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Feature Description - VPN 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Feature Description - VPN
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VPN non-stop routing (NSR) is a technique which ensures that if an active main board (AMB) failure causes the control plane of a specific node to fail, the node retains its control plane connections to neighboring nodes and ensures uninterrupted traffic transmission on the forwarding plane.


Carriers have increasing demands for IP network reliability. Conventional non-stop forwarding (NSF) and GR techniques cannot prevent traffic interruptions if a neighboring node does not support GR or multiple nodes fail simultaneously during a GR process. Interruptions occur because a GR-enabled node cannot obtain routing information from or establish control plane connections to neighboring nodes during the GR process. As a result, traffic is interrupted temporarily before the GR process is complete.

NSR can be used to ensure uninterrupted traffic transmission and retain control plane connections if a software or hardware fault occurs on the control plane. The control planes of neighboring nodes are unaware of the fault during the NSR process.

Related Concepts

  • HA: supports a backup channel between the AMB and standby main board (SMB).
  • NSR: allows a standby control plane to take over traffic from an active control plane if the active control plane fails, although; whereas preventing the control planes of neighbor nodes from detecting the fault.
  • NSF: enables a node to use the GR mechanism to ensure uninterrupted transmission during an AMB/SMB switchover.
  • AMB and SMB: implement control plane processes.


The AMB backs up VPN data to the SMB on a specific node to implement NSR. The following key VPN data is synchronized between the AMB and SMB:
  • VPN routes, including:
    • Routes imported by running the import-route or network command in the BGP-VPN instance IPv4 address family view or BGP-VPN instance IPv6 address family view

    • Locally crossed routes

    • Remotely crossed routes

  • Attributes carried by routes

  • VPN labels

  • Next hop information about routes


Active and standby control planes must be able to run on different boards of an NSR-capable device.

The NSR process is as follows:
  1. Batch backup

    The AMB backs up VPN data in batches to the SMB immediately after the SMB starts.

  2. Real-time backup

    The AMB backs up VPN data in real time to the SMB. Both the AMB and SMB receive packets to implement real-time data synchronization between them.

  3. Switchover

    If the AMB fails, the SMB takes over services. The SMB retains uninterrupted operation of both the control and forwarding planes because the SMB has the same data as the AMB.


For details about NSR, see chapter "NSR" in NE deviceMid-End RouterFeature Description - Reliability.

Other Usage

An NSR-enabled device can function as a GR helper. The GR helper communicates with NSR-disabled devices and responds to neighboring nodes' GR requests during an AMB/SMB switchover.

Usage Scenario

NSR is enabled on a node (for example, PE3 shown in Figure 5-43) when the node has multiple links that load-balance traffic. NSR helps prevent traffic interruptions that result from a single point of failure.

Figure 5-43 shows a typical NSR application.
Figure 5-43 Typical VPN NSR application

NSR minimizes the impact of control plane faults and prevents route flapping on heavily loaded networks.


NSR offers the following benefits:

  • NSR ensures the uninterrupted operation of the forwarding plane and allows a standby control plane to retain connections between a local node and its neighboring nodes if the VPN control plane of the local node fails.
  • A VPN node can use NSR to work independently without the assistance of neighboring nodes. NSR can help multiple VPN nodes implement AMB/SMB switchovers if control planes of these nodes over an MPLS network fail.
Updated: 2019-01-14

Document ID: EDOC1100058940

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