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.xE and IOS 15.2(5)Ex
Chapter 5 Configuring Virtual Switching Systems
In-Service Software Upgrade (ISSU) on a VSS
•
manually using a sequence of four commands
• automatically; using a single command
ISSU using the four-command sequence
The manual ISSU upgrade process involves issuing four distinct ISSU EXEC commands in sequence
•
issu loadversion
•
issu runversion
•
issu acceptversion
• issu commitversion
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
Traffic and Network Protocol Disruption During ISSU in a
VSS, page 5-57 , service is disrupted on network links that terminate on interfaces that reside in the
switch that is undergoing a reboot.
Figure 5-11 depicts the states through which the VSS Active and standby supervisor engines progress as
the sequence of four commands entered. It also shows the effect of the issu abortversion command at
any given point during the process.