An engineer plans a Cisco ACI firmware upgrade. The ACI fabric consists of three Cisco APIC controllers, two spine switches, and four leaf switches. Two leaf switches have 1-Gb copper ports for bare m

This option is textually identical to C, which describes the correct first step in an ACI upgrade for minimal disruption.

Upgrading APICs using the 'most recent' firmware is not always the correct approach; the engineer must select the specific 'desired' and validated firmware version for the deployment.

For minimal disruption during an ACI firmware upgrade, the APIC controllers are upgraded first, typically one by one in a cluster while maintaining quorum, by selecting the desired firmware and initiating the process. This ensures the control plane remains operational during the upgrade of the APICs before proceeding to spine and leaf switches.

Upgrading APIC controllers as a 'single group' would involve upgrading them simultaneously, leading to a loss of quorum and control plane functionality, causing significant disruption.