Unified In-Service Software Upgrade (ISSU) on Juniper

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 chassis redundancy graceful-switchover 

set routing-options nonstop-routing 

set system commit synchronize 

commit 

show task replication 

 request routing-engine login re1 

 show system switchover 

show chassis in-service-upgrade 

show chassis hardware 

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