Sharing internet with second party in house

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New Around Here
Hi, I have FreshTomato 2020.6 running on my Netgear R6400v2 router. Everything runs fine for myself. But now I had some people moving into my house who would like to run their own router but use the same internet connection as me. Unfortunately the cable modem allows only one router to be attached since there is only one public ip address available for that.

Is there a way to share the internet with them, so that I can use my router as the main router which also manages the bandwidth that is shared? Ideally the networks should be separate and they should be able to manage their own port forwarding and so on. Is that even possible or do we need a second ip address?

Thanks, Mike


Very Senior Member
Depends on if you want to chance being held liable for their internet traffic.

if they go through your router, you will need to set up vlans to ensure that the two sub nets are isolated from each other. Basically, making them on a guest network.

Two routers in series will create double nat which may or may not be an issue by itself, but they will see a little extra latency.

cleanest solution would be to get them a separate IP address and put a small switch between the modem and the two routers if the modem does not have a switch built in. Otherwise, even a separate internet service would be simplest.


Very Senior Member
It depends primarily on your ISP modem/router. If it is a full standalone router, then your Netgear can plug in for your subnet and the new router can plug in for its own subnet. But if both subnets needs the same ports to be forwarded then you run into problems.

In a basic sense, connecting both routers to your ISP router works fine on a single IP (either direct if there are ports or through a switch). Also possible to cascade the routers giving you more control. Double nat is not an issue. I've run 3 or 4 layers for decades.

Once you get into the details though is were you'd have to decide if the configuration (port forwarding etc) will work in these cases and who is going to do all the "work" i.e. administer it all or are you giving them control or the the ISP box? Also, bandwidth management may come into play.


New Around Here
Thanks for the help and input. I didn't really think about the liability thing so far. Is there a way to reliably monitor all the traffic? So that you at least see who's accessing which IP's.

The cable modem only has one port and I don't have access to it. So using a switch and hooking up both routers to it would mean that I don't have control over the bandwidth or could possibly log what they would access, right?

I guess I would do it by cascading routers and log the IP's they access if that would help with liability. Or would be two seperate IP's be more save in that regard?

Is there a how to on how to properly setup cascading routers on Tomato?


Part of the Furniture
Using a switch would only work if you got/paid for 2 ISP services. The provider would switch out the modem you have now anyway if you went that route (highly recommended).

With their own ISP service, you're not responsible for anything (even the payment of the service).

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