|If you need help changing a subnet mask you're in way over your head and should hire a qualified consultant to help you.|
I will tell you this, you will have to change it on all dedicated network appliances (servers, printers, routers, etc) and on the DHCP server(s).
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.