Drop-in Gateway - Subnet

I have a modem/router combo assigned 192.168.1.1 and then I have a Flint 2 assigned 192.168.8.1. I have an ethernet cable connected from the LAN port of the modem/router combo to the WAN port of the Flint 2. My goal is to have DHCP turned off on the modem router/combo and use DHCP from the Flint 2 while:

  1. Assigning all clients an IP in the 192.168.8.X subnet
  2. Still be able to get out to the internet

I know I can (and have tested) using the Drop-in Gateway feature but that assigns clients of the modem/router combo an IP in the 192.168.1.X subnet. If I change the IP of the modem/router combo to for example 192.168.8.2 then I have the problem that the WAN and LAN are on the same subnet.

Is there a way to achieve this without additional hardware?

Several ways:

  1. Passthrough
    The correct way is to set up your modem/router combo in passthrough mode. Of course if this mode may not be avaiable.

  2. Double NAT
    Just keep your connect as is and all of your devices should connectg to Flint 2. So you will only use 192.168.8.1/24 subnet. You will have double NAT but most of the time this is not a problem.

  3. Drop-in gateway
    You have tried this mode but you need to turn the DHCP server on your modem/router OFF. In this case, all of your devices will get 192.168.8.x IP even if they connect to your modem/router directly.

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@alzhao thank you for the reply.

I still want to be able to connect some clients through the modem/router combo for the increased wifi coverage. It and my Flint 2 are on different floors.

Using Drop-in Gateway, clients connected through the modem/router combo do not get a 192.168.8.X IP. They end up on the 192.168.1.X subnet. I know you said otherwise but that’s not what happened for me, maybe you could double-check that.

As far as features of the modem/router combo, it can operate in tagged or untagged mode and can set static routes.

Thinking out loud, how can I have clients of the modem/router combo get addresses in 192.168.8.X when the LAN of the modem/router combo itself is 192.168.1.X? Do I somehow need to configure the port of the Flint 2 to act as both a WAN/LAN port at the same time? If I change the modem/router combo to be 192.168.8.2, it has DHCP turned off, the Flint 2 handles DHCP requests, but I’m plugged into the WAN port of the Flint 2, it’s going to give an error that the WAN and LAN are on the same subnet. Is there a way around that?

sorry, I was wrong.

Can we come to the beginning: Why do yo uwant to use the Flint 2 router?

Do you want it to extend your current network or do you want to use vpn, adguard home etc?

If you want to extend your current network only, you should set up as AP or Extender.

If you want to use vpn, adguard etc. you can use as Drop-in gateway, but all the devices should keep your current subnet, i.e. 192.168.1.x.

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I was hoping to use the Flint 2 for both the VPN and to extend my network. Furthermore the reason I’m trying to get all clients on the same subnet is because I would like autodiscovery services such as for Spotify finding home speakers, Plex finding local servers, and other smart home devices to be able to scan and pick up the devices on the network regardless of which router they’re connected through.

The problem seems to be that to put all clients on the same subnet would mean having the LAN and WAN be on the same subnet which doesn’t work. Unless I’m missing something. Is there a way or is it somehow possible to have clients connected to the modem/router combo be assigned a 192.168.8.X IP while using for example 192.168.1.2 as their gateway (WAN IP of the Flint 2) such that the IP and gateway are different subnets but it routes correctly because the Flint 2 can see both subnets? Is this where a static route needs to be added to the modem/router combo?

Instead of plugging from a LAN port of the modem/router combo to the WAN port of the Flint 2, is there a way I could do this by plugging into a lan port of the Flint 2? Thinking through that, the Flint 2 would be on the 192.168.1.X subnet. Suppose the modem/combo router gets 192.168.1.1 and the Flint 2 gets 192.168.1.2. The Flint 2 would act as the DHCP server and the gateway. But then there would be no WAN for the Flint 2? Traffic would come to the Flint 2 on 192.168.1.2 as the gateway but then how would it route to 192.168.1.1 after to get internet access?

This should be possible. You want to use Flint 2 as bridge, vpn and drop in gateway. Unfortunately this needs some manual config and not available directly from the UI.

Maybe just use two routers.

Agreed, using two routers is by all means the easiest option. This was partly a learning endeavor to be honest. Suppose I was to keep pursuing it, what direction might you point me in? Using the luci interface or ssh? I’m leaning towards the most practical way would be connecting to a LAN port of the Flint 2 and then somehow adding a route to point outbound traffic to the modem/router combo gateway after it has been processed by the Flint 2 (such as after the VPN). I’m not experienced enough to know what that setup/command would look like, if it’s something like forward traffic destined for 0.0.0.0 to the modem/router combo’s 192.168.1.1 for example.

Not so sure exactly what you mean but my suggestions:

  1. If you want to use vpn, just use the Flint 2 in default router mode and connect all the devices that need to use vpn to Flint 2. Don’t think about the same subnet as your modem/router combo.

  2. If you want to extend the network, use Flint 2 in bridge mode. Don’t think about vpn.

Other mode, e.g. Drop-in gateway mode, works for vpn but may not be that reliable and may have leaks. Unless you are ok with that, don’t use that mode.

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