The unified in-service software upgrade (ISSU) feature enables you to upgrade between two different Junos OS releases with no disruption on the control plane and with minimal disruption of traffic.
NOTE:Unified ISSU is supported only on dual Routing Engine platforms.
NOTE:In addition, the graceful Routing Engine switchover (GRES) and nonstop active routing (NSR) features must be enabled.
Checks are made for the following:
Disk space is available for the /var file system on both Routing Engines.
The configuration is supported by a unified ISSU.
The PICs are supported by a unified ISSU.
Graceful Routing Engine switchover is enabled.
Nonstop active routing is enabled.
set routing-options nonstop-routing
set system commit synchronize
show task replication
request routing-engine login re1
show system switchover
show chassis in-service-upgrade
show chassis hardware
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