EggXpert

I am trying to plan out a network setup, that will let me use my primary work desktop in a separate network from a test network that will contain servers in a domain with test machines.

I’m in a dorm with one Ethernet jack that gets assigned 1 IP from the university. Right now I just have a basic consumer type dlink router connected to it, and then my primary desktop is connected to that, and a laptop is connected wirelessly.

I’m wondering if I got another router, and connected it’s wan port to a regular port on my main router, if that would let me create a 2^nd separate network, that I could then create a actual domain with test servers, and a separate IP structure that would not conflict or even be able to directly access my primary desktop PC. This is graphically what I am thinking:

One basic issue I see is that your two routers both share the same IP address and will cause a conflict on the network.  What you may have to do is have your test network as a standalone network to keep it separate from your main desktop.  The reason I think you will need to go that route is that most likely, you are going to have to disable DHCP on your secondary router in order for it to get an IP address from the primary router in order to avoid the address conflict.  In addition, if you plan to set up the server as a domain controller, the server will be providing the IP addresses on the test network.  This will also cause an IP address conflict between the routers and the domain controller on the server. 

I may not be 100% accurate on my info as it has been a few years since I took Network+ but I do know that you will have issues trying to set up the network the way you have it graphed out.  Hopefully, one of the more network config savvy Eggxperts will add better information that either corrects my information or clarifies more detail on why it won't work the way you would like to configure the networks.

The way you have your network drawn out will never work.  Routers are layer 3 devices.  As such traffic moves from one interface to another when a route must be performed due to traffic going from one network/subnet to another.

As pointed out by Tekran, you have a number of issues here.  First you have duplicate IPs across your network design all sitting on probably the same class C subnet.  You have to come up with a different IP address scheme to make any network communication work.

Next, your requirement that your test network not have access to your main desktop will not work here either.  The assumption is you will be using standard consumer grade routers.  If you are using standard consumer grade routers, you will need to reverse how you physically wire up the network devices.  You need to have your desktop sitting on the second router for your test network in your diagram and your test network devices will need to move to where the first router is.