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How to Use Unified ISSU with Enhanced Mode

 
Summary

Use this document to learn about unified ISSU with enhanced mode and how to use it.

Unified ISSU with Enhanced Mode Overview

Enhanced mode is an in-service software upgrade (ISSU) option available on MPC7E, MPC8E, and MPC9E line cards that eliminates packet loss during the unified ISSU process. New architecture improvements on these line cards make it possible to have a second copy of the Junos OS software running on the line card in standby mode ready to take over while software moves from an old image to a new one during unified ISSU. You can enable enhanced mode by adding the enhanced-mode option to the request system software in-service-upgrade CLI command.

Benefits of Unified ISSU with Enhanced Mode

Unified ISSU with enhanced mode provides the following benefits:

  • Upgrades to a new software version with no loss of transit or host bound traffic

  • Reduces packet loss to zero or several milliseconds depending on configuration and network conditions

  • Allows software upgrades to be performed without the need for maintenance windows

  • Uses the existing unified ISSU process and doesn’t require any special configuration

Prerequisites for Performing Unified ISSU with Enhanced Mode

Before you begin a unified ISSU with enhanced mode, there are several prerequisites to keep in mind:

  • The device running unified ISSU with enhanced mode must use an MPC7E, MPC8E, or MPC9E line card.

    Note

    If you are performing unified ISSU with enhanced mode on a device that has a mix of supported and unsupported line cards, there will be sub-second traffic loss for traffic passing through the unsupported line cards.

    Note

    If you are performing unified ISSU with enhanced mode on guest network functions (GNFs), then all GNFs should be using MPC7E, MPC8E, or MPC9E line cards to avoid traffic loss.

  • The Linux version running on your Flexible PIC Concentrator (FPC) and the line card Linux version in the target release need to be compatible. Use the request system software validate in-service-upgrade package-name.tgz enhanced-mode CLI command to check compatibility.

  • Forwarding memory usage should be below 75 percent to ensure no packet loss during the unified ISSU process

    Note

    Unified ISSU with enhanced mode will still work if forwarding memory usage is above 75 percent, but it might introduce several milliseconds of packet loss.

  • All prerequisites for unified ISSU also apply to enhanced mode. See Unified ISSU System Requirements for more information.

You can check to see if your device can use unified ISSU with enhanced mode to upgrade to a specific release by using the request system software validate in-service-upgrade package-name.tgz enhanced-mode command. If your device and the target release are not compatible with enhanced mode, you can still use regular unified ISSU to upgrade with minimal disruption of traffic.

Performing Unified ISSU with Enhanced Mode

To perform a unified ISSU with enhanced mode, follow these steps:

  1. Download the software package by following the procedure in Downloading Software.

  2. Copy the software package or packages to the device. We recommend that you copy the file to the /var/tmp directory.

  3. Log in to the console connection. Using a console connection allows you to monitor the progress of the upgrade.

  4. Verify that you can use unified ISSU with enhanced mode for your desired release.

    • On the device, enter:

      where package-name.tgz is the name of the software package you downloaded in Step 1.

  5. Start the unified ISSU with enhanced mode:

    • On the device, enter:

      where package-name.tgz is the name of the software package you downloaded in Step 1.

    Note

    During the upgrade, you will not be able to access the Junos OS CLI.

    The device displays status messages similar to the following messages as the upgrade proceeds:

  6. Log in after the reboot of the device is completed. To verify that the software has been upgraded, enter the following command:

Note

When using unified ISSU with enhanced mode, the base Linux OS on your FPC cannot be upgraded as part of the ISSU process. Linux can be updated with an upgrade done through regular unified ISSU or a reboot of the FPC.

WHAT'S NEXT

Now that you understand how to run a unified ISSU with enhanced mode, you may want to read up on the unified ISSU process to understand what your device goes through during a unified ISSU. Check out Understanding the Unified ISSU Process for more information.