Cisco Catalyst 4500 Series Configuration Manual page 217

Chapter 5 Configuring the Cisco IOS In-Service Software Upgrade Process
After a switchover (NSF or SSO, not RPR), the standby supervisor engine takes over as the new active
supervisor engine (see
Figure 5-6
OL-25340-01
Figure 5-6).
Switch Over to Standby Supervisor Engine
Run new version
Cisco IOS Cisco IOS
12.x(y)S 12.x(y)S
Old
Active NSF/SSO NSF/SSO
Supervisor
Supervisor Switchover Switchover
Engine
Line cards
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
of Cisco IOS
on standby
Cisco IOS Cisco IOS
12.x(z)S 12.x(y)S
New
Active
Engine
About ISSU
5-9