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Cisco IP Solution Center L2VPN and Carrier Ethernet User Guide, 6.0
OL-21636-01
Appendix D Terminating an Access Ring on Two N-PEs
Overview
Figure D-1 N-PE Redundancy, Starting at the U-PE
Figure D-2 N-PE and PE-AGG Redundancy, Starting at the U-PE
The first topology (N-PE redundancy starting at the U-PE, as shown in Figure D-1) provides the model
of fault recovery for the N-PE device. As shown in the diagram, there are two different outgoing
interfaces starting from the U-PE device. Each terminates at a different N-PE.
The second topology (N-PE and PE-AGG redundancy starting at the U-PE, as shown in Figure D-2)
provides fault recovery for both the PE-AGG and N-PE devices. The service switches over from the
primary to the secondary link when either the PE-AGG or the N-PE of the primary link fails.
For other network scenarios illustrating more complex topologies, see Additional Network
Configurations and Sample Configlets, page D-5.
The following list provides additional details about the implementation:
• Using one U-PE and two N-PEs consumes one access link (AL).
• When creating a service on a U-PE, the user specifies an NPC to be used. If the topology includes
an access ring with two N-PEs, then the service is configured on both N-PEs.
• For Ethernet over MPLS (EoMPLS) pseudowire (PW) services, if there is N-PE redundancy on both
sides of the service provider network, two pseudowires are created. One N-PE is defined as primary
and the other as secondary, in order to determine the how the pseudowires connect. If the user
enables the PW Redundancy option, the primary and secondary on either end are also connected
with pseudowire redundancy.
• For point-to-point (P2P) configurations, the two N-PEs use two separate pseudowires.
• ISC supports the case in which the service is configured identically (except for the access interface)
on both N-PEs. This saves the user from having to enter data twice because the link attributes in the
service request workflow are common for both N-PEs that are part of the attachment circuit.
• This feature is supported for both Cisco 7600 and Cisco ASR 9000 platforms. However, a single
service cannot include both 7600 and ASR 9000 platforms.
MPLS Core
N-PE-1
U-PE
204824
MPLS Core
N-PE-1
N-PE-2PE-AGG-2
PE-AGG-1
U-PE
204825