MPLS LDP-VRF-Aware Static Labels

Last Updated: November 29, 2011

This document explains how to configure the MPLS LDP--VRF-Aware Static Labels feature and Multiprotocol Label Switching (MPLS) static labels. Virtual Private Network routing and forwarding (VRF)-aware static labels can be used at the edge of an MPLS Virtual Private Network (VPN), whereas MPLS static labels can be used only in the MPLS VPN provider core.

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.

Information About MPLS LDP-VRF-Aware Static Labels

Overview of MPLS Static Labels and MPLS LDP--VRF-Aware Static Labels

Label switch routers (LSRs) dynamically learn the labels they should use to label-switch packets by means of the following label distribution protocols:

  • 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 MPLS VPNs

The LSR installs the dynamically learned label into its Label Forwarding Information Base (LFIB).

You can configure static labels for the following purposes:

  • To bind labels to IPv4 prefixes to support MPLS hop-by-hop forwarding through neighbor routers that do not implement LDP label distribution. MPLS static labels allow you to configure entries in the MPLS forwarding table and assign label values to forwarding equivalence classes (FECs) learned by LDP. You can manually configure an LSP without running an LDP between the endpoints.
  • To create static cross connects to support MPLS label switched path (LSP) midpoints when neighbor routers do not implement the LDP or RSVP label distribution, but do implement an MPLS forwarding path.
  • To statically bind a VRF-aware label on a provider edge (PE) router to a customer network prefix (VPN IPv4 prefix). VRF-aware static labels can be used with nonglobal VRF tables, so the labels can be used at the VPN edge. For example, with the Carrier Supporting Carrier (CSC) feature, the backbone carrier can assign specific labels to FECs it advertises to the edge routers of customer carriers. Then, backbone carrier can monitor backbone traffic coming from particular customer carriers for billing or other purposes. Depending on how you configure VRF-aware static labels, they are advertised one of the following ways:
    • By LDP between PE and customer edge (CE) routers within a VRF instance
    • In VPNv4 BGP in the service provider's backbone

Labels Reserved for Static Assignment

Before you can manually assign labels, you must reserve a range of labels to be used for the manual assignment. Reserving the labels ensures that the labels are not dynamically assigned.

How to Configure MPLS LDP--VRF-Aware Static Labels

Reserving Labels to Use for MPLS Static Labels and MPLS LDP--VRF-Aware Static Labels

To reserve the labels that are to be statically assigned so that the labels are not dynamically assigned, perform the following task.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    mpls label range minimum-value maximum-value [static minimum-static-value maximum-static-value]

4.    exit

5.    show mpls label range


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
mpls label range minimum-value maximum-value [static minimum-static-value maximum-static-value]


Example:

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

 

Reserves a range of labels for static labels assignment. The default is that no labels are reserved for static assignment.

Note    You might need to reload the router for the range of labels you reserve to take effect.
 
Step 4
exit


Example:

Router(config)# exit

 

Exits global configuration mode.

 
Step 5
show mpls label range


Example:

Router# show mpls label range

 

Displays information about the range of values for local labels, including those available for static assignment.

 

Configuring MPLS Static Labels in the MPLS VPN Provider Core

To configure MPLS static labels in the MPLS VPN provider core, perform the following task.

MPLS static labels allow you to configure entries in the MPLS forwarding table and assign label values to FECs learned by LDP. You can manually configure an LSP without running a label distribution protocol between the endpoints. In MPLS VPN networks, static labels can be used only in the MPLS VPN provider core.

Before You Begin
  • Globally enable MPLS on each LSR.
  • Enable Cisco Express Forwarding on each LSR.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    mpls static binding ipv4 prefix mask {label | input label | output nexthop {explicit-null | implicit-null | label}}

4.    exit

5.    show mpls static binding ipv4

6.    show mpls forwarding-table


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 and returns to privileged EXEC mode.

 
Step 3
mpls static binding ipv4 prefix mask {label | input label | output nexthop {explicit-null | implicit-null | label}}


Example:

Router(config)# mpls static binding ipv4 10.2.2.0 255.255.255.255 input 17

 

Specifies static binding of labels to IPv4 prefixes.

Specified bindings are installed automatically in the MPLS forwarding table as routing demands.

 
Step 4
exit


Example:

Router(config)# exit

 

Exits global configuration mode and enters privileged EXEC mode.

 
Step 5
show mpls static binding ipv4

Example:

Router# show mpls static binding ipv4

 

Displays the configured static labels.

 
Step 6
show mpls forwarding-table

Example:

Router# show mpls forwarding-table

 

Displays the static labels used for MPLS forwarding.

