How to make three routers see each each devices connected across them?

Question

I have 3 routers. 1 of which is from my ISP and the other 2 I use to extend my wifi connection on ground floor and second floor of our house. See setup in image below.

I was following this tutorial. But it seems that for my use case that two routers are connected to one modem, It doesn't seem to apply.

My Problem is that Router 2 and 3 cannot see devices connected to either one of them. Hence, if my NAS is configured on router 2, only devices connected to Router 2 could see it and not those on router 3 which would make it impossible for me to configure my IP Cameras connected on router 3 to record on the NAS.

To make matters worst for me, I can't make Router 2 work in AP mode since alot of its features are disabled like traffic analysis etc hence I had it work in router mode unlike Router 3. See differences in features below.

Router 2 in AP Mode.

Router 2 in Router Mode.

I tried changing the LAN IP address of my router 2 to the same octet used by my router 1 and 3, but to no avail, internet and lan is not working at all. Internet would only work if I changed the WAN IP address to the same octet of the router 1, but if I had it that way, the router wont allow me to change the LAN IP address to the same 3rd octet as it says LAN and WAN Ips should be different.

Other notes:

• DHCP is enabled on Router 2 and 1
• DHCP is disabled on Router 3
• I cannot disabled DHCP on Router 1 along with manually assigning IP
• address to certain macs, as this is an ISP modem and I have no admin access.

How can I configure this network to make router 2 and router 3 see devices connected on each other so that they can share NAS as well as be able to configure the routers 3 gateways no matter where I connect to?.

BTW, my Aim is:

• I am trying to save around 10-15 bucks and wiring mess by not buying another 20 meter CAT6 ethernet cable and making Router 2 the main router and connecting my Router 3 to router 2 instead of router 1. I am also trying to make router 1 still useful and accessible to the network since router 1 has free 3x gigabit ports that my router 3 wifi repeater doesnt have. Hence if I connect our smart tv and another old IP Camera via LAN, other devices should still be able to see it in the network to be able to take advantage of being able to configure the gateways of routers etc.

I just happen to read somewhere too, that apparently, the setup that I have atm where my router 2 cant see the other devices on router 3 is what is called a Cascaded network as seen in this blog.

Answer 1

I tried changing the LAN IP address of my router 2 to the same octet used by my router 1 and 3, but to no avail, internet and lan is not working at all. Internet would only work if I changed the WAN IP address to the same octet of the router 1, but if I had it that way, the router wont allow me to change the LAN IP address to the same 3rd octet as it says LAN and WAN Ips should be different.

The message is correct – they are physically two separate networks (precisely because you have a router in between!), so their IP network numbers must be different. Changing the network numbers to be identical will not help you here – (if a city has two streets that happen to be identically named, they're still two separate streets).

I can't make Router 2 work in AP mode since alot of its features are disabled like traffic analysis etc hence I had it work in router mode

If you want to merge both sides into a single flat network, Router#2 must not be acting as a router. If Router#2 acts as a router, you will have two subnets on both sides. You can't really have it both ways at the same time.

So if you want "traffic analysis" &c. then you will need to keep two separate subnets and route traffic between them. That's a normal thing to do (plenty of large networks consist of many subnets), and will easily allow you to reach devices across networks by their exact IP address, but you won't be able to use 'device discovery' features that some of your camera tools might have.

But at least in my (short) experience with IP cameras, only the initial configuration needs to be done with such tools – so you'll have to connect to the same subnet at first, but once you've assigned them an IP address once, you'll be able to reach them across routers just fine.

To make this work, add a static route on Router#1 pointing it towards Router#2's subnet:

Destination network:  192.168.2.0 / 24
Netmask:              255.255.255.0
Gateway:              192.168.1.??? (Router#2's "WAN" IP address)

Afterwards, make sure the firewall rules on Router#2 allow packets from the "WAN" side. (It's not really the "WAN" in your situation.)