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Hierarchy Level


(QFX5100 Virtual Chassis or Virtual Chassis Fabric [VCF] only) Optionally override the default algorithm that defines the number of parallel rcp sessions used for copying the new software image to member switches in a Virtual Chassis or VCF for nonstop software upgrade (NSSU).

You can upgrade the software running on all members of a Virtual Chassis or VCF using NSSU. At the beginning of the upgrade process, NSSU uses rcp to copy the new software from the primary switch to each of the member switches. Starting in Junos OS Release 14.1X53-D40, to minimize the time to copy the files to all members, NSSU uses parallel rcp sessions to copy the software to multiple members at the same time, rather than copying sequentially to each member in turn.

By default, the number of parallel rcp sessions that NSSU launches at a time follows an algorithm that optimizes the transfer time based on the total number of members in the Virtual Chassis or VCF, so that the new software is transferred to about half the members in parallel up to a maximum of 8 members at one time. After the first set of parallel copy operations are complete, NSSU launches the next set of parallel copy operations, and so on as needed until all members are updated.

Although the default value is usually optimal, you can configure the rcp-count statement to set a specific value for the number of parallel copy sessions instead. For example, you might want to use a lower number of parallel sessions to avoid potential impact on Virtual Chassis or VCF forwarding activity during NSSU.

After copying the new software to all members using as many parallel rcp sessions as needed, the NSSU process continues by rebooting each member with the new software in sequence, starting with the member in the backup Routing Engine role.


If copying the new software to any member fails, NSSU terminates the upgrade process for the entire Virtual Chassis or VCF, logs the error condition, and initiates an error recovery measure to remove the new software from the members to which it was already transferred.



Number of parallel rcp sessions for NSSU to launch at a time, which overrides the default algorithm.

Allowable values are 0 through 8. Specifying a value of 0 suppresses parallel copy sessions; the new software is copied to each member sequentially.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 14.1X53-D40.