I need to find out why I have intermittent disconnection on my network whenever another device like the common home router is plugged on to the network. I have litle power to discourage this because I do work with Hotel/ Hospitality industry. What can I do to detect and block this devices when connected or make my network stable even when these devices are on the network?
Without more information such as the layout or a description of your network topology we can't really answer your question. I would suspect that you have a single broadcast domain, and therefore when I a rogue device that is running DHCP is plugged in that clients attach to it instead of your existing layer 3 design.
Have you enabled spanning tree protocol on your switches?