I ask very basic qus. I dont know how to upgrade the IOS? If my remote location already installed the ROuter with very big config. I dont wont the lost the data and IOS want to be upgrade.? (and I am Remote location location I want upgrade to remote location)
What are the steps please help me.
the configuration file is saved in NVRAM ( non volatile RAM), the IOS image is saved in an internal flash filesystem.
the biggest risk is that if the new IOS image is not loaded successfully the device may stuck in rommonitor and can become unreachable.
you can upload with TFTP the configuration file using
copy startup-confi tftp
Basically for IOS images lower then 33 MB you can use TFTP protocol to tranfer the image file into router's flash file system
current IOS image is listed in show ver
you need to check if there is enough space to store the new file
you can use
to see all filesystems that are present
if the flash has enough space you need to copy the image file into the flash using
copy tftp flash:
at the end of the transfer you need to verify the size of the file and depending in file system version you can use verify command to check checksum of the file in flash.
IF everything is fine you can modify the router configuration in order to tell the router to attempt to boot using the new image file
you need a line like
boot system flash:filename
again the exact name of the "drive" flash: or other depends from platform the name can be disk0: or other do no place any space between "drive" and filename.
you can put a line pointing to current image
you need to save the configuration and to verify with
show conf | inc boot system
that the first line that appears is boot system flash:newfilename if not you need to remove the line(s) before using
no boot system flash:oldname
if necessary save again
at this point you can attempt to reload the router
if in the flash there is not enough space to store both the current image and the new one the things are more difficult.
you will need to delete the IOS image that is in use (before upload it using copy flash tftp in order to keep a copy), to squeeze the flash to free space (this depends from filesystem type it may be needed or not)
then you can copy down the new IOS image
However, if the router is powered off after deletion of the current IOS image it will be stucked in rom mon and you will not be able to reach it from remote
Hope to help