MPLS High Availability: Overview
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MPLS High Availability: Overview

Table Of Contents

MPLS High Availability: Overview

Contents

Restrictions for MPLS High Availability

Information About MPLS High Availability

MPLS High Availability Overview

MPLS High Availability Features

NSF/SSO—MPLS VPN

NSF/SSO—MPLS LDP and LDP Graceful Restart

NSF/SSO: Any Transport over MPLS and Graceful Restart

MPLS High Availability Infrastructure Changes

Cisco Express Forwarding Scalability Enhancements

MPLS Applications That Coexist with SSO

MPLS Traffic Engineering

MPLS Quality of Service Applications

IPv6 over MPLS

MPLS Label Switching Router MIB

MPLS TE MIB

MPLS Enhancements to Interfaces MIB

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for MPLS High Availability: Overview


MPLS High Availability: Overview


First Published: August 11, 2004
Last Updated: August 21, 2007

This document provides an overview of the Multiprotocol Label Switching (MPLS) high availability (HA) features. MPLS HA provides full nonstop forwarding (NSF) and stateful switchover (SSO) capability to the MPLS Label Distribution Protocol (LDP) and MPLS Virtual Private Networks (VPNs) features.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for MPLS High Availability: Overview" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

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

Restrictions for MPLS High Availability

Information About MPLS High Availability

Additional References

Feature Information for MPLS High Availability: Overview

Restrictions for MPLS High Availability

For information about supported hardware, see the following documents:

For Cisco IOS Release 12.2(25)S, see the Cross-Platform Release Notes for Cisco IOS Release 12.2S.

For Cisco IOS Release 12.2SB, see the Cross-Platform Release Notes for Cisco IOS Release 12.2SB.

For Cisco IOS Release 12.2(33)SRA, see the Release Notes for Cisco IOS Release 12.2SR for the Cisco 7600 Series Routers

For Cisco IOS Release 12.2(33)SXH, see the Release Notes for Cisco IOS Release 12.2SX on the Catalyst 6500 Series MSFC

Information About MPLS High Availability

This section covers the following topics:

MPLS High Availability Overview

MPLS High Availability Features

MPLS High Availability Infrastructure Changes

MPLS Applications That Coexist with SSO

MPLS High Availability Overview

MPLS HA features provide SSO and NSF capability to the MPLS Label Distribution Protocol (LDP) and MPLS Virtual Private Network (VPN) features. MPLS HA includes the following new features:

NSF/SSO—MPLS VPN

NSF/SSO—MPLS LDP and LDP Graceful Restart

NSF/SSO: Any Transport over MPLS and Graceful Restart

In addition, the MIBs for MPLS VPNs and MPLS LDP have been enhanced to work in the MPLS HA environment.

The following features have been changed or created to work in the MPLS HA environment:

MPLS High Availability Infrastructure Changes

Cisco Express Forwarding Scalability Enhancements

The following features perform normally in an NSF/SSO environment. They can exist with SSO and NSF but do not have the ability to keep duplicate information in a backup Route Processor (RP) on the Cisco 7500 series router and in a backup Performance Routing Engine2 (PRE2) on the Cisco 10000 series router.

MPLS Traffic Engineering

MPLS Quality of Service Applications

IPv6 over MPLS (not supported on the Cisco 10000 series router)

MPLS Label Switching Router MIB

MPLS TE MIB

MPLS Enhancements to Interfaces MIB

The following sections explain these features in more detail.

MPLS High Availability Features

The following MPLS HA features have the ability to continue forwarding data following an RP switchover on the Cisco 7500 series router or PRE2 switchover on the Cisco 10000 series router:

MPLS Label Distribution Protocol (LDP)

MPLS Virtual Private Networks (VPNs)

Any Transport over MPLS (AToM)


Note In Cisco IOS Release 12.2(28)SB, AToM is not enabled for high availability on the Cisco 10000 series router. However, AToM coexists with SSO. This means that AToM functions normally in an SSO environment but because state information is not maintained on the standby RP, a switchover can partially disrupt operations


When you enable MPLS HA, you get the benefit of allowing an RP on the Cisco 7500 series router or PRE2 on the Cisco 10000 series router to recover from disruption in service without losing its LDP bindings, MPLS forwarding state, and VPN prefix information.

