A router that can keep its system image in local non-volatile storage MAY be configurable to boot its system image over the network. A router that offers this option SHOULD be configurable to boot the system image in its non-volatile local storage if it is unable to boot its system image over the network.
It is important that the router be able to come up and run on its own. NVRAM may be a particular solution for routers used in large networks, since changing PROMs can be quite time consuming for a network manager responsible for numerous or geographically dispersed routers. It is important to be able to netboot the system image because there should be an easy way for a router to get a bug fix or new feature more quickly than getting PROMs installed. Also if the router has NVRAM instead of PROMs, it will netboot the image and then put it in NVRAM.
Routers SHOULD perform some basic consistency check on any image loaded, to detect and perhaps prevent incorrect images.
A router MAY also be able to distinguish between different configurations based on which software it is running. If configuration commands change from one software version to another, it would be helpful if the router could use the configuration that was compatible with the software.