L2VPNs can provide pseudowire resiliency through their routing protocols. When connectivity between end-to-end PE devices fails, the L2VPN pseudowire redundancy can select and alternate path to the directed LDP session and the user data can take over. However, there are some parts of the network where this rerouting mechanism does not protect against interruptions in service. The figure below shows those parts of the network that are vulnerable to an interruption in service.
Figure 1. Points of Potential Failure in an L2VPN Network
The L2VPN Pseudowire Redundancy feature provides the ability to ensure that the CE2 device in the figure above can always maintain network connectivity, even if one or all the failures in the figure occur.
The L2VPN Pseudowire Redundancy feature enables you to set up backup pseudowires. You can configure the network with redundant pseudowires (PWs) and redundant network elements, which are shown in the three figures below.
The figure below shows a network with redundant pseudowires and redundant attachment circuits.
Figure 2. L2VPN Network with Redundant PWs and Attachment Circuits
The figure below shows a network with redundant pseudowires, attachment circuits, and CE devices.
Figure 3. L2VPN Network with Redundant PWs, Attachment Circuits, and CE devices
The figure below shows a network with redundant pseudowires, attachment circuits, CE devices, and PE devices.
Figure 4. L2VPN Network with Redundant PWs, Attachment Circuits, CE devices, and PE devices