Juniper Virtual Chassis Non-Stop Software Upgrade

request system software nonstop-upgrade <package-name>

<force-host>

<no-copy>

<no-old-master-upgrade>

<reboot>

<unlink>

The following requirements apply to Virtual Chassis or mixed Virtual Chassis:

• All Virtual Chassis or mixed Virtual Chassis members and all Routing Engines must be running the same Junos OS release.
• Graceful Routing Engine switchover (GRES) must be enabled.
• For minimal traffic disruption, you must define link aggregation groups (LAGs) such that the member links reside on different Virtual Chassis or mixed Virtual Chassis members or on different line cards.

The following are requirements for Virtual Chassis or mixed Virtual Chassis members:

• The Virtual Chassis or mixed Virtual Chassis members must be connected in a ring topology so that no member is isolated as a result of another member being rebooted. This topology prevents the Virtual Chassis from splitting during an NSSU.
• The Virtual Chassis or mixed Virtual Chassis master and backup must be adjacent to each other in the ring topology. Adjacency permits the master and backup to always be in sync, even when the switches in linecard roles are rebooting.
• The Virtual Chassis or mixed Virtual Chassis must be preprovisioned so that the linecard role has been explicitly assigned to member switches acting in a linecard role. During an NSSU, the Virtual Chassis and mixed Virtual Chassis members must maintain their roles—the master and backup must maintain their master and backup roles (although mastership will change), and the remaining switches must maintain their linecard roles.
• A two-member Virtual Chassis or mixed Virtual Chassis must have no-split-detection configured so that the Virtual Chassis or mixed Virtual Chassis does not split when an NSSU upgrades a member.

How an NSSU Works

When you request an NSSU on an a Virtual Chassis or mixed Virtual Chassis:

1. The Virtual Chassis or mixed Virtual Chassis master verifies that:
   • The backup is online and running the same software version.
   • Graceful Routing Engine switchover (GRES) is enabled.
   • The Virtual Chassis or mixed Virtual Chassis member has a preprovisioned configuration.
2. The master installs the new software image on the backup and reboots it.
3. The master resynchronizes the backup.
4. The master installs the new software image on member switches that are in the line card role and reboots them, one at a time. The master waits for each member to become online and active before starting the software upgrade on the next member.
5. When all members that are in the line card role have been upgraded, the master performs a graceful Routing Engine switchover, and the upgraded backup becomes the master.
6. The software on the original master is upgraded and the original master is automatically rebooted. After the original master has rejoined the Virtual Chassis, you can optionally return control to it by requesting a graceful Routing Engine switchover.