In Service Soft Upgrade (ISSU) Deployment Guide and Case Study

Cisco ASR 1000 Series Aggregation Services Routers

By Cisco Systems

Published 2008; Posted February 2009


In most networks, a significant cause of downtime is planned maintenance and software upgrades. The Cisco ASR 1000 Series Router offers In Service Software Upgrade (ISSU) capabilities to allow a user to upgrade Cisco IOS XE Software while the system remains in service. This in service upgrade dramatically reduces downtime due to planned software upgrades and thereby increases service availability. (Note: One of the key original and ongoing design principles with the Cisco ASR 1000 is the criticality of ISSU and high availability.)


This white paper details the In Service Software Upgrade (ISSU) capabilities of the Cisco ASR 1000 Series Routers. This paper further examines the WAN Edge design and deployment options that can be employed to minimize service interruption during an in service upgrade or downgrade.


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