Depends what you mean override. The PC will always use what you have set no matter what the router says. This does not mean the PC can control the router by doing this. The router will continue to give out IP addresses if it is requested. If it is smart it will ping the address before giving it out to another machine. You machine should respond to the ping and it should prevent the ip from being given to another device. You can sometimes end up with duplicate addresses this way. Now if you set your ip or subnet to something completely different than the router is using then it just won't work because the router is in control of the gateway so the ip and subnet must match the range defined by the router.