Cisco Catalyst 4500 Series, Software Configuration Manual

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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.0E and IOS 15.2(5)E
Chapter 7 Configuring the Cisco IOS In-Service Software Upgrade Process
About ISSU
Figure 7-8 Steps During the ISSU Process
Performing an ISSU Upgrade: 2 Methods
There are two ways to perform an ISSU upgrade: manually, with four commands; or automatically, with
one command.
The normal ISSU upgrade process involves issuing four separate ISSU exec commands
(
issu loadversion , issu runversion , issu acceptversion , issue commitversion ) along with additional
show command invocations to evaluate the success of each command before proceeding. Although the
ISSU process is complicated, you should not expect disruption of service. The use of multiple ISSU
commands dictates an additional level of care to ensure no service disruption. However, in some
scenarios, this upgrade procedure might be cumbersome and of minimal value. A typical example is
during a network upgrade that involves performing an ISSU upgrade on a large number of Catalyst 4500
switches. In these cases, we recommend that you first perform the normal (four command) ISSU upgrade
procedure on one switch (possibly in a lab environment) to verify successful upgrade. Then, use a single
issu changeversion command to perform an automatic ISSU on the rest of the Catalyst 4500 switches
in the network.
Note To use the issu changeversion command, both old and new IOS versions must support issu
changeversion functionary.
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5
Standby
New
Active
New
2
Standby
New
Active
Old
* Acceptversion
Abortversion
Abortversion
Switchover
4
Standby
Old
Active
New
3
Standby
Old
Active
New
Commitversion
Runversion
Loadversion
Commitversion
Commitversion
Commitversion
Runversion
Loadversion
1
Standby
Old
Active
Old
* This command is optional.