Cisco Catalyst 4500 Series Configuration Manual page 249

Configuring the Cisco IOS XE In Service Software
Upgrade Process
ISSU is available in Cisco IOS XE Release 3.1.0.SG and later releases.
Note
Operating on redundant systems, the In Service Software Upgrade (ISSU) process allows Cisco IOS XE
software to be updated or otherwise modified while packet forwarding continues. In most networks,
planned software upgrades are a significant cause of downtime. ISSU allows Cisco IOS XE software to
be upgraded while packet forwarding continues. This increases network availability and reduces
downtime caused by planned software upgrades. This document provides information about ISSU
concepts and describes the steps taken to perform ISSU in a system.
Topics include:
Prerequisites to Performing ISSU, page 6-2
•
About Performing ISSU, page 6-3
•
• How to Perform the ISSU Process, page 6-15
• Cisco High Availability Features in Cisco IOS XE 3.1.0SG, page 6-35
Note For complete syntax and usage information for the switch commands used in this chapter, first look at
the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:
http://www.cisco.com/en/US/products//hw/switches/ps4324/index.html
If the command is not found in the Catalyst 4500 Series Switch Command Reference, it will be found in
the larger Cisco IOS library. Refer to the Cisco IOS Command Reference and related publications at this
location:
http://www.cisco.com/en/US/products/ps6350/index.html
OL-25340-01
C H A P T E R
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
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6-1