What about vlans? You could put a router (or a layer 3 switch) where your server is located and then connect your server pc directly to that router. Assign that a subnet or a vlan, say vlan 10 and then assign your other two groups a vlan (or separate vlans like 20 and 30 for example). Or like I said you could use subnets.
Since each subnet is a different network, you would have to have a router (or layer 3 switch) to route the packets between each network or subnet. I will attach a drawing.
Subnet like this:
Yeah, I know my paint skills are atrocious...
Edit: Either way, you must have a router (or layer 3 switch) if you plan on connecting multiple separate networks or vlans. A switch will not cross networks, only a router will. Even if they are all connected to the same switch and the separate vlans are all on the one switch, they will not be able to communicate without a router or layer 3 switch (which is basically a router). The above setup will be optimal and you should get fantastic speeds because of the micro segmentation from switched networks.
Every device connected to your switches has its own collision domain, meaning you will not have any collisions which gives you the best performance. I'm assuming you're going to be using 100 Mb/s ports on your switches which should be ample, however you can get gigabit or even 10 gigabit ports (if you have the money).
2nd Edit: I left out the internet connection. You could simply connect Router1 to the internet or you could add another router to the 10.1.2.0/24 network and connect that one to the internet, kinda like you have yours set up above, though you have a switch connecting you to the internet which wouldn't work, you'd need a router.
I hope this helps. If you have any more questions, please post them below. If this answers your question, select best answer. Thank you.
Thanks heaps so far. I have a Cisco 881 Router that I can use.
At the moment I have a substantial wan network setup on the left side using the ip range 10.7.203.x which is all managed by our isp to connect 15 subnets (10.7.201.x, - 10.7.215.x).
The right hand side is setup with a different ISP that allows larger traffic usage due to the requirements of the office. However we do not want to use Internet or manually connect drives. the office currently uses the ip rang 10.1.1.x
So far I have understood that all 3 will need their own ip range.
Office network 10.7.203.x (as this is where in the wan it will be connected) - Allocated by edgerouter/isp wan setup
Server PC 10.1.2.x - allocated by center router? or static?
Design office 10.1.1.x - allocated by internet router on right hand side
What other settings will I need to change in the router to get this working?