NETWARE 4.2 MIRRORING

We have 2 Novell Servers in our ofice at 2 departments with 10 clients each.Connection to the Servers by the clients are by hubs. Hubs are not connected to each other.Recently our office has completed Structured cabling .Consequently the clients are connected to the Servers by means of workgroup switches and these workgroup switches are connected to Layer 3 Switches (Core Switches) which in turn has connectivity to our various other branches of our company though VSAT.The problem is that when a client of a partiular Novell Server tries to connect to his department’s Server he finds that he is connected to the other department server. I am given to understand that this problem can be resolved by configuring VLANS but HOW DO I GO ABOUT IT.