Allow two different subnets to communicate - Deco M9 Plus
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Hello,
I currently have both my ISP provided modem/router and the Deco M9 Plus in Router Mode. The thing is that they're on different subnets and can't find each other at all. For example, the subnets are:
- ISP Modem/Router: 192.168.0.0/24, gateway 192.168.0.1
- Deco M9 Plus: 192.168.2.0/24, gateway 192.168.2.1
I cannot ping any device between subnets, other than the gateways (i.e., if I ping 192.168.0.1 from the Deco subnet, it works, but not my Raspberry Pi at 192.168.0.30). I searched the internet for a solution and I do not want to use AP mode. I want it on Router Mode for the benefits. I also found something about NATs and disabling the NAT in the second router (i.e. the Deco's) so that only the main router (i.e. the ISP router) is using NAT (something called double natting or whatever) but I can't seem to find how to disable NAT in the Deco's.
So far I seem to have it working one way (one subnet to the other, but not the other way around), where if I put the ISP routers gateway (192.168.0.1) as a Primary DNS on the Deco's DHCP server settings, I can communicate with devices on the ISP's router subnet from the Deco's. I tried doing the same but with the Deco's gateway on the ISP router but it didn't work.
I currently have my network setup as below:
ISP Modem/Router ---> Main Deco ---> Switch ---> Slave Decos
This enables the ethernet backhaul feature.
Before having the Deco's, I had a very cheap Nexxt router connected to the ISP Router in a similar setup and it allowed communication between both subnets without any prior configuration, so I'm honestly lost.
Your setup worked with Nexxt router, because you must have configured it as Wireless Repeater for your ISP Router. You can't do that with Deco mesh.
What you have now is two independent routers, ISP Router and Main Deco, connected to each other. What you see as a result, is by design. Main Deco considers everything connected to it your home network, treats everything outside of your home network as Internet, and that includes devices connected to ISP router. It would be bad if anyone from the Internet is able to connect to your home network devices, would not it? Main Deco behaving as a router prevents that from happening.
The easiest solution to your issues, and one which won't give you headaches in the future, would be to connect every wired device and every wireless device on your home network to Main Deco.
Turn off WiFi on ISP router, and have your network set up as following:
You may also consider configuring ISP Router as a modem only. That is not necessary if your apps and devices connected to Deco mesh don't complain about double NAT and connect to the Internet without issues.