 

Configuring MPLS LDP--VRF-Aware Static Labels at the Edge of the VPN

To configure the MPLS LDP--VRF-Aware Static Labels feature at the edge of the VPN, perform the following task.

You can statically bind a VRF-aware label on a PE router to a customer network prefix (VPN IPv4 prefix). VRF-aware static labels can be used with nonglobal VRF tables, so the labels can be used at the VPN edge.

Restrictions

Before You Begin
  • Globally enable MPLS on each LSR.
  • Enable Cisco Express Forwarding on each LSR.
  • Ensure the MPLS VPN is configured.
  • Ensure that the provider network has MPLS LDP installed and running.

Note
The MPLS LDP-VRF-Aware Static Labels feature is supported only with MPLS VPN Carrier Supporting Carrier networks that use MPLS LDP.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    mpls static binding ipv4 vrf vpn-name prefix mask {input label| label }

4.    exit

5.    show mpls static binding ipv4 vrf vpn-name


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
mpls static binding ipv4 vrf vpn-name prefix mask {input label| label }


Example:

Router(config)# mpls static binding ipv4 vrf vpn100 10.2.0.0 255.255.0.0 input 17

 

Binds a prefix to a local label.

Specified bindings are installed automatically in the MPLS forwarding table as routing demands.

Note    You must configure the MPLS VPN and VRFs before creating VRF-aware static labels.
 
Step 4
exit


Example:

Router(config)# exit

 

Exits global configuration mode and enters privileged EXEC mode.

 
Step 5
show mpls static binding ipv4 vrf vpn-name


Example:

Router(config)# show mpls static binding ipv4 vrf vpn100

 

Displays the configured MPLS static bindings.

 

Troubleshooting Tips

To display information related to static binding events, use the debug mpls static binding vrf command.

Configuration Examples for MPLS LDP--VRF-Aware Static Labels

Example Reserving Labels to Use for MPLS Static Labels and MPLS LDP--VRF-Aware Static Labels

In the following example, the mpls label range command reserves a generic range of labels from 200 to 100000 and configures a static label range of 16 to 199: 

Router(config)# mpls label range 200 100000 static 16 199
% Label range changes take effect at the next reload.

In this example, the output from the show mpls label range command indicates that the new label ranges do not take effect until a reload occurs: 

Router# show mpls label range
 
Downstream label pool: Min/Max label: 16/100000
   [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: 

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

Example Configuring MPLS Static Labels in the MPLS VPN Provider Core

The following example configures input and output labels for several prefixes:

Router(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 55
Router(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 output 10.0.0.66 167
Router(config)# mpls static binding ipv4 10.66.0.0 255.255.0.0 input 17
 
Router(config)# mpls static binding ipv4 10.66.0.0 255.255.0.0 output 10.13.0.8 explicit-null

The show mpls static binding ipv4command displays the configured static labels:

Router# show mpls static binding ipv4
 
10.0.0.0/8: Incoming label: 55 
  Outgoing labels:
      10.0.0.66   167
10.66.0.0/24: Incoming label: 17
  Outgoing labels:
     10.13.0.8  explicit-null

Example Configuring MPLS LDP--VRF-Aware Static Labels at the VPN Edge

In the following example, the mpls static binding ipv4 vrf commands configure static label bindings. They also configure input (local) labels for various prefixes. 

Router(config)# mpls static binding ipv4 vrf vpn100 10.0.0.0 10.0.0.0 55
Router(config)# mpls static binding ipv4 vrf vpn100 10.66.0.0 255.255.0.0 input 17

In the following output, the show mpls static binding ipv4 vrfcommand displays the configured VRF-aware static bindings: 

Router# show mpls static binding ipv4 vrf
 vpn100 
10.0.0.0/8:   (vrf: vpn100)  Incoming label: 55
  Outgoing labels:  None
10.66.0.0/16:   (vrf: vpn100)  Incoming label: 17
  Outgoing labels:  None

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

MPLS VPN configuration information

Configuring MPLS Layer 3 VPNs

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 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 Information for MPLS LDP-VRF-Aware Static Labels

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.

Table 1 Feature Information for MPLS LDP-VRF-Aware Static Labels

Feature Name

Releases

Feature Information

MPLS LDP-VRF-Aware Static Labels

Cisco IOS XE Release 2.1

The MPLS LDP-VRF-Aware Static Labels feature explains how to configure the MPLS LDP-VRF-Aware Static Labels feature and MPLS static labels. VRF-aware static labels can be used at the edge of an MPLS VPN, whereas MPLS static labels can be used only in the MPLS VPN provider core.

In Cisco IOS XE Release 2.2, this feature was implemented on the Cisco ASR 1000 Series Aggregation Services Routers.

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

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