The correct sequence for mounting a Cisco device in a rack is:​

Install mounting brackets: Attach the appropriate rack-mount brackets to the sides of the device using the screws provided. This step prepares the device for secure installation in the rack.​

Mount in rack: Carefully place the device into the rack, aligning the brackets with the rack posts, and secure it using the appropriate rack-mount screws.​

Ground the device: After the device is securely mounted, connect the grounding wire to the chassis grounding point and then to the facility ground. This step ensures safety and compliance with electrical standards.​

This sequence is recommended to ensure both the physical security of the device and the safety of personnel during installation.​