GRES: VRRP (IPv4)

The graceful Routing Engine switchover (GRES) feature enables a router with redundant Routing Engines to continue forwarding packets, even if one Routing Engine fails. GRES preserves interface and kernel information. Traffic is not interrupted. However, GRES does not preserve the control plane. Any updates to the primary Routing Engine are replicated to the backup Routing Engine as soon as they occur. To preserve routing during a switchover, you must combine GRES with either of the following:

• Graceful restart protocol extensions 
• Nonstop active routing (NSR) 

This feature introduces GRES support in combination with VRRP IPv4.