Cisco Cisco IOS Software Release 12.2(33)SRE

This section describes prerequisites for performing ISSU.

Ensure that both the active and the standby Route Processors (RPs) are available in the system. 

The new and old Cisco IOS software images must be loaded into the file systems of both the active 
and standby RPs before you begin the ISSU process. 

Stateful Switchover (SSO) must be configured and working properly. If you do not have SSO 
enabled, see the Stateful Switchover document for further information on how to enable and 
configure SSO.

Nonstop Forwarding (NSF) must be configured and working properly. If you do not have NSF 
enabled, see the Cisco Nonstop Forwarding document for further information on how to enable and 
configure SSO.

This section describes restrictions for performing ISSU. 

Before you perform ISSU, ensure the system is configured for redundancy mode SSO and that the 
file system for both the active and standby RPs contains the new ISSU-compatible image. The 
current version running in the system must also support ISSU. You can issue various commands to 
determine RP versioning and compatibility, or you can use the ISSU application on Cisco Feature 
Navigator.

Do not make any hardware changes while performing an ISSU process.

ISSU is available only in Cisco IOS 12.2(28)SB software released for the and later.