Multi Port Router
 

I want to share a single DSL to 5 diffrent departmnets of the office and each one should be able to share their own files and every department should be on a diffrent network address for security
e.g. DEp1 is at 192.168.0.1
DEP2 is at 192.168.1.1
DEP3 is at 192.168.2.1
and all the department should have access to internet from a single source (DSL)
Now how can we setup a Multi Port Router in a single PC with 6 NIC 1 for WAN and 5 for LAN or can it be Alias on just 2 NIC 1 for WAN and other one To be Alias for 5 department.