Question Connecting two completely independent networks through one modem

Aug 20, 2020

This is for home use. I want to create two completely independent wireless/wired networks that are both connected to the internet through one modem. The gear I am using are Netgear model R7000 and R7800 routers, and a Spectrum cable modem.

One of the networks is for my wife's business, and the other is for general household use. I want these two networks isolated to the point that if I'm working on the home network and shut the power off to the router, the disturbance won't interrupt my wife's video conference calls on the other network. We don't want these two networks to interact at all or share anything. I think that I need to use a switch to act as a gateway between both routers and the modem, but I don't know what kind of switch is needed to do this well, or how to set it up correctly. Does anyone know how to do this the best way?

Thank you for any help
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I can think about two options, there may be several other means of solving the problem:
  • Replace your modem to a model that support separate guest network.
  • Maybe your wife can use VPN. But I don't know if that alone make it any secure for potential threats from within the same network. Some other with experience about VPN may tell if it's a workable solution or not.
You could just hook 2 different router to the "modem" BUT if the device actually is only a modem the ISP will not allow it. They only give you a single IP addresses and they will almost never allow you to hook 2 modems to the same house even if you were to pay for 2 accounts. You can call them and see if they have any options. A second public ip if they offer it will be the cheapest, the next is to buy a second internet account in your house and place a second modem in connected to the same coax.

If the device is actually a modem/router combo box then you can just place 2 routers behind it one for each network. Since these router think the wan interface is internet they will prevent any traffic from coming in form the other router as well as any actual internet traffic.
So the simplest and cleanest way is to get a second IP address from your isp and then use a switch for the two router wan ports. Unfortunately, most isps don't offer more than one public ip per modem on residential connections.

So you could get a business account ($$), get another modem and connection ($$), or you could do something much more simple, but that comes with the caveat of double nat--add another router.

You can put a router in front of both routers just to give each router it's own ip. This would be a private subnet. Then each of the two routers would have its own private subnet, which ideally will not be one of the others. So you'll probably be using all three private ranges--10.x.x.x, 192.168.x.x, and 172.16.x.x.

Because you'll have two nats to go through, wife's work may have some issues if she's using vpn clients. One way around that would be to use the dmz on the first line router for her work router to potentially eliminate any nat issues.

I applaud you for separating your work and home networks this way--this is really the way it should be done imo--no connection whatsoever.