Which statement is correct about graceful Routing Engine switchover (GRES)?

Question

Options

• AThe PFE restarts and the kernel and interface information is lost.
• BGRES has a helper mode and a restarting mode.
• CWhen combined with NSR, routing is preserved and the new master RE does not restart rpd.
• DWith no other high availability features enabled, routing is preserved and the new master RE does

• A
  4% (1)
• B
  8% (2)
• C
  83% (20)
• D
  4% (1)

Explanation

The Graceful Routing Engine Switchover (GRES) feature in Junos OS enables a router with redundant Routing Engines to continue forwarding packets, even if one Routing Engine fails. GRES preserves interface and kernel information, ensuring that traffic is not interrupted. However, GRES does not preserve the control plane. To preserve routing during a switchover, GRES must be combined with either Graceful Restart protocol extensions or Nonstop Active Routing (NSR). When GRES is combined with NSR, nearly 75 percent of line rate worth of traffic per Packet Forwarding Engine remains uninterrupted during GRES. Any updates to the primary Routing Engine are replicated to the backup Routing Engine as soon as they occur. Therefore, when GRES is combined with NSR, routing is preserved and the new master RE does not restart rpd.

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