How to use multiple routers with fibre optics cable?

Question

I am not very experienced with optic fibre installations, so bear with me if I get something wrong.

Assume you have house with direct access to an optic fibre cable (FTTP). In the basement, there is the ONT+residental gateway device that converts the light impulses to Ethernet. At the moment, a router is directly connected to this device.

This setup has to be changed because the house will be split into 2 apartments. As I have to assume that every household will bring its own router of their ISP of choice, I have to do something else instead of connectimg a router to the ONT/RG box.

How can I do this, so that the 2 parties can use their own router? Until now, I've always had DSL routers connected to telephone jacks of each apartment. I am looking for the equivalent for fibre optics.

Answer 1

You need to purchase at least two external IP addresses. Normally the IP blocks start at 6 addresses.

Then you can install a very good small and very fast switch at the "entrance" of the fiber connection. That would be the ISP Modem or device they use to give you the signal.

Now a regular (fast) Router can be attached to one switch port and another such Router to another switch port.

Now each apartment has their own router and connection.

That should work well and how we hook up some small businesses.

Your 2 DSL connections amounted to basically the same as above.

Answer 2

Intro:

I'll first answer the question you asked, and then answer the question you probably wanted to ask ;-)

Connecting (2) Routers with Single Internet Connection:

This is dead easy and you don't need any other public IPs. Note that this solution works independent of what type of Internet connection you have: Could be ADSL, VDSL (FTTC) or as in this case FTTP (Full-Fibre).

The router connected to the ONT will be your Internet gateway router for itself and the other router, we'll call "Router 2" for the example.

Example's IP addressing:

• Internet GW Router uses 192.168.1.0/24 to assign addresses to WiFi clients
• Router 2 uses 192.168.2.0/24 to assign addresses to it's WiFi clients
• The Point-To-Point links connecting the (2) routers will be 192.168.3.0/30 in the example.

P-T-P links (a /30 mask) are used to route traffic between routers, not to assign addresses to hosts and should be from a completely different subnet than the traffic routed across these links. P-T-P links are not random IP addresses but the product of IP Calculations

Internet GW Router Config:

Using a subnet calculator to identify two /30 Point-To-Point IP addresses, we enter:

192.168.3.0/30

which returns (2) IP addresses:

192.168.3.1
192.168.3.2

Since the cable to the ONT will be in Port 1, create an interface for 192.168.3.1 on Port 2 if it's free.

Plug an Ethernet cable into this new interface created for Port 2.

Router 2:

Plug the other end of the Ethernet cable from the Internet GW Router into Router 2 on Port 2 also if it's free.

Create an interface for the remaining P-T-P address 192.168.3.2 on the interface you connected the Ethernet cable on Router 2.

Next, set the default route on Router 2 to the Internet GW Router's P-T-P address 192.168.3.1. Now any traffic not meant for 192.168.2.0/24 will squirt out the default GW.

Finishing Up:

Masquerade Router 2's traffic for subnet 192.168.2.0/24 on the Internet GW Router.

The Internet GW Router will also be a central firewall for both routers.

Now any clients connected to Router 2 can access the Internet.

The Question You Probably Meant to Ask:

You appear to not care about configuring routers, but rather the most efficient way of splitting an expensive FTTP Fibre connection so (2) different apartments can share it.

If so, you could just connect a Wireless Access Point with an Ethernet cable to the Internet GW Router for Apartment 2. Indeed, a Wireless AP is really itself just a router. Adding Wireless AP's is more scalable and easier to maintain/troubleshoot than configuring multiple all-singing-and-dancing routers.

Although configuring a Wireless AP sounds complicated, I've largely automated the config of an inexpensive Raspberry Pi as a Wireless AP HERE