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Layman here. Let’s say I have access to a school dorm room Ethernet network, but can only have one direct connection to the network (e.g, if I connect a laptop and a game console to different Ethernet ports, either the laptop or the game console will have Internet, but not both). So, I want to use a router. Can I configure it so that it creates a network where:

  1. It freely assigns IP addresses to computers connected to that network without affecting computers connected to the school network
  2. The computers on my network are isolated from the rest of the computers?
Giacomo1968
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3 Answers3

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Yes. This is precisely what almost all consumer-grade routers do by default when you connect a wired network to their WAN port.

David Schwartz
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Yes, this is analogous to connecting a home network to the Internet. The Internet has no visibility of the structure of the internal network, it just sees the requests and responses that come from it.

So in this case, you would connect a router to the ethernet port. You will need one that has a WAN port. This is connected to the dorm room port, and the WAN port get's its IP address from the school network. Your devices connect to the LAN ports and Wifi of the router, and are provided their IP addresses by a DHCP service on the router.

Connections from your devices will go through the router, and be “hidden” using NAT behind the IP address that the school network gave the router.

If you get a domestic router, these will usually work this way out of the box.

Giacomo1968
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Paul
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Is it technically possible, on most consumer-grade routers, to create a subnetwork that does not affect the operation of a larger network?

Yes, as others point out this his how pretty much every router in the world works whether they be small scale consumer level routers or larger scale Enterprise routers.

The way it works is simple:

  1. WAN Connection: Your dorm room’s Ethernet jack that connects to the school network can be consider the WAN connection. If you take that Ethernet cable and connect it to your PC you would get a direct connection to the school network. But since this is one Ethernet connection, you will only be able to connect one physical device to the network and then—depending on school network settings—you will only be assigned one IP address. This is quite restricting.

  2. Using a Router for NAT (Network Address Translation): The main benefit of a router is for NAT (Network Address Translation) functionality. In layman’s terms, NAT functionality does exactly what your question describes: It creates an isolated subnetworked LAN that then allows you to communicate with the larger school network’s WAN connection without having to acquire more than one IP address from the larger school network’s WAN. Most basic routers have at least 3-4 wired Ethernet LAN ports for this purpose.

  3. Using a Router for DHCP (Dynamic Host Configuration Protocol) in addition to NAT: While NAT is the main benefit of using a router, DHCP (Dynamic Host Configuration Protocol) is used on most all routers—even the cheapest consumer level routers—to make basic device network configuration setup easier to deal with. A DHCP server on a router allows network devices to simply be “plug and play” as far as getting an assigned network address, gateway address and other sundry info goes.

Now that all said, this oversimplifies things. In an ideal situation your school will allow you to use a wired router for the purposes described above and in your question. But some schools might have their own rules that would effectively block the use of routers for various reasons.

So while some will say hooking up a router to your dorm is just as easy as using one in the home, remember: Your school is not an ISP (Internet service provider) and has no real obligation to make accommodation for personal routers if they don’t feel they have to support such a setup.

So it’s best to be honest/legit and contact your school’s department of information technology to see if they are fine with you setting up a personal router on your dorm connection. Heck, they might even have a list of recommended routers you can use so that makes things easier.

Giacomo1968
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