Answer:
Drainstop
Explanation:
When the stop command is used through Network Load Balancing or NLB manager, it interrupts all client connection in progress on that server. However, the drainstop command does not interrupt any active connection on the server, but instead allow the host to service active connection, but ensures that all new traffic are disabled from the host or server. From the question, since the aim is not to interrupt the any clients currently being served by Server 1, the drainstop command is the ideal command.