How to connect ONT to a non-ISP provided router?

Question

My final objective is to load balance the internet signal from two different ISPs and distribute that through a mesh network.

My initial setup was the following. I have a cable modem from which I receive the signal from the first ISP. The signal comes from a coaxial cable coming from the street.

The modem first connects to a router, which I recently added because I needed more LAN ports. Let's call it router 1. I have disabled the WiFi from this router.

Router 1 has two desktop computers connected to it and a WiFi mesh router (tp-link Deco E4).

Now the second ISP has been installed. I now have an ONT right in my bedroom which connects to the optical fiber cable that comes from the street. This ONT has been homologated by the ISP, which is a local Brazilian company. It's not a commercial model.

The second ISP also added another router. Let's call it router 2. This router has been set up with WiFi.

Now, before the load balancer arrived, I did some tests. I found it weird that, if I connect a computer directly to the ONT, I can't connect to the internet. However, if I connect directly to the cable modem, I can connect to the internet.

The same thing happens if I connect router 1 to the ONT. It seems that only router 2 is capable of connecting to the internet by connecting to the ONT. Seems to me like the ONT is set up in such a way as to only provide connection to the internet if the router is set up in a specific way.

Now the router with load balancer arrived (tp-link ER605). Let's call it router 3. The idea is to replace router 1 with router 3, but use both the cable modem and the ONT on the WANs. Did some tests and router 3 failed to connect to the ONT.

Then I had an idea. I connected a computer to the ONT and, on Windows, ran ipconfig. I got an IP of 169.254.*.* and mask 255.255.0.0. So I set up the router 3 to static IP, punched those numbers and it managed to connect. However, I still can't access the internet from it. If I disconnect the ONT WAN I can access the internet through the signal from the cable modem WAN. But if I disconnect the cable modem and connect the ONT, even though router 3 says it's connected, I can't access the internet.

Even though I'm a computer engineer my knowledge of networking is limited. So, what can I do to achieve what I want? Just to remind you, this is what I want: router 3 receiving a signal from the cable modem and the ONT and distributing that signal to two desktop computers and the WiFi mesh router.

Answer 1

I connected a computer to the ONT and, on Windows, ran ipconfig. I got an IP of 169.254.. and mask 255.255.0.0. So I set up the router 3 to static IP, punched those numbers and it managed to connect. However, I still can't access the internet from it.

"Managed to connect" doesn't tell you anything. There is no actual connection procedure if you've configured a static IP address – the router doesn't know whether it's "connected" or not. It just sends packets and receives packets back (or doesn't). So it's not useful to do this at all (as opposed to using DHCP autoconfiguration).

There can be several reasons why the router cannot get an address through DHCP:

1. The ISP may be only allowing a specific MAC address to request a DHCP lease. (Try configuring the new router's WAN interface to "clone" the old router's... keep in mind it'll be a different MAC address than the one on the "LAN" side.)

2. The ISP may be expecting a specific option (e.g. a custom "user class") in the DHCP request.

3. The connection may require a VLAN tag. (VLANs are used for multiplexing several networks over the same link, e.g. an "Internet" VLAN and an "IPTV" VLAN; the "tag" would indicate the VLAN ID 1-4094.)

4. The connection may require 802.1X authentication. This is an annoying one, as it might require some way to extract the password or even a certificate from the old router.

5. The connection may require PPPoE. Depending on ISP this might also require a username and password, or it might not.

I would find a computer with two Ethernet ports (or a switch with a "port mirroring" capability), configure it as an Ethernet bridge between the two ports, connect one port to the ONT and another to the ISP-provided router. A packet capture would show whether the router is doing anything special to obtain a connection.