Subnetting and node isolation

Question

I'd just like to ask about networking... I'm a total novice to networking so I'm sorry if this isn't possible but I think it is.

I have 2 Sky SR101 routers. One is connected to the modem and currently hosts all the devices in the house (54 total). I live with my dad and grandparents, who own most of the devices. I only own 4 of them (not including the second router).

The main router has the IP address 192.168.0.1, and subnet mask 255.255.255.0 by default.

If it's possible, I'd like to make a subnet, where most of the devices still reside on one subnet (eg, 192.168.0.x) and my four devices reside on another subnet (eg 192.168.1.x) using the spare second router. I've looked for tutorials on the Internet about how to do this but they really overcomplicate it and don't even tell you how to configure the router with the numbers you come out with.

Again, if possible, these subnets should be able to communicate individually with the Internet but not with each other, as the whole reason for this idea is my dad constantly messing with my PC and chromecast.

I've done some research and I understand that I need to use the subnet mask 255.255.255.192 to allow 4 subnets, as 255.255.255.128 seems to be flaky as many people say it doesn't work but many say it does.

I can get the two routers working if I have one network use addresses 192.168.0.1 - 62, and another using 192.168.0.63 - 128, but when I do this the devices completely bypass the second router, essentially just using it as a switch, and use the DHCP server from the main router which just means it's still accessible by my dad's annoying tricks. If I set the secondary network to use 192.168.1.x then there's no Internet access, and the devices still sometimes use the DHCP server from the main router, giving them a 192.168.0.x address.

Any help is much appreciated as I'm still just a noob. Many thanks!

Answer 1

Put your 2nd router as a normal device under the 1st Router. Your 2nd router will have the "WAN" IP of 192.168.0.x, but you can set up your own "internal" IP of 192.168.1.x/255.255.255.0.

This means all devices connected to your 2nd router will have IP of 192.168.1.x, and will have internet connectivity, but anything on the "WAN" side (general internet, and devices on the 1st router with IP of 192.168.0.x) will not be able to see inside into the 192.168.1.x range.

              +-----------+
              |  Internet |
              |           |
              +-----------+
                    |
                    |
                    |
             +------------+
             | SR101      | 192.168.0.x
             | 1st Router | DHCP
             +------------+
                    |
                    |
                    | 192.168.0.y (uplink/WAN)
+------------+------------+-------------------+
             | SR101      |
             | 2nd Router |
             +------------+
               |      |     192.168.1.x
        +--------+    |     DHCP
        | Device1|    |
        +--------+    |
               +-------+
               |Device2|
               +-------+

I hope this make sense.