Comment by fuzzfactor

When I separated my scientific instruments from IT, I went to fixed IP and set each device to 192.A.B.x where x is different for each instrument or PC. And A & B are for my lab only, but definitely not the same as the "generic" address range IT is using.

One day somebody working days or nights "helpfully" plugged one of IT's loose office-machine-network cables into one of my little lab ethernet switches which had a vacant spot :\

With separate IP subnets it really kept the traffic from crossing, no damage was done, and nobody ever knew until a PC configured for DHCP was plugged into the lab network, and their router wanted to autoassign an IP address to it.