How to find a connected router in the Network

[Derange]

Now to start i need to explain how i am usnig my network, i have several switches in different places because i am supplying internet to people around me and it is a very simple setup because i dont want to make it too big or complicated. Now the problem i have is that people are cheap and connectes their own Cable modems to make it wireless at their Place and that will give me an extra router in the system that is trying to be the main router. Problem with this is that half of the people connects to that one and the rest to the correct router. Of course i will get a lot of phone calls that net is not working so my question is how can i find out were the new router is? I have smart switches so i can turn off a port remotly but i need to know what port i should turn off.
The normal is that the new router ends up at the same ip as my router 192.168.0.1 but then i have this smart clients that i have configured the router for them but still they put the Wan Cable in the LAN port and then i get one router that has 192.168.8.1 with DHCP in that ip scoop.
So does anyone have a good idea how to solve this problem?

 

[jsmithepa]

Don't have an immediate answer.

Do you want to allow wireless AP or not? If yes, may as well tell them how to do it properly on a flyer, by your "normal," reserve a static range for their routers, then tell them don't use WAN port, disable DHCP.

May wanna add, "if you do this" no further support is provided.

 

[Derange]

They can connect whatever they want or rather they will do it anyway and i do tell them not to do that unless they have given me the router first but still i am in Kenya and lets say people dont really listen to me so i would like a way to find out who is messing the system up. Today i have to remove 1 Cable then check if it works then remove then next one and so on and i have 40 clients divided on to 5 switches placed i the area so it was a lot of running around. Now with my smart switches i can disable port port then check and so on but that takes too long to. Every Cable is marked so i know what Cable goes to what appartment so when i find the port from who is messing it up i can text them and tell them they have been disconnected but i would like to have some sort of program that can give me a MAC address then i can trace the port.

 

[Derange]

oh one thing i thought about when i bought my new switches D-Link DGS-1100 24 port was that if i set up different vlans on every port that this should remove the problem with people adding Cable modems or connecting a router badly. now is this something that could work? If so then i need to open a new thread and see if someone knows how to configure the switch, D-Link support are not helping me much there.