Getting Started with Unified In-Service Software Upgrade


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.

To quickly access the information you need, click on the link in Table 1.

Table 1: Locating the Information You Need to Work With ISSU

Task You Need to Perform

Where The Information Is Located

Verify unified ISSU support for your device

Unified ISSU System Requirements

Perform a unified ISSU

Example: Performing a Unified ISSU

Verify that the unified ISSU is successful

Verifying a Unified ISSU

Understand how the unified ISSU process works

Understanding the Unified ISSU Process

Unified ISSU takes advantage of the redundancy provided by dual Routing Engines and works in conjunction with the graceful Routing Engine switchover feature and the nonstop active routing feature.

Unified ISSU provides the following benefits:

  • Eliminates network downtime during software image upgrades

  • Reduces operating costs, while delivering higher service levels

  • Allows fast implementation of new features