The command "no boot network" will prevent the device from attempting to locate a startup-config on the network (usually a TFTP Server). This command set (boot network, and no boot network) does not appear in the startup or running configs. If your device attempts to search for a config on the network when booting, issuing the no boot network command while in global config will stop this from occurring. (Again, the only way you know it is set is how it acts on boot)
Setting it up: boot network tftp myrouter.confg 10.0.0.1
Tearing it down: no boot network
Similar to this command is the "boot system" command set which will accomplish the same thing, but for an IOS image instead of a config.
Setting it up: boot system tftp c2800-k9-mz-123-12.bin 10.0.0.1
Tearing it down: no boot system
The "config-register" command sets the hex value for the boot sequence of the router. 0x2102 is the default setting which instructs the router to boot the startup-config on the router. 0x2142 instructs the router to bypass the startup-config on boot (necessary for password recovery). There are many other variances to the config-register commands. I would suggest doing a search for the specific setting you are looking for: i.e. console line speed, boot field, diagnostics, and many many more...
