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CLI-based Configuration Guide - Reliability

AR100-S, AR110-S, AR120-S, AR150-S, AR160-S, AR200-S, AR1200-S, AR2200-S, and AR3200-S V200R009

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Understanding NSR

Understanding NSR

This section describes principles of NSR.

Related Concepts

  • High availability (HA): supports a backup channel between the AMB and SMB.
  • Non-stop forwarding (NSF): enables uninterrupted traffic forwarding.
  • Non-stop routing (NSR): enables a specific device to use a standby control plane to restore services immediately if an active control plane fails, while the control planes of neighbor nodes do not detect the fault.
  • Active main board (AMB) and slave main board (SMB): implement control plane processes.
  • Line processing unit (LPU): implements forwarding plane processes.

NSR Procedure

The NSR process on the network shown in Figure 4-1 consists of the following phases:
  1. Batch backup: NSR is automatically enabled after the SMB starts. The AMB sends routing and forwarding information in batches to the SMB. A batch backup is performed before a real-time backup. NSR does not perform an AMB/SMB switchover during a batch backup.
  2. Real-time backup: Any updates to the control and forwarding planes can be backed up to the SMB in real time. NSR is ready to perform an AMB/SMB switchover to allow the SMB to take over traffic from the AMB if a fault occurs.
  3. AMB/SMB switchover: If the AMB fails, the SMB detects the failure and becomes the new AMB. The SMB instructs LPUs to send packets to the SMB itself. The AMB/SMB switchover is complete rapidly so that the routes between the local node and its neighbor nodes remain reachable.
Figure 4-1  NSR procedure

Table 4-1 describes the NSR procedure on a specific node.

Table 4-1  NSR procedure




Batch backup

Figure 4-2  Batch backup process

The SMB starts and sends a message about its in-service status to the AMB. After receiving the message, the AMB backs up its data in batches to the SMB.

  • If the AMB fails, the SMB can become a new AMB and restore data.

  • If the AMB fails before the batch backup is complete, the SMB cannot become a new AMB. The node then restarts automatically.

Real-time backup

Figure 4-3  Real-time backup process

If the neighbor status or routing information changes on the AMB, the AMB immediately sends updated information to the SMB.

AMB/SMB switchover

Figure 4-4  AMB/SMB switchover process

If software or hardware of the AMB fails, the SMB detects the failure and automatically becomes the new AMB. The new AMB uses the backup data to forward traffic. LPUs send the new AMB their information, including which has been updated during the AMB/SMB switchover. Routes are reachable and traffic forwarding is uninterrupted during the switchover.

Updated: 2019-05-17

Document ID: EDOC1000174116

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