I have a network with 500+ computers, at my area there is lots of cooperation companies that sometimes bring their own routers. If they do it in sneaky way and do not turn off DHCP service on the device many devices get wrong addresses and it takes long time to find it. Is there any solution?
I thought of isolating department or building with VLANs with separate subnets. I thought also of using static arp on main switches and put entry with 192.168.0.1 and 192.168.1.1 to my DHCP. Does it make sense, will it secure address changes in any way?