Understanding Software Installation on EX Series Switches

Overview of the Software Installation Process

An EX Series switch is delivered with Junos OS preinstalled. When you connect power to the switch, it starts (boots) up from the installed software.

You upgrade Junos OS on an EX Series switch by copying a software package to your switch or another system on your local network, then use either the J-Web interface or the CLI to install the new software package on the switch. Finally, you reboot the switch; it boots from the upgraded software. After a successful upgrade, you should back up the new current configuration to a secondary device.

During a successful upgrade, the upgrade package removes all files from /var/tmp and completely reinstalls the existing software. It retains configuration files, and similar information, such as secure shell and host keys, from the previous version. The previous software package is preserved in a separate disk partition, and you can manually revert back to it if necessary. If the software installation fails for any reason, such as loss of power during the installation process, the system returns to the originally active installation when you reboot.

Software Package Security

All Junos OS releases are delivered in signed packages that contain digital signatures to ensure official Juniper Networks software. For more information about signed software packages, see the Junos OS Installation and Upgrade Guide.

Installing Software on a Virtual Chassis

You can connect individual EX Series switches together to form one unit and manage the unit as a single device, called a Virtual Chassis. The Virtual Chassis operates as a single network entity composed of members. Each member of a Virtual Chassis runs a Junos OS package. Supported Virtual Chassis include EX4200 Virtual Chassis, EX4500 Virtual Chassis, mixed EX4200 and EX4500 Virtual Chassis, or EX8200 Virtual Chassis.

For ease of management, a Virtual Chassis provides flexible methods to upgrade software releases. You can deploy a new software release to all members of a Virtual Chassis or to only a particular member.

You can also upgrade the software on an EX8200 Virtual Chassis using nonstop software upgrade (NSSU). Unlike a standard software upgrade, NSSU does not require a reboot of the Virtual Chassis. Instead, it takes advantage of graceful Routing Engine switchover and nonstop active routing (NSR) to ensure no disruption to the control plane during the upgrade. You can minimize disruption to network traffic by defining link aggregation groups (LAGs) such that the member links of each LAG reside on different line cards. The line cards are upgraded one at a time, so that traffic continues to flow through the other line cards while a line card is being upgraded.

Installing Software on EX8200 Switches with Redundant Routing Engines

• Perform a nonstop software upgrade (NSSU)—An NSSU upgrades both Routing Engines with a single command and with a minimum of network disruption. An NSSU takes advantage of graceful Routing Engine switchover (GRES) and nonstop active routing (NSR) to ensure no disruption to the control plane. You can minimize disruption to network traffic by defining link aggregation groups (LAGs) such that the member links of each LAG reside on different line cards. The line cards are upgraded one at a time, so that traffic continues to flow through the other line cards while a line card is being upgraded.

  You cannot use NSSU to downgrade the software running on a switch.

  For more information about NSSU, see Understanding Nonstop Software Upgrade on EX Series Switches.

• Upgrade each Routing Engine manually—You can perform a Junos OS installation on each Routing Engine separately, starting with the backup Routing Engine. You can use this procedure to downgrade the software running on a switch. See Installing Software on an EX Series Switch with Redundant Routing Engines (CLI Procedure).

Installing Software Using Automatic Software Download

The automatic software download feature uses the DHCP message exchange process to download and install software packages. Users can define a path to a software package on the DHCP server and then the DHCP server communicates this path to EX Series switches acting as DHCP clients as part of the DHCP message exchange process. The DHCP clients that have been configured for automatic software download receive these messages and, when the software package name in the DHCP server message is different from that of the software package that booted the DHCP client switch, download and install the software package. See Upgrading Software Using Automatic Software Download on EX Series Switches.

Troubleshooting Software Installation

If the Junos OS loads but the CLI is not working for any reason, or if the switch has no software installed, you can use the recovery installation procedure to install the software on the switch. See Troubleshooting Software Installation.

Note: You can also use this procedure to load two versions of Junos OS in separate partitions on the switch.