For example, there's 4400 series router may have modules installed, such as in this bottom example or
may not have modules installed.
So when the router boots up, it's got to determine what interfaces it has inserted, what modules are
available, how much RAM is available, and various other components.
You could even install a UCS server into a router today.
So when the rubber boots up, it needs to determine what's physically installed and available on the
router.
So the power on self-test will test the basic functionality of the router hardware to determine whether
it's working, determine whether it's supported, and determine which components are present.
As an example, you may have mistakenly inserted a voice interface card into a WAN interface card slot.
Voice interface cards or
VICs may need to be inserted into specific modules and you may have inserted the wrong card into the
wrong module on a router.
So it needs to do this power and self-test to determine what's installed and whether things are installed
correctly and working correctly.
ROM Monitor includes a low-level operating system that is used for troubleshooting, password recovery and
testing.
This is different to the standard operating system and doesn't support routing.
You could use ROM Monitor as an example to download a router operating system if there's none available
on the router
or you could use ROM Monitor to do a password recovery, which I'll demonstrate in this course.