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2 routers, 2 separate networks, 1 modem… how? (lemmy.ml)

submitted 10 months ago by [email protected] to c/[email protected]

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Hey all, I was wondering if anyone could help me work out how to do this? Basically, I have a stupid number of smart devices and my router has become increasingly unstable. I want to have all my IOT devices on one router and reserve the other for priority devices like phones and PCs.

I plan to put my IOT hub on 2G only and my primary hub on 6G and 6e only to avoid 2G congestion.

Problem is, if I connect both my routers to my modem, only one can connect to the internet. I tried putting a network switch between the routers and the modem, no dice.

Does anybody know how I can have 2 separate networks using 2 separate routers on a single modem? Both require internet connection but they don’t need to be able to communicate.

Thanks in advance for any help people can give :)

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[–] [email protected] 6 points 10 months ago (1 children)

Quick and dirty solution. Designate 1 as the primary, it gets the modem. The secondary gets plugged in, and appears as a single device to the primary. This works, but the secondary network is double NATed. This can make its internet connection a bit grumpy and laggy. It's fine for IoT devices however.

Best solution, upgrade to some more robust kit. I personally use the Ubiquiti Dream Machine. It's a massive step up from the cheap rubbish ISPs provide. It can do multiple vlans, and so separate the 2 networks, while sharing infrastructure. It also allows for things like remote management or VPN connections. It can be a good alternative for remote control, rather than exposing your master controller to incoming internet connections.

Also, what do you use as a master controller, and can it handle and internet dropout? I've known a couple of people burnt by their internet breaking, and taking their light switches with it! I personally use Home Assistant, but there are a few other options out there.

[–] [email protected] 4 points 10 months ago* (last edited 10 months ago) (1 children)

This works, but the secondary network is double NATed

Second one does not necessarily have to be double nat'd. You can disable nat, disable the internet port entirely, disable DHCP, DNS, and any other IP services on the secondary router, and just connect the switch of the secondary router to the switch of the primary router.

The second "router" no longer performs any routing or server functions. It just acts as an access point and a switch. When the IOT devices connect to the AP of the secondary router and request an IP address via DHCP, the request is fulfilled by the primary router's DHCP server.

Assuming OP's problem with excessive devices is a bug at the physical layer (SSID) and not at the link layer (MAC), this should resolve it. If it's at the IP layer or higher, it can't be solved with their current equipment.

Since the secondary router is neither handing out DHCP addresses nor requesting a DHCP address for its LAN interface, it will need a static address within the primary router's subnet for devices to be able to access it.

[–] [email protected] 1 points 10 months ago

Assuming the 2nd router is willing to play ball. I've seen some that won't go into access point mode.

Other than that though, it's another good option.