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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
Configuring a VSS
Note After you confirm the command (by entering yes at the prompt), the running configuration is 
automatically saved as the startup configuration and the switch reboots. After the reboot, the switch is 
in virtual switch mode, so you must specify interfaces with three identifiers (switch/module/port).
When switches are being converted to VSS, you should not set them to ignore startup-config. If done, 
the switch can be enabled to parse the startup-config at the rommon prompt. Ignoring startup-config in 
VSS mode, causes a switch to boot in a semi-VSS mode, which can only be corrected by a reboot and 
by enabling the parsing of startup-config.
Converting to Quad-Supervisor VSS
You can convert to Quad-Supervisor VSS mode using one of the following ways:
• Converting an Existing VSS Switch to Quad-Supervisor VSS Mode
• Converting a Standalone Switch to Quad-Supervisor VSS, page 5-37
Converting an Existing VSS Switch to Quad-Supervisor VSS Mode
To convert to Quad-Supervisor VSS from an existing VSS setup, perform the following task:
Step 1 Perform an ISSU or a switch reload, to upgrade the chassis active supervisors with the Cisco IOS XE 
image that supports Quad-Supervisor VSS mode. Ensure that the switch reaches Stateful Switchover 
(SSO) in the VSS. The BOOT variable must point to the path of the Cisco IOS XE image and must be 
saved in the startup configuration. For more information about ISSU upgrade, see In-Service Software 
Upgrade (ISSU) on a VSS, page 5-56.
Step 2 Insert the redundant supervisors in the appropriate slots. Configure ROM monitor to auto-boot on the 
standby supervisors of both the VSS Active and the VSS Standby switches, using config register. Load 
the Cisco IOS XE image on both the standby supervisors and ensure that both supervisors are brought 
up in RPR mode as in-chassis standby (ICS) supervisors. The in-chassis active supervisor then syncs its 
startup configuration to the ICS.
Step 3 Copy the Cisco IOS XE image on the standby supervisors of both the switches, from the VSS Active 
switch console, using the IOS copy command so that the boot variable has a valid path to point to
The ICS bootflash filesystem is mounted with the name 
bootflash-ics:. On the VSS Active switch, the 
ICS bootflash filesystem of the VSS standby switch is available as 
slavebootflash-ics:.
Converting a Standalone Switch to Quad-Supervisor VSS 
To convert a standalone switch to Quad-Supervisor VSS mode, perform the following task:
Command Purpose
Switch# copy bootflash: <image_name> bootflash-ics: 
<image_name>
Copies the image from the VSS Active switch to the 
ICS bootflash system of the VSS Active. 
Switch# copy bootflash: <image_name> slavebootflash- 
ics: <image_name>
Copies the image from the VSS Active switch to the 
ICS bootflash system of the in-chassis standby 
supervisor.