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.

• Before configuring the H-VPLS N-PE Redundancy for QinQ and MPLS Access feature, configure your H-VPLS network and make sure it is operating correctly. For more information about configuring the H-VPLS network, see the " Configuring VPLS" section in Configuring Multiprotocol Label Switching on the Optical Services Modules .
• Make sure that the PE-to-customer edge (CE) interface is configured with a list of allowed VLANs. For more information, see the " Configuring VPLS" section in Configuring Multiprotocol Label Switching on the Optical Services Modules .
• To provide faster convergence, you can enable the MPLS Traffic Engineering: Fast Reroute feature in the Multiprotocol Label Switching (MPLS) core. For more information about MPLS traffic engineering, see the "MPLS Traffic Engineering (TE)--Fast Reroute (FRR) Link and Node Protection" section in the Cisco IOS Multiprotocol Label Switching Configuration Guide .
• Enable the L2VPN Pseudowire Redundancy feature on the U-PE routers for MPLS access. For information about configuring the L2VPN Pseudowire Redundancy feature, see the "L2VPN Pseudowire Redundancy" section in the Cisco IOS Wide-Area Networking Configuration Guide .
• When configuring Multiple Spanning Tree Protocol (MSTP), specify that one of the N-PE routers is the root by assigning it the lowest priority using the spanning-tree mst instance-id priority prioritycommand.

For information about configuring MSTP, see the "Configuring MST Instance Parameters" section in the Cisco 7600 Series Cisco IOS Software Configuration Guide.

• When configuring MSTP, make sure that each router participating in the spanning tree is in the same region and is the same revision by issuing the revision, name, and instance commands in MST configuration mode. For more information on configuring these MSTP parameters, see the " Configuring Spanning Tree and IEEE 802.1s MST" section in the Cisco 7600 Series Cisco IOS Software Configuration Guide.

• The H-VPLS N-PE Redundancy for QinQ and MPLS Access feature cannot be used with the VPLS Autodiscovery feature on pseudowires that attach to U-PE routers. When you create the VPLS, you can manually create the virtual forwarding interface (VFI).
• You cannot configure more than one pseudowire to carry the bridge protocol data unit (BPDU) information between the N-PE routers. If you attempt to enter the forward permit l2protocol all command for multiple VFIs, an error message is displayed.
• You cannot configure a local loopback address as a neighbor when you configure the H-VPLS N-PE Redundancy for QinQ and MPLS Access feature on N-PE routers. If you do so, the following error is displayed:

VPLS local switching to peer address not supported

• Only two N-PE routers can be connected to each U-PE router.
• For a list of supported hardware for this feature, see the Release Notes for Cisco IOS Release 12.2SR for the Cisco 7600 Series Routers.
• The spanning-tree mode must be MSTP for the H-VPLS N-PE Redundancy for QinQ and MPLS Access feature. If the spanning-tree mode changes, the H-VPLS N-PE Redundancy for QinQ and MPLS Access feature may not work correctly, even though the pseudowire that carries the BPDU information still exists and the H-VPLS N-PE Redundancy feature is still configured.

• How H-VPLS N-PE Redundancy for QinQ and MPLS Access Works
  
• VPLS MAC Address Withdrawal
  

• Configuring the VPLS Pseudowire Between the N-PE Routers
  
• Configuring the SVI for the Native VLAN
  

• Example H-VPLS N-PE Redundancy for QinQ Access
  

CE router --customer edge router. A router that belongs to a customer network, which connects to a PE router to utilize MPLS VPN network services.

LAN --local-area network. High-speed, low-error data network covering a relatively small geographic area. LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited areas.

MPLS --Multiprotocol Label Switching. A packet-forwarding technology, used in the network core, that applies data link layer labels to tell switching nodes how to forward data, resulting in faster and more scalable forwarding than network layer routing normally can do.

MSTP --Multiple Spanning Tree Protocol. MSTP enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the number of spanning-tree instances needed to support a large number of VLANs.

N-PE --network provider edge router. This router acts as a gateway between the MPLS core and edge domains.

PE router --provider edge router. The PE router is the entry point into the service provider network. The PE router is typically deployed on the edge of the network and is administered by the service provider.

pseudowire --A pseudowire is a virtual connection that, in the context of VPLS, connects two SVIs. It is a mechanism that carries the elements of an emulated service from one PE router to one or more PE routers over a packet switched network (PSN). A pseudowire is bidirectional and consists of a pair of unidirectional MPLS virtual circuits (VCs). A pseudowire can be used to connect a point-to-point circuit.

QinQ --An IEEE 802.1Q VLAN tunnel. A mechanism for constructing multipoint Layer 2 VPN using Ethernet switches.

redundancy --The duplication of devices, services, or connections so that, in the event of a failure, they can perform the work of those that failed.

router --A network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.

spanning tree --Loop-free subset of a network topology.

U-PE --user provider edge router. This router connects CE routers to the service.

VFI --virtual forwarding instance. A VFI is a collection of data structures used by the data plane, software-based or hardware-based, to forward packets to one or more VCs.

VLAN --Virtual LAN. Group of devices on one or more LANs that are configured (using management software) so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments.

VPLS --Virtual Private LAN Service. VPLS describes an architecture that delivers Layer 2 service that emulates an Ethernet LAN across a wide-area network (WAN) and inherits the scaling characteristics of a LAN.

VPLS redundancy --Also called N-PE redundancy. Allows U-PEs to be dual-honed (to their N-PEs) in a loop-free topology with MPLS or QinQ as the access or aggregation domain.

VPN --Virtual Private Network. Allows IP traffic to travel securely over public TCP/IP networks and the Internet by encapsulating and encrypting all IP packets. VPN uses a tunnel to encrypt all information at the IP level.