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Understanding Software in a Junos Fusion Enterprise

This topic discusses the role of software in a Junos Fusion Enterprise. It covers:

Understanding Junos OS for the Aggregation Device in a Junos Fusion

An aggregation device in a Junos Fusion always runs Junos OS software and is responsible for almost all management tasks, including configuring all network-facing ports—the extended ports—on all satellite devices in the Junos Fusion. The extended ports in a Junos Fusion, therefore, typically support features that are supported by the version of Junos OS running on the aggregation device.

An aggregation device in a Junos Fusion runs the same Junos OS software regardless of whether it is or is not part of a Junos Fusion. Hence, Junos OS software is acquired, installed, and managed on an aggregation device in a Junos Fusion in the same manner that it is acquired, installed, and managed on a standalone device that is not part of a Junos Fusion.

Understanding Satellite Software for the Satellite Devices in a Junos Fusion

The satellite devices in a Junos Fusion run satellite software that has the built-in intelligence to extend features on the Junos OS software onto the satellite device. The satellite software is a Linux-based operating system that allows the satellite devices to communicate with the aggregation device for control plane data while also passing network traffic.

All satellite devices in a Junos Fusion must run satellite software that is compatible with the Junos OS software running on the aggregation device. See Junos Fusion Hardware and Software Compatibility Matrices for software compatibility requirements and links to the satellite software.

You can run the same version of satellite software on satellite devices that are different hardware platforms. For instance, if your Junos Fusion included EX2300 and EX4300 switches as satellite devices, the EX2300 and EX4300 switches acting as satellite devices could install the satellite software from the same satellite software package.

You can download satellite software from the software center for any satellite device. See the Junos Fusion Hardware and Software Compatibility Matrices, which provides software requirements as well as links to satellite device and Junos OS software. Additionally, you have the option to order some switches with the satellite software preinstalled from the factory.

The satellite software packages are stored on the aggregation device after a satellite software package installation—which is typically managed from the aggregation device—has been executed. The satellite software packages remain in the file system even if the Junos OS on the aggregation device is upgraded. The satellite software on a satellite device can be updated individually or, more commonly, using satellite software upgrade-groups, which are discussed in more detail in this document.

A device cannot simultaneously run Junos OS and the satellite software. If you remove a satellite device from a Junos Fusion, you have to install the Junos OS onto the device before you can use it in your network as a standalone Junos switch.

Satellite software is sometimes referred to as satellite network operating system (SNOS) software in the command-line interface and in other documentation.

The satellite software requirements for a Junos Fusion Enterprise are discussed in Understanding Junos Fusion Enterprise Software and Hardware Requirements.

Understanding Satellite Software Upgrade Groups

A satellite software upgrade group is a group of satellite devices that are designated to upgrade to the same satellite software version. One Junos Fusion can contain multiple software upgrade groups, and multiple software upgrade groups should be configured in most Junos Fusions to avoid network downtimes during satellite software installations.

When a satellite device is added to a Junos Fusion, the aggregation device checks if the satellite device is using an FPC ID that is included in a satellite software upgrade group. If the satellite device is using an FPC ID that is part of a satellite software upgrade group, the device upgrades its satellite software to the version of software associated with the satellite software upgrade group - unless it is already running the defined version.

When the satellite software package associated with an existing satellite software group is changed, the satellite software for all member satellite devices is upgraded using a throttled upgrade. The throttled upgrade ensures that the aggregation device is not overwhelmed with providing satellite software simultaneously to many satellite devices.

When satellite devices of a satellite device cluster are upgraded, members of the same satellite device cluster download the software to be used and install the software at the same time as other members of the cluster. This ensures that cluster members run the same version of software as each other in case there are incompatibilities between satellite software versions.

The two most common methods of installing satellite software onto a Junos switch—autoconverting a device into a satellite device when it is cabled into an aggregation device and manually converting a device that is cabled into an aggregation device into a satellite device—require the presence of a configured satellite software upgrade group.

Software upgrade groups are configured and managed on the aggregation device.

Understanding Satellite Software Requirements for a Satellite Device Cluster

All satellite devices in a satellite device cluster are associated with a single satellite software upgrade group, which is automatically created when a satellite device cluster is configured as part of a Junos Fusion. The satellite software upgrade group uses the same name as the satellite device cluster name, and ensures that all satellite devices in the cluster run the same version of satellite software.

The automatically created software upgrade group for the satellite device cluster is managed like any other software upgrade group.

Understanding Satellite Software Requirements in a Dual Aggregation Device Topology

In a Junos Fusion with dual aggregation devices, you must ensure that only one version of satellite software is associated with each satellite software upgrade group.

When configuring a Junos Fusion into a dual aggregation topology, do one of the following to ensure satellite software is properly maintained:

  • Configure all satellite software upgrade groups on one of the aggregation devices.

  • Configure the exact same satellite software upgrade group—a satellite software upgrade group with the same name and same FPC ID associations—on both aggregation devices.

If there is a mismatch between satellite software upgrade group membership or satellite software version for a satellite software upgrade group, satellite software is not upgraded on any satellite devices in the upgrade group until the configuration and version association is addressed.

Understanding the Platform Specific Satellite Software Image

The platform specific satellite software package is required to install satellite software onto an EX2300, EX3400 or EX4300 switch that is not connected to an aggregation device. Use the platform specific satellite software package when you want to manually install satellite software on a switch using the request chassis device-mode satellite URL-to-satellite-software command before you interconnect that switch into a Junos Fusion Enterprise.


Platform specific satellite software is not required for QFX5100 switches.

You can identify the platform specific satellite software by looking for the satellite-ppc prefix in the satellite software image name; for example, satellite-ppc-3.0R1.1-signed.tgz. To find the image that is compatible with your satellite device, please refer to Junos Fusion Hardware and Software Compatibility Matrices.