Answer:
We use the Drainstop option
Explanation:
The admin can schedule a routine maintenance without taking the server offline and end up affecting user connections. He or she can do this by selecting the Drainstop option from the NLB manager and this service will be stopped temporarily. The Drainstop will first send a notification to the NLB cluster that a specific node will be temporarily stopped. Client connections and requests will still be active but will disable all new traffic coming in to the new host.