]

9. exit

10. show mpls traffic eng tunnels

DETAILED STEPS

 
Command
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 type number

Example:

Router(config)# interface tunnel11

Configures an interface type and enters interface configuration mode.

Step 4 

ip unnumbered loopback0

Example:

Router(config-if)# ip unnumbered loopback0

Assigns the tunnel interface an IP address.

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

Step 5 

tunnel destination ip-address

Example:

Router(config-if)# tunnel destination 10.11.11.11

Specifies the destination for a tunnel.

•The destination of the tunnel must be the MPLS traffic engineering router ID of the destination device.

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 bandwidth

Example:

Router(config-if)# tunnel mpls traffic-eng bandwidth 100

Configures the bandwidth for the MPLS traffic engineering tunnel.

Step 8 

tunnel mpls traffic-eng path-option number {dynamic | explicit {name path-name | ID path-number}} [lockdown]

Example: 
Router(config-if)# tunnel mpls traffic-eng path-option 2 dynamic

Configures the tunnel to use a named IP explicit path or a path dynamically calculated from the traffic engineering topology database.

•A dynamic path is used if an explicit path is unavailable.

Note To configure a path option that specifies an exclude address, specify the explicit keyword (not the dynamic keyword) and specify an IP explicit path configured according to the steps in the "Configuring IP Explicit Address Exclusion" section.

Step 9 

exit

Example:

Router(config-if)# exit

Exits from interface configuration mode.

Step 10 

show mpls traffic eng tunnels

Example:

Router# show mpls traffic eng tunnels

Shows information about tunnels, including the current tunnel path if a tunnel is operational.

•By viewing the command output, you can determine the path that was used to build a tunnel. If you entered the exclude-address command, the specified link or node should not be listed.

Configuration Examples for MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

•Configuring IP Explicit Address Exclusion: Example

•Configuring an MPLS Traffic Engineering Tunnel: Example

Configuring IP Explicit Address Exclusion: Example

The following example shows how to configure an MPLS TE tunnel with two path options: a preferred explicit path with an excluded address and a backup dynamic path.

Configure the IP explicit path named OmitR12, which excludes the router with router ID 10.12.12.12: 

ip explicit-path name OmitR12 

exclude-address 10.12.12.12 

   Explicit Path name OmitR12: 

   1: exclude-address 10.12.12.12 

exit

To verify the configuration of the explicit path, use the show ip explicit-path command. 

show ip explicit-paths name OmitR12 

PATH OmitR12 (loose source route, path complete, generation 3)

 1: exclude-address 10.12.12.12

Note You must know the router IDs for LSRs (nodes) in the network; in this example, that 10.12.12.12 is a router ID. Otherwise, it will not be apparent whether the specified address is the IP address of a link or a router ID.

Configuring an MPLS Traffic Engineering Tunnel: Example

The following example configures Tunnel11 with its two options, where the preferred path option is the IP explicit path OmitR2: 

interface tunne l11

ip unnumbered loopback0

tunnel destination 10.11.11.11

tunnel mode mpls traffic-eng

tunnel mpls traffic-eng path-option 1 explicit name OmitR12

tunnel mpls traffic-eng path-option 2 dynamic

Note There are additional commands for configuring properties for TE tunnels such as bandwidth and priority. For descriptions of those commands, refer to the Cisco IOS IP Switching Services Configuration Guide.

Additional References

Related Documents

Related Topic
Document Title

MPLS commands

Cisco IOS Multiprotocol Label Switching 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.

—


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


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 (TE)—IP Explicit Address Exclusion

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 (TE)—IP Explicit Address Exclusion

Feature Name
Releases
Feature Configuration Information

MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion

12.0(14)ST
12.2(4)T
12.2(4)T2
12.2(14)S
12.0(32)S
12.2(28)SB

The MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion feature provides a means to exclude a link or node from the path for Multiprotocol Label Switching (MPLS) TE label switched path (LSP).

The following command was introduced by this feature: exclude-address.

In 12.0(14)ST, this feature was introduced.

In 12.2(4)T, this feature was integrated into Release 12.2(4)T.

In 12.2(4)T2, this feature was integrated into Release 12.2(4)T2.

In 12.2(14)S, this feature was integrated into Release 12.2(14)S.

In 12.0(32)S, this feature was integrated into Release 12.0(32)S.

In 12.2(28)SB, this feature was integrated into Release 12.2(28)SB.


Glossary

CEF—Cisco express forwarding. A means for accelerating the forwarding of packets within a router, by storing route lookup information in several data structures instead of in a route cache.

IP explicit path—A list of IP addresses, each representing a node or link in the explicit path.

link—Network communications channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Sometimes referred to as a line or a transmission link.

MPLS—Multiprotocol Label Switching. Switching method that forwards IP traffic using a label. This label instructs the routers and the switches in the network where to forward the packets based on preestablished IP routing information.

node—Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be interconnected by links, and serve as control points in the network.

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.

© 2003—2009 Cisco Systems, Inc. All rights reserved.