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
Dual-active fast-hello link counters:
Tx Rx
Port OK OK
--------------------------------------
Gi1/1/5 762 759
This example shows how to display the status of total packets exchanged between the fast-hello links on
the VSS:
Switch# show switch virtual dual-active fast-hello packet
Executing the command on VSS member switch role = VSS Active, id = 2
Dual-active fast-hello packet counters:
SwitchId : 2
Transmitted:
total = 465
Received:
total = 465
Executing the command on VSS member switch role = VSS Standby, id = 1
Dual-active fast-hello packet counters:
SwitchId : 1
Transmitted:
total = 465
Received:
total = 465
In-Service Software Upgrade (ISSU) on a VSS
Topics include
•
VSS ISSU Concept, page 5-56
• Traffic and Network Protocol Disruption During ISSU in a VSS, page 5-57
•
Related Documents, page 5-58
• Prerequisites to Performing ISSU, page 5-58
•
About Performing ISSU, page 5-59
• How to Perform the ISSU Process, page 5-64
•
License installation and subsequent VSS formation are now complete., page 5-85
VSS ISSU Concept
In a VSS, the supervisor engines on the peer switches maintain an SSO (stateful switchover) relationship
between themselves. This facilitates the ability to perform a software upgrade (or downgrade) on both
the VSS supervisor engines.
Figure 5-9 below depicts (at a conceptual level) the sequence of events that take place when the VSS
system is upgraded from software version X to version Y.