Refer to the exhibit.
For what two reasons has the router loaded its IOS image from the location that is shown?
(Choose two.)
A.
Router1 has specific boot system commands that instruct it to load IOS from a TFTP server.
B.
Router1 is acting as a TFTP server for other routers.
C.
Router1 cannot locate a valid IOS image in flash memory.
D.
Router1 defaulted to ROMMON mode and loaded the IOS image from a TFTP server.
E.
Cisco routers will first attempt to load an image from TFTP for management purposes.
Explanation:
The loading sequence of CISCO IOS is as follows:
Booting up the router and locating the Cisco IOS
1. POST (power on self test)
2. Bootstrap code executed
3. Check Configuration Register value (NVRAM) which can be modified using the config-register command
0 = ROM Monitor mode
1 = ROM IOS
2 – 15 = startup-config in NVRAM
4. Startup-config filE. Check for boot system commands (NVRAM)
If boot system commands in startup-config
a) Run boot system commands in order they appear in startup-config to locate the IOS
b) [If boot system commands fail, use default fallback sequence to locate the IOS (Flash, TFTP, ROM)?]
If no boot system commands in startup-config use the default fallback sequence in locating the IOS:
a) Flash (sequential)
b) TFTP server (netboot)
c) ROM (partial IOS) or keep retrying TFTP depending upon router model
5. If IOS is loaded, but there is no startup-config file, the router will use the default fallback
sequence for locating the IOS and then it will enter setup mode or the setup dialogue.
When powered on, the router first checks its hardware via Power-On Self Test (POST). Then it checks the configuration register to identify where to load the IOS image from. In the output above we learn that the Configuration register value is 0×2102 so the router will try to boot the system image from Flash memory first.
But we also see a line “System image file is “tftp://112.16.1.129/hampton/nitro/c7200-j-mz”. Please notice that this line tells us the image file that the device last started. In this case it is from a TFTP server. Therefore we can deduce that the router could not load the IOS image from the flash and the IOS image has been loaded from TFTP server.
Note:
If the startup-config file is missing or does not specify a location, it will check the following locations for the IOS image:
+ Flash (the default location)
+ TFTP server
+ ROM (used if no other source is found)
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