NSF/SSO—MPLS VPN

The NSF/SSO—MPLS VPN feature allows a router to recover from a disruption in service without losing its VPN prefix information. The NSF/SSO—MPLS VPN feature works with the BGP Graceful Restart mechanisms defined in the Graceful Restart Internet Engineering Task Force (IETF) specifications and in the Cisco Nonstop Forwarding feature module. The BGP Graceful Restart feature supports the VPNv4 VRFs, which allows the routers running BGP Graceful Restart to preserve VPN prefix information when a router restarts.

For information about configuring the NSF/SSO—MPLS VPN feature, see the following feature module: NSF/SSO—MPLS VPN.

NSF/SSO: MPLS VPN MIB

The NSF/SSO—MPLS VPN feature works with the MPLS VPN MIB. For information about configuring the MPLS VPN MIB, see the following feature module: MPLS VPN: SNMP MIB Support.

NSF/SSO—MPLS LDP and LDP Graceful Restart

MPLS LDP uses SSO, NSF, and Graceful Restart to allow an RP on the Cisco 7500 series router or PRE2 on the Cisco 10000 series router to recover from disruption in the LDP components of the control plane service without losing its MPLS forwarding state. The NSF/SSO—MPLS LDP and LDP Graceful Restart feature works with LDP sessions between directly connected peers as well as with peers that are not directly connected (targeted sessions).

For information about configuring the NSF/SSO—MPLS LDP and LDP Graceful Restart feature, see the following feature module: NSF/SSO—MPLS LDP and LDP Graceful Restart.

NSF/SSO: MPLS LDP MIB

The MPLS LDP MIB with the IETF Version 8 Upgrade is supported with NSF/SSO—MPLS LDP and LDP Graceful Restart. For information about configuring the MPLS LDP MIB, see the following feature module: MPLS Label Distribution Protocol MIB Version 8 Upgrade.

NSF/SSO: Any Transport over MPLS and Graceful Restart

AToM uses SSO, NSF, and Graceful Restart to allow an RP to recover from disruption in the LDP components of the control plane service without losing its MPLS forwarding state.


Note In Cisco IOS Release 12.2(28)SB, AToM is not enabled for high availability on the Cisco 10000 series router. However, AToM coexists with SSO. This means that AToM functions normally in an SSO environment but because state information is not maintained on the standby RP, a switchover can partially disrupt operations.


For information about configuring AToM NSF/SSO Support and Graceful Restart, see NSF/SSO: Any Transport over MPLS and Graceful Restart.

MPLS High Availability Infrastructure Changes

The MPLS control plane software has been enhanced to work in an HA environment. The changes made the control plane software more modular, which helps MPLS support newer applications. Some of the control plane software changes made MPLS more scalable and flexible. See the "Cisco Express Forwarding Scalability Enhancements" section for more information.

Changes to the MPLS Forwarding Infrastructure (MFI) and the Cisco Express Forwarding component introduced new commands and changed other existing commands.

MFI replaced the Label Forwarding Information Base (LFIB) and is responsible for managing MPLS data structures used for forwarding. For information about the MPLS command changes related to the MFI, see the following document: MPLS High Availability: Command Changes.


Note The MFI and LFIB do not coexist in the same image. Users must use MFI starting with Cisco IOS Release 12.2(25)S and later releases.


MPLS High Availability introduces the MPLS IP Rewrite Manager (IPRM), which manages the interactions between Cisco Express Forwarding, the IP Label Distribution Modules (LDMs), and the MFI. MPLS IPRM is enabled by default. You do not need to configure or customize the IPRM. See the "Feature Information for MPLS High Availability: Overview" section for show and debug commands related to IPRM.

Cisco Express Forwarding Scalability Enhancements

Cisco Express Forwarding provides a forwarding path and maintains a complete forwarding and adjacency table for both the software and hardware forwarding engines.

With MPLS High Availability, Cisco Express Forwarding supports new features and new hardware. The Cisco Express Forwarding improvements enable Cisco Express Forwarding to work with the MPLS HA applications and the MFI infrastructure. Cisco Express Forwarding improvements increase scalability, which are outlined in Table 1.

Table 1 Cisco Express Forwarding Scalability Enhancements 

For the Cisco 7500 Series Router
For the Cisco 10000 Series Router

Up to 512,000 prefixes

Up to 1 million prefixes

Up to 128,000 adjacencies

Up to 1 million adjacencies

4000 VPNs

4000 VPNs

Arbitrary prefix path counts from the Routing Information Base (RIB)

Arbitrary prefix path counts from the RIB

16 paths per prefix for forwarding

8 paths per prefix for forwarding

64 Cisco Express Forwarding instances (such as line cards or redundant RPs)

NA


Cisco Express Forwarding makes the following enhancements:

Improves memory use

Reduces large peak memory use

Reduces route convergence times for the Cisco 7500 series router.

