Nexus – Performing ISSU

What is an ISSU?

Cisco NX-OS software supports in-service software upgrades (ISSUs) on devices with dual supervisor modules.  An ISSU can update the software images on your device without disrupting data traffic. Only control traffic is disrupted.

An ISSU updates the following images:

  • Kickstart image
  • System image
  • Supervisor module BIOS
  • Data module image
  • Data module BIOS
  • Connectivity management processor (CMP) image

ISSU Process is outlined below


VDC Support

When you upgrade the Cisco NX-OS software, you upgrade the software for all virtual device contexts (VDCs) on the physical device. You cannot upgrade the Cisco NX-OS software for an individual VDC.

Parallel Upgrade

Starting with Cisco NX-OS Release 5.2(1), multiple linecards can be simultaneously upgraded, and the infrastructure support is available. This decreases the ISSU time when compared with an ISSU upgrade that is done serially (one card at a time).

To start a parallel upgrade, use the following command: install all kickstart image system image parallel

Up to three linecards can be upgraded in parallel with this command.


Prerequisites for Upgrading the Cisco NX-OS Software

Use the show configuration session summary command to verify that you have no active configuration sessions.

Cisco NX-OS Software Upgrade Guidelines



Schedule the upgrade when your network is stable and steady. Ensure that everyone who has access to the device or the network is not configuring the device or the network during this time. You cannot configure a device during an upgrade.


Verify that sufficient space is available in the location where you are copying the images. This location includes the active and standby supervisor module bootflash: (internal to the device). Internal bootflash: has approximately 250 MB of free space available.


Avoid power interruption during any install procedure, which can corrupt the software image.

Connectivity to remote servers

Configure the IPv4 address or IPv6 address for the 10/100/1000 BASE-T Ethernet port connection (interface mgmt0).

Ensure that the device has a route to the remote server. The device and the remote server must be in the same subnetwork if you do not have a router to route traffic between subnets.

Software images

Ensure that the specified system and kickstart images are compatible with each other.

If the kickstart image is not specified, the device uses the current running kickstart image.

If you specify a different system image, ensure that it is compatible with the running kickstart image.

Retrieve the images in one of two ways:


Images are locally available on the switch.


Images are in a remote location and you specify the destination using the remote server parameters and the filename to be used locally.

ISSU Failure Conditions

The following situations cause the installation to fail to complete:

  • If the standby supervisor module bootflash: file system does not have sufficient space to accept the updated image.
  • If the specified system and kickstart images are not compatible.
  • If the network or device is configured while the upgrade is in progress.
  • If a Spanning Tree Protocol (STP) topology change occurs while the upgrade is in progress.
  • If the install all command is entered on the standby supervisor module.
  • If the install all command does not reference the default bootflash: in a dual supervisor module configuration.
  • If a module is removed while the upgrade is in progress.
  • If the device has any power disruption while the upgrade is in progress.
  • If the entire path for the remote server location is not specified accurately.
  • If some FEX ports are operating in LACP fast rate mode.
  • If images are incompatible after an upgrade. For example, an I/O module image may be incompatible with the system image, or a kickstart image may be incompatible with a system image. This is also identified by theshow install all impact command in the compatibility check section of the output (under the Bootable column).
  • If a linecard is in failure state, the ISSU will abort.


Upgrading a Device with Dual Supervisor Modules

The install all command supports in-service software upgrades (ISSUs) on devices that have dual supervisor modules and performs the following actions:

  • Determines whether the upgrade will be disruptive and asks if you want to continue.
  • Ensure that you have enough space in the standby bootflash.
  • Copies the kickstart and system images to the standby supervisor module.
  • Sets the KICKSTART and SYSTEM boot variables.
  • Reloads the standby supervisor module with the new Cisco NX-OS software.
  • Reloads the active supervisor module with the new Cisco NX-OS software, which causes a switchover to the newly upgraded standby supervisor module.
  • Upgrades the line cards.
  • The Connectivity Management Processor (CMP) on both supervisors will get upgraded.


Upgrade Procedure Summary

Upgrade Procedure Summary

Step 1 Back up configurations

Step 2 Log in to the console port on both of the active and standby supervisor modules.

Step 3 Log in to and download the latest Cisco NX-OS kickstart and system images to a server.

Step 4 Download the Cisco NX-OS kickstart and system images from the server to your device using the copy command.

Step 5 Save the device configuration using the copy running-config startup-config vdc-all command.

Step 6 Enter the install all command at the active supervisor command prompt to upgrade the Cisco NX-OS software on your device.

Note      A supervisor module switchover occurs during the software installation.

switch# install all kickstart n7000-s1-kickstart.7.2.0.D1.1.bin system n7000-s1-dk9.7.2.0.D1.1.bin

The above procedures and information was provided my Cisco’s technical documents found on their web site. It’s mostly prep work before performing an ISSU, and quit easy to execute. Good luck.




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