It is a common practice to physically cable the monitoring ports, only after the Sensor has been fully configured.
In other words, most administrators cable the console and management ports, use those connections to configure the solution, and physically introduce the Sensor into the scanning process once the proper scanning policies are in place, the monitoring ports have been configured, the latest signature set has been downloaded, and so on.
Additionally, in the most security-conscious environments, or those with congestion problems, a private network is often used to connect the Sensor management ports to the Manager. This is another best practice in terms of cabling the Sensors.