Juniper EX9200 Features Manual page 25

Chapter 1: Understanding How GRES Enables Uninterrupted Packet Forwarding During a Routing Engine Switchover
Copyright © 2017, Juniper Networks, Inc.
NOTE: Successive Routing Engine switchover events must be a minimum of
240 seconds (4 minutes) apart after both Routing Engines have come up.
If the router or switch displays a warning message similar to
Engine is not ready for graceful switchover. Packet Forwarding Engines that are
not ready for graceful switchover might be reset
If you choose to proceed with switchover, only the Packet Forwarding Engines
that were not ready for graceful switchover are reset. None of the FPCs should
spontaneously restart. We recommend that you wait until the warning no
longer appears and then proceed with the switchover.
NOTE: Starting from Junos OS Release 14.2, when you perform GRES on
MX Series routers, you must execute the
operational mode command on the new master Routing
wait-to-restore
Engine to clear the wait-to-restore timer on it. This is because the
synchronous-ethernet wait-to-restore
wait-to-restore timer only on the local Routing Engine.
NOTE: In a routing matrix with TX Matrix Plus router with 3D SIBs, for
successive Routing Engine switchover, events must be a minimum of 900
seconds (15 minutes) apart after both Routing Engines have come up.
GRES must be performed on one line-card chassis (LCC) (of a TX Matrix
router with 3D SIBs) at a time to avoid synchronization issues.
NOTE:
We do not recommend performing a commit operation on the backup
Routing Engine when GRES is enabled on the router or switch.
We do not recommend enabling GRES on the backup Routing Engine in
any scenario.
NOTE: On QFX10000 switches, we strongly recommend that you configure
the
nsr-phantom-holdtime seconds
hierarchy level when nonstop routing is enabled with GRES. Doing so helps
to prevent traffic loss. When you configure this statement, phantom IP
addresses remain in the kernel during a switchover until the specified
hold-time interval expires. After the interval expires, these routes are added
to the appropriate routing tables. In an Ethernet VPN (EVPN)/VXLAN
environment, we recommend that you specify a hold-time value of 300
seconds (5 minutes).
Standby Routing
. Do not attempt switchover.
clear synchronous-ethernet
operational mode command clears the
statement at the
[edit routing-options]
clear
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