This is a tough answer, as the details are a bit thin. A diagram of the network would help.
However, in the clearest sense from what you posted, if the server and the workstation (PC) are on the same network, and are in the same VLAN, they will share the same router. Conversations between the workstation and the server will traverse the local VLAN and not touch the router except at the start of a conversation when a workstation will broadcast an ARP request for the server. Conversations to workstations outside of the local VLAN (network/switch/hub) will go through the router to the other network location.
Conversely, a router has little to no need of talking *to* a server, unless there is a forward rule such as a internal web server that is reachable from the Internet.
TankII