Understanding How Gres Enables Uninterrupted Packet Forwarding During A Routing Engine Switchover; Understanding Graceful Routing Engine Switchover; Graceful Routing Engine Switchover Concepts; Understanding How Gres Enables Uninterrupted Packet Forwarding - Juniper EX9200 Features Manual

CHAPTER 1
Understanding How GRES Enables
Uninterrupted Packet Forwarding During
a Routing Engine Switchover

Understanding Graceful Routing Engine Switchover

Graceful Routing Engine Switchover Concepts

Copyright © 2017, Juniper Networks, Inc.
Understanding Graceful Routing Engine Switchover on page 3
This topic contains the following sections:
Graceful Routing Engine Switchover Concepts on page 3
Effects of a Routing Engine Switchover on page 8
The graceful Routing Engine switchover (GRES) feature in Junos OS enables a routing
platform 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.
NOTE: On T Series routers, TX Matrix routers, and TX Matrix Plus routers, the
control plane is preserved in case of GRES with nonstop active routing (NSR),
and nearly 75 percent of line rate worth of traffic per Packet Forwarding
Engine remains uninterrupted during GRES.
Neighboring routers detect that the router has experienced a restart and react to the
event in a manner prescribed by individual routing protocol specifications.
To preserve routing during a switchover, GRES must be combined with either:
Graceful restart protocol extensions
Nonstop active routing
Any updates to the master Routing Engine are replicated to the backup Routing Engine
as soon as they occur.
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