@TP-Link 

I have a rather large home network with 2 Deco X90s with their own subnets pointing to my main router which is connected to a cable modem with its own subnet. The main router has a firewall so everything downstream from that is protected. The firewall on the X90s serves no purpose and it makes it impossible for me to communicate with devices on either Deco subnet from my main subnet.

@TP-Link 

That won't work as I need the separate subnets as I have lots of devices which need IP addresses.

@TP-Link 

So is there a way to disable the firewall? Even if it's a debug or hidden mode that's fine. 

If not is there some other solution so I can route between my main router and devices on the Deco subnets?

@wayne5w 

Can you share more information about your home network? That would help to figure if you could achieve what you want with Deco X90, or you selected wrong networking gear for your home network.

You said you run two X90 with their own subnets. Does it mean you run each X90 as its own standalone router, which means each of them is Main Deco on its own network? If not, do you run both X90s in a single Deco mesh, with Main Deco X90 and Satellite Deco X90?

You said you have "lots of devices." Can you be more specific: is total number under 200, is it over 300 but less than 1,000? More than 1,000, perhaps?

What is your main router name (brand) and model number?

What did you have to provide all these devices with WiFi before you bought Deco, and why did you decide to buy Deco?

@Alexandre. 

>>Does it mean you run each X90 as its own standalone router, which means each of them is Main Deco on its own network

That's correct. Each deco is a standalone router and both point to the main router.

>>You said you have "lots of devices." Can you be more specific: is total number under 200, is it over 300 but less than 1,000? More than 1,000, perhaps?

Haven't counted them all but over 500.

>>What is your main router name (brand) and model number?

Netgear Nighthawk RAX200 which is a beast of a router.

>>What did you have to provide all these devices with WiFi before you bought Deco, and why did you decide to buy Deco?

Didn't have this issue before. Recently added a large addition to the house.

>>that would help to figure if you could achieve what you want with Deco X90, or you selected wrong networking gear for your home network.

If I can turn the firewall in the Deco's off then I selected the right gear, if not I selcted the wrong gear.

@wayne5w 

>If I can turn the firewall in the Deco's off then I selected the right gear, if not I selected the wrong gear.

Short answer: you can't turn off firewall on a router. 

Longer answer: the correct configuration for your home network with hardware you have would be to let Netgear Nighthawk RAX200 manage your home network (IP addresses allocations, DHCP lease and such), preferably with its WiFi turned off, while letting X90s provide WiFi coverage only with both running as a single Deco mesh in Access Point mode.

In that configuration you won't be having issues with devices communicating with each other.

I checked user manual for Netgear Nighthawk RAX200, it is indeed quite powerful and flexible router. With proper netmask and IP range configured it should be able to manage 500+ devices, or at least I haven't found anywhere that it can't.

If this configuration is not what you want to consider, you should look for a different networking equipment instead of Deco mesh. 

@Alexandre. 
 

The nighthawk is limited to one subnet, 255 IPs is not enough.

I like the Deco but the lack of settings and features is a real dea killer.

@wayne5w 

By default, Netgear Nighthawk RAX200 is set to support 255 clients. 

Try the following netmask and DHCP range in Netgear Nighthawk RAX200, this should work for 2000 clients:

Subnet ID 172.16.0.0/21
Mask  255.255.248.0
Range 172.16.0.1 - 172.16.7.254
Broadcast 172.16.7.255