Cisco Catalyst 4500 Series Software Configuration Manual page 286

In-Service Software Upgrade (ISSU) on a VSS
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ISSU using the four-command sequence
The manual ISSU upgrade process involves issuing four distinct ISSU EXEC commands in sequence
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A fifth command, issu abortversion, enables you to abort the ISSU upgrade process at any time, and to
revert to the initial system state.
These four commands take the VSS through a series of states that culminate in the Active and standby
supervisor engines running the post-upgrade IOS XE image. The VSS continues to operate throughout
the entire process; however as explained in
VSS, page
switch that is undergoing a reboot.
Figure 5-11
the sequence of four commands entered. It also shows the effect of the issu abortversion command at
any given point during the process.
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
5-60
manually using a sequence of four commands
automatically; using a single command
issu loadversion
issu runversion
issu acceptversion
issu commitversion
5-57, service is disrupted on network links that terminate on interfaces that reside in the
depicts the states through which the VSS Active and standby supervisor engines progress as
Chapter 5
Traffic and Network Protocol Disruption During ISSU in a
Configuring Virtual Switching Systems