Table Of Contents
NSF/SSO—Any Transport over MPLS and AToM Graceful Restart
First Published: August 11, 2004Last Updated: June 25, 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.
Note In this document, the NSF/SSO—Any Transport over MPLS and AToM Graceful Restart feature is referred to as AToM NSF for brevity.
In Cisco IOS XE software, AToM NSF supports the following attachment circuits:
•Ethernet to Ethernet VLAN interworking
Finding Feature Information
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 XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
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 for information on configuring AToM. For configuring L2VPN Interworking, see the L2VPN Interworking feature module.
•SSO has been configured on the RPs. 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 the following:
–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.
•AToM NSF requires that neighbor networking devices be able to perform AToM GR.
Restrictions for AToM NSF
•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.
Information About AToM NSF
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 for AToM NSF
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.
NSF/SSO Support for Ethernet to Ethernet VLAN Interworking
The NSF/SS0—Ethernet to Ethernet VLAN Interworking features enables SSO and NSF capabilities for Ethernet to VLAN attachment circuits. Changes in the learned MAC address for interworking are reflected on the standby RP so that identical values exist on the active and standby RPs.
ISSU Support for AToM NSF
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 XE 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.
How to Configure AToM NSF
There is no AToM-specific configuration for AToM NSF. Before you configure AToM NSF, you need to configure MPLS LDP Graceful Restart. You enable MPLS LDP Graceful Restart to assist a neighboring router configured with AToM NSF to maintain its forwarding state while the LDP session is disrupted. See the LDP Graceful Restart document for information about how MPLS LDP Graceful Restart works and how you can customize it for your network.
MPLS LDP Graceful Restart is enabled globally. When you enable MPLS LDP Graceful Restart, it has no effect on existing LDP sessions. MPLS LDP Graceful Restart is enabled for new sessions that are established after the feature has been globally enabled.
This section contains the following task:
•Configuring MPLS LDP Graceful Restart (required)
Configuring MPLS LDP Graceful Restart
2. configure terminal
3. ip cef distributed
4. mpls ldp graceful-restart
5. interface type slot/subslot/port[.subinterface-number]
6. mpls ip
7. mpls label protocol ldp
Configuration Examples for AToM NSF
Example: Ethernet to VLAN Interworking with AToM NSF
The following example shows how to configure AToM NSF on two PE routers:
PE1ip cef distributed!redundancymode sso!boot system flash disk2:rsp-pv-mz!mpls ldp graceful-restartmpls ipmpls label protocol ldpmpls ldp router-id Loopback0 forcempls ldp advertise-labels!pseudowire-class atom-ethencapsulation mplsinterworking ethernet!interface Loopback0ip address 10.8.8.8 255.255.255.255!interface FastEthernet1/1/0xconnect 10.9.9.9 123 encap mpls pw-class atom-ethinterface POS0/1/0ip address 10.1.1.1 255.255.255.0mpls ipmpls label protocol ldpclock source internalcrc 32!interface Loopback0ip address 10.8.8.8 255.255.255.255no shutdown!router ospf 10nsfnetwork 10.8.8.8 0.0.0.0 area 0network 10.19.1.1 0.0.0.0 area 0
PE2ip cef distributed!redundancymode sso!boot system flash disk2:rsp-pv-mzmpls ldp graceful-restartmpls ipmpls label protocol ldpmpls ldp router-id Loopback0 forcempls ldp advertise-labels!pseudowire-class atom-ethencapsulation mplsinterworking eth!interface Loopback0ip address 10.9.9.9 255.255.255.255!interface FastEthernet0/3/0ip route-cache cef!interface FastEthernet0/3/0.3encapsulation dot1Q 10xconnect 10.8.8.8 123 encap mpls pw-class atom-ethinterface POS1/0/0ip address 10.1.1.2 255.255.255.0mpls ipmpls label protocol ldpclock source internalcrc 32!interface Loopback0ip address 10.9.9.9 255.255.255.255!router ospf 10nsfnetwork 10.9.9.9 0.0.0.0 area 0network 10.1.1.2 0.0.0.0 area 0
Related Topic Document Title
Cisco IOS commands
MPLS Label Distribution Protocol
Cisco nonstop forwarding
Any Transport over MPLS
L2VPN Interworking configuration
MPLS AToM and LDP commands
High availability commands
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
MIBs MIBs Link
MPLS Label Distribution Protocol MIB Version 8 Upgrade
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:
Feature Information for AToM NSF
Table 1 lists the features in this module and provides links to specific configuration information.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE 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.
Note Table 1 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.
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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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