Cisco Catalyst 4500 Series Software Configuration Manual page 407

Chapter 8 Configuring the Cisco IOS XE In Service Software Upgrade Process
After you have copied the Cisco IOS XE software to both file systems, load the new version of
Cisco IOS XE software onto the standby supervisor engine (see
Without the ISSU feature, SSO/NSF cannot function between the active and standby supervisor engines
Note
when they are running different versions of the Cisco IOS XE image.
Figure 8-5
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Load New Version of Cisco IOS XE Software on the Standby Supervisor Engine
Load new version
of Cisco IOS XE
Cisco IOS XE Cisco IOS XE Cisco IOS XE
3.x.y.SG 3.x.y.SG 3.x.y.SG
Cisco IOS XE Cisco IOS XE Cisco IOS XE
3.z.y.SG 3.z.y.SG 3.z.y.SG
Active
NSF/SSO
Supervisor Supervisor
Engine
Line cards
Figure
on standby
Cisco IOS XE Cisco IOS XE Cisco IOS XE
3.z.y.SG 3.z.y.SG 3.z.y.SG
Standby
Engine
About Performing ISSU
8-5).
8-9