Configuring MPLS Static Labels

MPLS Static Labels

This document describes the Cisco MPLS Static Labels feature. The MPLS Static Labels feature provides the means to configure the binding between a label and an IPv4 prefix statically.

Prerequisites for MPLS Static Labels

The network must support the following Cisco IOS features before you enable MPLS Static Labels:

  • Multiprotocol Label Switching (MPLS)

  • Cisco Express Forwarding

Restrictions for MPLS Static Labels

  • On a provider edge (PE) router for MPLS VPNs, there’s no mechanism for statically binding a label to a customer network prefix (VPN IPv4 prefix).

  • MPLS Static Crossconnect is not supported.

  • MPLS Static Labels is not supported for label-controlled Asynchronous Transfer Mode (lc-atm).

  • MPLS static bindings are not supported for local prefixes.

  • VRF aware Static Labels is not supported,

Information About MPLS Static Labels

MPLS Static Labels Overview

Generally, label switching routers (LSRs) dynamically learn the labels they should use to label-switch packets. They do this by means of label distribution protocols that include:

  • Label Distribution Protocol (LDP), the Internet Engineering Task Force (IETF) standard, used to bind labels to network addresses.

  • Resource Reservation Protocol (RSVP) used to distribute labels for traffic engineering (TE)

  • Border Gateway Protocol (BGP) used to distribute labels for Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs)

To use a learned label to label-switch packets, an LSR installs the label into its Label Forwarding Information Base (LFIB).

The MPLS Static Labels feature provides the means to configure the binding between a label and an IPv4 prefix statically.

Benefits of MPLS Static Labels

Static Bindings Between Labels and IPv4 Prefixes

You can configure static bindings between labels and IPv4 prefixes to support MPLS hop-by-hop forwarding through neighbor routers that don’t implement LDP label distribution.

How to Configure MPLS Static Labels

Configuring MPLS Static Prefix Label Bindings

To configure MPLS static prefix/label bindings, use the following commands beginning in global configuration mode:

Procedure
  Command or Action Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

mpls label range min-label max-label [static min-static-label max-static-label ]

Example:

Device(config)# mpls label range 200 100000 static 16 199

Specifies a range of labels for use with MPLS Static Labels feature.

(Default is no labels reserved for static assignment.)

Step 4

mpls static binding ipv4 prefix mask [input | output nexthop ] label

Example:

Device(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 55

Specifies static binding of labels to IPv4 prefixes.

Bindings specified are installed automatically in the MPLS forwarding table as routing demands.

Verifying MPLS Static Prefix Label Bindings

To verify the configuration for MPLS static prefix/label bindings, use this procedure:

Procedure

Step 1

Enter show mpls label range command. The output shows that the new label ranges do not take effect until a reload occurs:

Example:

Device# show mpls label range
 
Downstream label pool: Min/Max label: 16/983039
   [Configured range for next reload: Min/Max label: 200/100000]
Range for static labels: Min/Max/Number: 16/199

The following output from the show mpls label range command, executed after a reload, indicates that the new label ranges are in effect:

Example:

Device# show mpls label range
 
Downstream label pool: Min/Max label: 200/100000
Range for static labels: Min/Max/Number: 16/199

Step 2

Enter the show mpls static binding ipv4 command to show the configured static prefix/label bindings:

Example:

Device# show mpls static binding ipv4
10.17.17.17/32: Incoming label: 251 (in LIB)
  Outgoing labels:
     10.0.0.1                  18
10.18.18.18/32: Incoming label: 201 (in LIB)
  Outgoing labels: 
10.0.0.1	implicit-null

Step 3

Use the show mpls forwarding-table command to determine which static prefix/label bindings are currently in use for MPLS forwarding.

Example:

Device# show mpls forwarding-table
Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop    
tag    tag or VC   or Tunnel Id      switched   interface              
201    Pop tag     10.18.18.18/32    0          PO1/1/0    point2point  
       2/35        10.18.18.18/32    0          AT4/1/0.1  point2point  
251    18          10.17.17.17/32    0          PO1/1/0    point2point

Monitoring and Maintaining MPLS Static Labels

To monitor and maintain MPLS Static Labels, use one or more of the following commands:

Procedure
  Command or Action Purpose

Step 1

enable

Example:

Devie> enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

show mpls forwarding-table

Example:

Device# show mpls forwarding-table

Displays the contents of the MPLS LFIB.

Step 3

show mpls label range

Example:

Device# show mpls label range

Displays information about the static label range.

Step 4

show mpls static binding ipv4

Example:

Device# show mpls static binding ipv4

Displays information about the configured static prefix/label bindings.

Configuration Examples for MPLS Static Labels

Example: Configuring MPLS Static Prefixes Labels

In the following output, the mpls label range command reconfigures the range used for dynamically assigned labels 16–983039 to 200–100000. It configures a static label range of 16–199. 


Device# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# mpls label range 200 100000 static 16 199
% Label range changes take effect at the next reload.
Router(config)# end

In the following output, the show mpls label range command indicates that the new label ranges don’t take effect until a reload occurs: 


Device# show mpls label range
 
Downstream label pool: Min/Max label: 16/983039
   [Configured range for next reload: Min/Max label: 200/100000]
Range for static labels: Min/Max/Number: 16/199

In the following output, the show mpls label range command, executed after a reload, indicates that the new label ranges are in effect: 


Device# show mpls label range
 
Downstream label pool: Min/Max label: 200/100000
Range for static labels: Min/Max/Number: 16/199

In the following output, the mpls static binding ipv4 commands configure static prefix/label bindings. They also configure input (local) and output (remote) labels for various prefixes: 


Device# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Device(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 55
Device(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 output 10.0.0.66 2607
Device(config)# mpls static binding ipv4 10.6.0.0 255.255.0.0 input 17
Device(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 output 10.13.0.8 explicit-null
Device(config)# end

In the following output, the show mpls static binding ipv4 command displays the configured static prefix/label bindings: 


Device# show mpls static binding ipv4
 
10.0.0.0/8: Incoming label: none;
  Outgoing labels:
10.13.0.8           explicit-null
10.0.0.0/8: Incoming label: 55 (in LIB)
  Outgoing labels:
     10.0.0.66              2607
10.66.0.0/16: Incoming label: 17 (in LIB)
  Outgoing labels:  None

Additional References

Related Documents

Related Topic

Document Title

MPLS commands

Multiprotocol Label Switching Command Reference

Standards

Standard

Title

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

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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 feature, and support for existing RFCs has not been modified by this feature.

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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 History for MPLS Static Labels

This table provides release and related information for features explained in this module.

These features are available on all releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Gibraltar 16.11.1

MPLS Static Labels

The MPLS Static Labels feature provides the means to configure the binding between a label and an IPv4 prefix statically.

The following commands were introduced or modified: debug mpls static binding , mpls label range , mpls static binding ipv4 , show mpls label range , show mpls static binding ipv4

Use Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn.