Table Of Contents

NSF/SSO—Any Transport over MPLS and AToM Graceful Restart

Finding Feature Information

Contents

Prerequisites for AToM NSF

Supported Hardware

Neighbor Routers in the MPLS HA Environment

Stateful Switchover

Nonstop Forwarding for Routing Protocols

Restrictions for AToM NSF

Information About AToM NSF

How AToM NSF Works

AToM Information Checkpointing

Checkpointing Troubleshooting Tips

ISSU Support

Configuring MPLS LDP Graceful Restart

Configuration Examples for AToM NSF

Ethernet to VLAN Interworking with AToM NSF: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

Feature Information for AToM NSF

NSF/SSO—Any Transport over MPLS and AToM Graceful Restart

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First Published: August 11, 2004

Last Updated: February 27, 2009

The NSF/SSO—Any Transport over MPLS and AToM Graceful Restart feature allows Any Transport over MPLS (AToM) to use Cisco nonstop forwarding (NSF), stateful switchover (SSO), and Graceful Restart (GR) to allow a Route Processor (RP) to recover from a disruption in control plane service without losing its Multiprotocol Label Switching (MPLS) forwarding state.

NSF with SSO is effective at increasing availability of network services. Cisco NSF with SSO provides continuous packet forwarding, even during a network processor hardware or software failure. In a redundant system, the secondary processor recovers control plane service during a critical failure in the primary processor. SSO synchronizes the network state information between the primary and the secondary processor.

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Note In this document, the NSF/SSO—Any Transport over MPLS and AToM Graceful Restart feature is referred to as AToM NSF for brevity.

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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 AToM NSF" 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 AToM NSF

•Restrictions for AToM NSF

•Information About AToM NSF

•Configuration Examples for AToM NSF

•Additional References

•Command Reference

•Feature Information for AToM NSF

Prerequisites for AToM NSF

Before you can configure AToM NSF, make sure the following tasks have been completed:

•AToM virtual circuits (VCs) have been configured on the router. See the Any Transport over MPLS feature module for information on configuring AToM. For configuring L2VPN Interworking, see the L2VPN Interworking feature module.

•SSO has been configured on the Route Processors. See the Stateful Switchover feature module for configuration information.

•Nonstop forwarding has been configured on the routers. You must enable nonstop forwarding on the routing protocols running between the P routers, PE routers, and CE routers. The routing protocols are Open Shortest Path First (OSPF), Intermediate System-to-Intermediate System (IS-IS), and Border Gateway Protocol (BGP). See the Cisco Nonstop Forwarding feature module for configuration information.

This section lists the following prerequisites:

•Supported Hardware

•Neighbor Routers in the MPLS HA Environment

•Stateful Switchover

•Nonstop Forwarding for Routing Protocols

Supported Hardware

For hardware requirements for this feature, see the following documents:

•For Cisco IOS Release 12.2(25)S, see the "Supported Hardware" section of the Cross-Platform Release Notes for Cisco IOS Release 12.2S.

The URL is:
http://www.cisco.com/en/US/docs/ios/12_2s/release/notes/122Srn.html

•For Cisco IOS Release 12.2(28)SB, see the "Supported Hardware" section of the Cross-Platform Release Notes for Cisco IOS Release 12.2SB.

The URL is:
http://www.cisco.com/en/US/docs/ios/12_2sb/release/notes/122SB.html

•For Cisco IOS Release 12.2(33)SRC, see the "Supported Hardware" section of the Release Notes for Cisco IOS Release 12.2SR for the Cisco 7600 Series Routers.

The URL is:
http://www.cisco.com/en/US/docs/ios/12_2sr/release/notes/122SRrn.html

Neighbor Routers in the MPLS HA Environment

AToM NSF requires that neighbor networking devices be able to perform AToM GR. In Cisco IOS Releases 12.2(25)S and 12.2(28)SB, the Cisco 7200 and Cisco 7500 routers are capable of supporting AToM GR and can be used as neighbor networking devices.

In Cisco IOS Release 12.2(33)SRC, the Cisco 7600 routers are capable of supporting AToM high availability (HA) and MPLS Label Distribution Protocol (LDP) GR.

Stateful Switchover

To perform AToM NSF, Route Processors must be configured for SSO and GR. See the Stateful Switchover feature module for more information.

Nonstop Forwarding for Routing Protocols

You must enable NSF on the routing protocols running between the provider (P) routers, provider edge (PE) routers, and customer edge (CE) routers. The routing protocols are the following:

•Border Gateway Protocol (BGP)

•Open Shortest Path First (OSPF)

•Intermediate System-to-Intermediate System (IS-IS)

See the Cisco Nonstop Forwarding feature module for more information.

Restrictions for AToM NSF

AToM NSF includes the following restrictions:

•Tag Distribution Protocol (TDP) sessions are not supported. Only LDP sessions are supported.

•AToM NSF cannot be configured on label-controlled ATM (LC-ATM) interfaces.

•AToM NSF supports AToM Layer 2 Virtual Private Network (L2VPN) Interworking. However, Layer 2 Tunnel Protocol Version 3 (L2TPv3) Interworking is not supported.

•AToM NSF interoperates with Layer 2 local switching. However, AToM NSF has no effect on interfaces configured for local switching.

•To allow distributed Cisco Express Forwarding to work on the interfaces, disable fair queueing on serial interfaces.

•On the Cisco 7500 series routers, distributed Cisco Express Forwarding is needed to support AToM NSF.

•The Cisco 7500 router does not support AToM Ethernet-VLAN interworking IP; however, AToM Ethernet-VLAN interworking Ethernet is supported.

Information About AToM NSF

To configure AToM NSF, you should understand the following concepts:

•How AToM NSF Works

•AToM Information Checkpointing

•ISSU Support

How AToM NSF Works

AToM NSF improves the availability of a service provider's network that uses AToM to provide Layer 2 VPN services to its customers. HA provides the ability to detect failures and handle them with minimal disruption to the service being provided. AToM NSF is achieved by SSO and NSF mechanisms. A standby RP provides control-plane redundancy. The control plane state and data plane provisioning information for the attachment circuits (ACs) and AToM pseudowires (PWs) are checkpointed to the standby RP to provide NSF for AToM L2VPNs.

AToM Information Checkpointing

Checkpointing is a function that copies state information from the active RP to the backup RP, thereby ensuring that the backup RP has the latest information. If the active RP fails, the backup RP can take over.

For the AToM NSF feature, the checkpointing function copies the active RP's information bindings to the backup RP. The active RP sends updates to the backup RP when information is modified.

To display checkpointing data, issue the show acircuit checkpoint command on the active and backup RPs. The active and backup RPs have identical copies of the information.

Checkpointing Troubleshooting Tips

To help troubleshoot checkpointing errors, use the following commands:

•Use the debug acircuit checkpoint command to enable checkpointing debug messages for ACs.

•Use the debug mpls l2transport checkpoint command to enable checkpointing debug messages for AToM.

•Use the show acircuit checkpoint command to display the AC checkpoint information.

•Use the show mpls l2transport checkpoint command to display whether checkpointing is allowed, how many AToM VCs were bulk-synchronized (on the active RP), and how many AToM VCs have checkpoint data (on the standby RP).

•Use the show mpls l2transport vc detail command to display details of VC checkpointed information.

ISSU Support

Beginning with Cisco IOS Release 12.2(33)SRC, AToM NSF supports In Service Software Upgrade (ISSU) capability. Virtual Private LAN Services (VPLS) NSF/SSO and HA with ISSU work together to enable upgrades or downgrades of a Cisco IOS image without control and data plane outages. With ISSU, all message data structures that are used for checkpointing and exchanges between the active RP and standby RP are versioned.

Configuring MPLS LDP Graceful Restart

Before you configure AToM NSF, you need to configure MPLS LDP Graceful Restart.

MPLS LDP GR is enabled globally. When you enable LDP GR, it has no effect on existing LDP sessions. LDP GR is enabled for new sessions that are established after the feature has been globally enabled.

Perform this task to configure MPLS LDP GR.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip cef [distributed]

4. mpls ldp graceful-restart

5. interface type slot/port

6. mpls ip

7. mpls label protocol {ldp | tdp | both}

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	ip cef [distributed] Example: Router(config)# ip cef distributed	Enables Cisco Express Forwarding. Note In Cisco ASR 1000 series Aggregation Services Routers, the distributed keyword is mandatory.
Step 4	mpls ldp graceful-restart Example: Router (config)# mpls ldp graceful-restart	Enables the router to protect the LDP bindings and MPLS forwarding state during a disruption in service.
Step 5	interface type slot/port Example: Router(config)# interface pos 3/0	Specifies an interface and enters interface configuration mode.
Step 6	mpls ip Example: Router(config-if)# mpls ip	Configures MPLS hop-by-hop forwarding for an interface.
Step 7	mpls label protocol {ldp | tdp | both} Example: Router(config-if)# mpls label protocol ldp	Configures the use of LDP for an interface. •You must use LDP, because TDP sessions are not supported. •You can also issue the mpls label protocol ldp command in global configuration mode, which enables LDP on all interfaces configured for MPLS.

Configuration Examples for AToM NSF

This section provides the following configuration example:

•Ethernet to VLAN Interworking with AToM NSF: Example

Ethernet to VLAN Interworking with AToM NSF: Example

The following example shows how to configure AToM NSF on two PE routers:

PE1

PE2

ip cef distributed ! redundancy mode sso ! boot system flash disk2:rsp-pv-mz ! mpls ldp graceful-restart mpls ip mpls label protocol ldp mpls ldp router-id Loopback0 force mpls ldp advertise-labels ! pseudowire-class atom-eth  encapsulation mpls  interworking ethernet ! interface Loopback0  ip address 10.8.8.8 255.255.255.255 ! interface FastEthernet1/1/0  xconnect 10.9.9.9 123 encap mpls pw-class atom-eth interface POS6/1/0  ip address 10.1.1.1 255.255.255.0  mpls ip  mpls label protocol ldp  clock source internal  crc 32 ! interface Loopback0  ip address 10.8.8.8 255.255.255.255  no shutdown ! router ospf 10  nsf  network 10.8.8.8 0.0.0.0 area 0  network 19.1.1.1 0.0.0.0 area 0

ip cef distributed ! redundancy mode sso ! boot system flash disk2:rsp-pv-mz mpls ldp graceful-restart mpls ip mpls label protocol ldp mpls ldp router-id Loopback0 force mpls ldp advertise-labels ! pseudowire-class atom-eth  encapsulation mpls  interworking eth ! interface Loopback0  ip address 10.9.9.9 255.255.255.255 ! interface FastEthernet3/0/0  ip route-cache cef ! interface FastEthernet3/0/0.3  encapsulation dot1Q 10  xconnect 10.8.8.8 123 encap mpls pw-class atom-eth interface POS1/0/0  ip address 10.1.1.2 255.255.255.0  mpls ip  mpls label protocol ldp  clock source internal  crc 32 ! interface Loopback0  ip address 10.9.9.9 255.255.255.255 ! router ospf 10  nsf  network 10.9.9.9 0.0.0.0 area 0  network 10.1.1.2 0.0.0.0 area 0

Additional References

The following sections provide references related to AToM NSF.

Related Documents

Related Topic	Document Title
Stateful switchover	Stateful Switchover
MPLS Label Distribution Protocol	MPLS Label Distribution Protocol (LDP)
Cisco nonstop forwarding	Cisco Nonstop Forwarding
Any Transport over MPLS	Any Transport over MPLS
L2VPN Interworking configuration	L2VPN Interworking

Standards

Standards	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.	—

MIBs

MIBs	MIBs Link
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

RFCs	Title
RFC 3036	LDP Specification
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. 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

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Multiprotocol Label Switching Command Reference at http://www.cisco.com/en/US/docs/ios/mpls/command/reference/mp_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•debug acircuit checkpoint

•debug mpls l2transport checkpoint

•show acircuit checkpoint

•show mpls l2transport checkpoint

•show mpls l2transport vc

Feature Information for AToM NSF

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.

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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.

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Table 1 Feature Information for AToM NSF Any Transport over MPLS and AToM Graceful Restart

Feature Name	Releases	Feature Information
AToM NSF	12.2(25)S 12.2(28)SB 12.2(33)SRC	This feature uses NSF, SSO, and Graceful Restart to allow a Route Processor to recover from a disruption in control plane service without losing its MPLS forwarding state. In 12.2(25)S, this feature was introduced on the Cisco 7500 series router. In 12.2(28)SB, this feature was integrated into the release. In 12.2(33)SRC, this feature was integrated into the release for the Cisco 7600 router. Support for ISSU was added.

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All other trademarks mentioned in this document or website 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. (0907R)

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.

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