Answer:
The ping command.
Step-by-step explanation:
In a network, workstations known as clients, users or nodes are the devices where data is needed or sents from. A server on the other hand, is a device in the network, configured to render a particular service like database, domain name service, web service etc.
When a link from a workstation to a server is down, the workstation looses connection the server. To confirm the connectivity of the link, "ping" the server ip address from the workstation using the command "ping 'server ip address'". This sends echo packets to the server, which is echoed back if there is connectivity.