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Chapter 5 Configuring the Cisco IOS In-Service Software Upgrade Process About ISSU
An ISSU-capable switch consists of two supervisor engines (active and standby) and one or more line cards. Before initiating the ISSU process, copy the Cisco IOS software into the file systems of both supervisor engines (see Figure 5-4).
Note In the following figure, Cisco IOS 12.x(y)S represents the current version of Cisco IOS.
Figure 5-4 Install/Copy New Version of Cisco IOS Software on Both Supervisor Engines
Line cards
Active
Supervisor
Engine
Cisco IOS
12.x(y)S Cisco IOS
12.x(y)S
Cisco IOS
12.x(z)S
Cisco IOS
12.x(z)S
Cisco IOS
12.x(y)S
Install new version
of Cisco IOS
on active and standby
Supervisor Engines
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Cisco IOS
12.x(z)S
Cisco IOS
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Engine
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