I've been in a quandry to complete this networking task, but have gotten confused on how to create a subnet on an existing network. Resources available include a single IP 4-port router servng off of a T1 modem. Beind the router, one port goes off to one department, while another router port goes off to another department; each has their own hub systems serving their machines.
We are currently using local IP 192.168.1.1 (device IP) and 255.255.255.0 (subnet mask). Neither department is supposed to see or access each other. Unfortunately, both are currently being blinded from each other only by means of protocol settings, but, periodically the protocols are reset and each department can see each other until the protocols are reset. I need to stop this. First, the protocol method does not create any real security (obviously), and secondly, because these settings prevent either side from using the networks workgroup and sharing features adequitely.
First method: I have thought of using a hub to split the T1 feed then run two routers off the hub, each with their own global IP (I'd get a second IP from our ISP), then each department could keep their current local IP configuration without my needing to change anything.
Second method: I have also thought of trying to set up a subnet, but I can't quite figure out how to resolve the breakdown of how to reconfigure the subnet masks or how to confirm what local IP sets would be available. The existing router already has a menu for choosing 2, 4, and 6 subnet masks, but then I don't know what IPs would be available. I am also concerned that a subnet would not create the separation of the departments that I need.
Well, that's my quandry. I am looking for input as to the doability of my first method, or some direction for accomplishing the second method. No splitsies on this one. Best response get all the points.
Also, please, I am not a technician, so try not to use too much techspeak. You may give a great answer, but if I cannot decipher your remarks then it does me no good.