ISSU and High Availability
This chapter describes the
in-service software upgrades (ISSU) and includes the following sections:
In a Cisco Nexus 9000 Series
chassis with dual supervisors, you can use the in-service software
upgrade (ISSU) feature to upgrade the system software while the system
continues to forward traffic. An ISSU uses the existing features of nonstop
forwarding (NSF) with stateful switchover (SSO) to perform the software upgrade
with no system downtime.
An ISSU is initiated through
the command-line interface (CLI) by an administrator. When initiated, an ISSU
updates (as needed) the following components on the system:
In a redundant system with
two supervisors, one of the supervisors is active while the other operates in
standby mode. During an ISSU, the new software is loaded onto the standby
supervisor while the active supervisor continues to operate using the old
software. As part of the upgrade, a switchover occurs between the active and
standby supervisors, and the standby supervisor becomes active and begins
running the new software. After the switchover, the new software is loaded onto
the (formerly active) standby supervisor.
following table shows the licensing requirements for ISSU:
The ISSU feature requires no license. Any feature not included in a license package is bundled with the nx-os image and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.
Guidelines and Limitations
An ISSU has the following
limitations and restrictions:
Do not change any
configuration settings or network connections during the upgrade. Any changes
in the network settings may cause a disruptive upgrade.
Configuration mode is blocked
during the ISSU to prevent any changes.
Only disruptive downgrades are supported. Non-disruptive downgrades are not
For more information about compatible upgrades and downgrades, see the Cisco Nexus 9000 Series NX-OS Release Notes. For more information about ISSU and the list of platforms for which it is supported, see the Cisco Nexus 9000 Series NX-OS Software Upgrade and Downgrade Guide.
How an ISSU Works
On a Cisco Nexus 9000 Series
chassis with two supervisors, the ISSU process follows these steps:
Begins when the administrator
Verifies the location and
integrity of the new software image file.
Verifies the operational
status and the current software versions of both supervisors and all switching
modules to ensure that the system is capable of an ISSU.
Loads the new software image
to the standby supervisor and brings it up to the HA ready state.
Forces a supervisor
Loads the new software image
to the (formerly active) standby supervisor and brings it up to the HA ready
Performs a nondisruptive
upgrade of each switching module.
During the upgrade process,
the system presents detailed status information on the console, requesting
administrator confirmation at key steps.
Determining ISSU Compatibility
An ISSU may be disruptive if
you have configured features that are not supported on the new software image.
To determine ISSU compatibility, use the
show incompatibility-all nxos
References for ISSU and High Availability
describes additional information related to ISSU and high availability.