E-Lab 2.1.5 - Operation of the Cisco IOS
This lab demostrates how to upgrade the Cisco IOS image on the router. In order for this method of router upgrade to work, the router must be avle to access a TFTP server.
This lab will assume that the router has access to such a server. 
There are other advanced ways to upgrade or restore a router image, but this is the most common method used in normal situations.
Step 1
Enter into privileged EXEC mode.
No changes to the router can be performed in user EXEC mode.
Step 2
View the current Cisco IOS version.
Step 3
The current Cisco IOS image is version 11.2(1)T.
The next step loads the new image into the router.
Before loading the image, check the capacity of the router flash memory --
Does the router have enough room for the new image? (The new image is 4MB).
Use the correct show command to view the flash memory.
Step 4
Examine the output and notice the current IOS version. 
This router has been configured to access the TFTP server already.
When upgrading the IOS, the router will erase the old version and replace it with the new version.
Enter the command copy tftp flash to begin copying the new IOS from the server to the router.
Step 5
The remote TFTP server is located on IP address 172.16.9.11.
Step 6
The new Cisco IOS version to download from the TFTP server is 12.2(8)T and its filename is c1700-y-mz.122-8.T.bin.
Step 7
The next step requires the user to indicate the name of the image to use on the router. 
It is possible to enter a name different from the original name, however, that is not recommended.
If the Enter key is pressed the filename within the brackets will be used.
Step 8
Now check the image in flash memory again.
Notice the file has changed.
All that remains is for the router to be rebooted and the new image will be started.