For information about the Cisco Express Forwarding command changes, see Cisco Express Forwarding: Command Changes.

MPLS Applications That Coexist with SSO

The following sections list the MPLS features that maintain, either partially or completely, undisturbed operation through an RP switchover on the Cisco 7500 series router or PRE2 switchover on the Cisco 10000 series router.

MPLS Traffic Engineering

The MPLS Traffic Engineering (TE) features work with the new Cisco Express Forwarding and MFI modules. TE is SSO coexistent, which means it maintains, either partially or completely, undisturbed operation through an RP switchover on the Cisco 7500 series router or PRE2 switchover on the Cisco 10000 series router. No additional capabilities have been introduced with MPLS High Availability. The debug mpls traffic-eng lsd-client command is introduced with the MPLS High Availability features.

MPLS Quality of Service Applications

Cisco IOS MPLS supports the IETF DiffServ architecture by enabling the quality of service (QoS) functions listed in Table 2 to act on the MPLS packets.

Table 2 MPLS QoS Support 

Category
Related MPLS QoS Features

Traffic classification

Access Control List matching

Traffic marking

Differentiated services code point (DSCP)

MPLS Experimental (EXP) field

Congestion management

Low latency queueing (LLQ)

Class-based weighted fair queueing (CBWFQ)

Congestion avoidance

Weighted Random Early Detection (WRED)

Traffic conditioning

Shaping and policing


IPv6 over MPLS

The IPv6 over MPLS application works with the new Cisco Express Forwarding and MFI modules. IPv6 over MPLS is SSO coexistent, which means it maintains, either partially or completely, undisturbed operation through an RP switchover.


Note The Cisco 10000 series router does not support the IPv6 over MPLS application.


Command changes are documented in the Cisco IOS IPv6 Command Reference.

MPLS Label Switching Router MIB

The MPLS Label Switching Router (LSR) MIB works in the MPLS HA environment. Two indexes in the LSR MIB were changed to provide well-defined and ordered values:

mplsXCIndex

mplsOutSegmentIndex

This benefits the MPLS LSR MIB in the following ways:

The MIB walk-through has a consistent and logical order.

The same index values are maintained after a switchover.

For information about the MPLS LSR MIB, see the MPLS Label Switching Router MIB.

MPLS TE MIB

The MPLS TE MIB works in the MPLS HA environment. For information about the MPLS TE MIB, see the MPLS Traffic Engineering (TE) MIB.


Note After an RP switchover on the Cisco 7500 series router or PRE2 switchover on the Cisco 10000 series router, the value of mplsTunnelCreationTime in the TE MIB does not correctly reflect the time when the tunnel was created. After an RP or PRE2 switchover, the tunnel gets a new time stamp.


MPLS Enhancements to Interfaces MIB

The MPLS Enhancements to Interfaces MIB works in the MPLS HA environment. For information about the MPLS Enhancements to Interfaces MIB, see the MPLS Enhancements to Interfaces MIB.

Additional References

The following sections provide references related to the MPLS High Availability feature.

Related Documents


Standards

Standard
Title

draft-ietf-mpls-bgp-mpls-restart.txt

Graceful Restart Mechanism for BGP with MPLS

draft-ietf-mpls-idr-restart.txt

Graceful Restart Mechanism for BGP


MIBs

MIB
MIBs Link

MPLS VPN MIB

MPLS Label Distribution Protocol MIB Version 8 Upgrade

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

RFC 3478

Graceful Restart Mechanism for Label Distribution


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. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. If you have a valid service contract but do not have a user ID or password, you can register on Cisco.com.

http://www.cisco.com/techsupport


Feature Information for MPLS High Availability: Overview

Table 3 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.

Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.


Note Table 3 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 3 Feature Information for MPLS High Availability: Overview

Feature Name
Releases
Feature Information

MPLS High Availability: Overview

12.2(25)S
12.2(28)SB
12.2(33)SRA
12.2(33)SXH

This feature provides an overview of the Multiprotocol Label Switching (MPLS) high availability (HA) features.

In 12.2(25)S, this feature was introduced on the Cisco 7500 series router.

In 12.2(28)SB, support was added for the Cisco 10000.

In 12.2(33)SRA, support was added for the Cisco 7600 series routers.

In 12.2(33)SXH, this feature was integrated into Cisco IOS Release 12.2(33)SXH.