MPLS Static Labels
This document describes the Cisco MPLS Static Labels feature. The MPLS Static Labels feature provides the means to configure statically:
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.
Restrictions for MPLS Static Labels
- The trouble shooting process for MPLS static labels is complex.
- On a provider edge (PE) router for MPLS VPNs, there is no mechanism for statically binding a label to a customer network prefix (VPN IPv4 prefix).
- MPLS static crossconnect labels remain in the LFIB even if the router to which the entry points goes down.
- MPLS static crossconnect mappings remain in effect even with topology changes.
- MPLS static labels are not supported for label-controlled Asynchronous Transfer Mode (lc-atm).
- MPLS static bindings are not supported for local prefixes.
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
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 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 statically:
- The binding between a label and an IPv4 prefix
- The contents of an LFIB crossconnect entry
Benefits of MPLS Static Labels
Static Bindings Between Labels and IPv4 Prefixes
Static bindings between labels and IPv4 prefixes can be configured to support MPLS hop-by-hop forwarding through neighbor routers that do not implement LDP label distribution.
Static Crossconnects
Static crossconnects can be configured to support MPLS Label Switched Path (LSP) midpoints when neighbor routers do not implement either the LDP or RSVP label distribution, but do implement an MPLS forwarding path.
How to Configure MPLS Static Labels
- Configuring MPLS Static Prefix Label Bindings
- Verifying MPLS Static Prefix Label Bindings
- Configuring MPLS Static Crossconnects
- Verifying MPLS Static Crossconnect Configuration
- Monitoring and Maintaining 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:
DETAILED STEPS
Verifying MPLS Static Prefix Label Bindings
To verify the configuration for MPLS static prefix/label bindings, use this procedure:
DETAILED STEPS
| 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:
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
The following output from the show mpls label range command, executed after a reload, indicates that the new label ranges are in effect: Example:
Router# 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:
Router# 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:
Router# 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 |
Configuring MPLS Static Crossconnects
To configure MPLS static crossconnects, use the following command beginning in global configuration mode:
DETAILED STEPS
Verifying MPLS Static Crossconnect Configuration
To verify the configuration for MPLS static crossconnects, use this procedure:
DETAILED STEPS
|
Example:
Router# show mpls static crossconnect
Local Outgoing Outgoing Next Hop
label label interface
34 22 pos3/0/0 point2point (in LFIB)
|
Monitoring and Maintaining MPLS Static Labels
To monitor and maintain MPLS static labels, use one or more of the following commands:
DETAILED STEPS
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 from 16 to 100000 to 200 to 100000 and configures a static label range of 16 to 199.
Router# 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 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
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:
Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. 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 2607 Router(config)# mpls static binding ipv4 10.6.0.0 255.255.0.0 input 17 Router(config)# mpls static binding ipv4 10.0.0.0 255.0.0.0 output 10.13.0.8 explicit-null Router(config)# end
In the following output, the show mpls static binding ipv4 command displays the configured static prefix/label bindings:
Router# 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
Example Configuring MPLS Static Crossconnects
In the following output, the mpls static crossconnect command configures a crossconnect from incoming label 34 to outgoing label 22 out interface pos3/0/0:
Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# mpls static crossconnect 34 pos3/0/0 22 Router(config)# end
In the following output, the show mpls static crossconnect command displays the configured crossconnect:
Router# show mpls static crossconnect
Local Outgoing Outgoing Next Hop
label label interface
34 22 pos3/0/0 point2point (in LFIB)
Additional References
Related Documents
| Related Topic |
Document Title |
|---|---|
| Cisco IOS commands |
|
| MPLS commands |
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. |
-- |
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: |
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. |
-- |
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. |
Feature Information for MPLS 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 Static Labels |
Glossary
BGP --Border Gateway Protocol. The predominant interdomain routing protocol used in IP networks.
Border Gateway Protocol --See BGP.
FIB --Forwarding Information Base. A table that contains a copy of the forwarding information in the IP routing table.
Forwarding Information Base --See FIB.
label --A short, fixed-length identifier that tells switching nodes how the data (packets or cells) should be forwarded.
label binding --An association between a label and a set of packets, which can be advertised to neighbors so that a label switched path can be established.
Label Distribution Protocol --See LDP.
Label Forwarding Information Base --See LFIB.
label imposition --The act of putting the first label on a packet.
label switching router --See LSR.
LDP --Label Distribution Protocol. The protocol that supports MPLS hop-by-hop forwarding by distributing bindings between labels and network prefixes.
LFIB --Label Forwarding Information Base. A data structure in which destinations and incoming labels are associated with outgoing interfaces and labels.
LSR --label switching router. A Layer 3 router that forwards a packet based on the value of an identifier encapsulated in the packet.
MPLS --Multiprotocol Label Switching. An industry standard on which label switching is based.
MPLS hop-by-hop forwarding --The forwarding of packets along normally routed paths using MPLS forwarding mechanisms.
Multiprotocol Label Switching --See MPLS.
Resource Reservation Protocol --See RSVP.
RIB --Routing Information Base. A common database containing all the routing protocols running on a router.
Routing Information Base --See RIB.
RSVP --Resource Reservation Protocol. A protocol for reserving network resources to provide quality of service guarantees to application flows.
traffic engineering --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 were used.
Virtual Private Network --See VPN.
VPN --Virtual Private Network. A network that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.
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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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