In a Cisco Catalyst 6500 Series Switch with redundant supervisors, how is the Cisco IOS image upgraded?
A. The active supervisor automatically synchronizes the image to the standby supervisor.
B. The standby supervisor is removed and reinstalled in the chassis to synchronize images.
C. The line cards in the chassis are reloaded upon supervisor switchover.
D. SSO is used to automatically synchronize images between the active and standby supervisors.
In a Nexus 7000 series chassis with dual supervisors, you can use the in-service software upgrade (ISSU) feature to upgrade the system software while the system continues to forward traffic. An ISSU uses the existing features of nonstop forwarding (NSF) with stateful switchover (SSO) to perform the software upgrade with no system downtime.
In a redundant system with two supervisors, one of the supervisors is active while the other operates in the standby mode. During an ISSU, the new software is loaded onto the standby supervisor while the active supervisor continues to operate using the old software. As part of the upgrade, a switchover occurs between the active and standby supervisors, and the standby supervisor becomes active and begins running the new software. After the switchover, the new software is loaded onto the (formerly active) standby supervisor.
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/high_availability/configuration/guide/ha_issu.html