An instance that loads Cisco router IOS in TFTP and ROM

The question about Cisco router IOS is described in the following aspects: how to load in flash, TFTP, or ROM? The following example shows how to use a set of boot system commands to specify the location where the cisco IOS software is loaded.

1. Load from Flash:

In the configuration process, flash is usually configured as the first location to load the Cisco router IOS image. Loading from flash will not be affected by network problems, even if the network is faulty, unable to connect to the TFTP server normally, the router can also load IOS images normally.
It168 # configure terminal
It168 (config) # boot system flash my-router [ctrl-z]
It168 # copy running-config startup-config

When using the boot system command, we need to enter the boot system command in global configuration mode and locate the location of the Cisco router IOS and the image file name.

2. load from the TFTP Server

After loading IOS images from the TFTP server is defined in boot system, when loading IOS images from flash fails, you can load IOS images from the TFTP server.
It168 # configure terminal
It168 (config) # boot system tftp IOS-BAK 129.0.0.2 [ctrl-z]
It168 # copy running-config startup-config

3. Load from ROM

If both flash and TFTP fail and the Cisco router IOS image cannot be properly loaded, we can only load the image from the ROM, the IOS image loaded from the ROM can only execute some IOS commands and functions.
It168 # configure terminal
It168 (config) # boot system rom [ctrl-z]
It168 # copy running-config startup-config

Tip: when using the boot system command, pay attention to the order in which the command is entered. Generally, the command is loaded in the order of flash, TFTP, and ROM, in addition, after changing all configurations, copy the configurations to NVRAM. Otherwise, when you restart the vro, the configurations of Cisco router IOS will not take effect.