Why is my router's default gateway changing?

Question

So I have a router connected to my main modem downstairs through a LAN cable, via the LAN ports on both routers. My routers default gateway is usually 192.168.1.1, and my modem's gateway is 192.168.18.1. But for some reason whenever I restart my router, my routers gateway is set to my modems gateway... I can't access my routers gateway, I can only access my modem's gateway. But after like a day or so, it changes again and my routers gateway is set back to 192.168.1.1. Why is this happening?

Also, if its possible, I want to change my routers gateway to my modems gateway, because my router blocks a lot of websites unnecessarily. Basically I want both my modem and router to have the same gateway 192.168.18.1. How would one go about doing that?

@user1686 I can access this gateway because like I said, after a day it changes back to its default gateway. This is my routers gateway because it says this gateway on the back of the router. Also I highly doubt it has anything to do with my computer because the random website blocking on the default gateway happens on every device connected, not just my computer.

@harrymc I actually have no idea, I just learnt what a DHCP server is... so I should disable DHCP server on my router right?

Answer 1

It sounds like you're saying that your computer is showing either the router or the modem as the computer's configured gateway, randomly switching between the two.

This usually happens because you have both devices working as DHCP servers on the same network – i.e. it sounds like you've connected the router using its LAN port to the network, and its default configuration is not designed for that.

In short, both your modem and your new router are answering the computer's DHCP "lease request" packets, and the computer picks up whichever offer happens to arrive first.

Also, if its possible, I want to change my routers gateway to my modems gateway, because my router blocks a lot of websites unnecessarily. Basically I want both my modem and router to have the same gateway 192.168.18.1. How would one go about doing that?

The first step is to bypass the router's "router" as such, e.g. by connecting it through the 'LAN' port (instead of the 'WAN' port) to the modem. It sounds like you already have this, because it's what's causing you the problem with gateways (due to incomplete setup), but at the same time it is actually what you want if you want to create a single network.

The second step, importantly, is to connect to your router and turn off its "DHCP server" feature (and UPnP while you're at it), so that it will not attempt to advertise itself as a gateway – it will only work as a bridge, which is what you're asking for.

Answer 2

You should have just connected your modem to your router through the "WAN" port and everything would have worked fine, that is a better solution, like this, every of the devices that you will connect to your router will get their IP addresses through the router dhcp and all the traffic will go to your modem through the router. Because the router has two interfaces one that connect the devices between them and one other to the modem, and that second interface get its IP adress by the modem. check this out .I think its too late but think that might help someone else

computer-router-modem connection