Router Overview - Using TFTP for IOS Backups and Updates

In the event of a network catastrophe, it is possible for a router’s IOS system image to be corrupted or erased from flash memory altogether. Standard procedure is to maintain a backup image of every IOS version in use in the network being managed. These backup IOS images are maintained on TFTP servers or within network management applications such as CiscoWorks (covered in Chapter 15).

TFTP stands for Trivial File Transfer Protocol. TFTP is a TCP/IP application derived from the early days of the UNIX operating system. As you may have guessed, TFTP is a stripped-down version of FTP, the command many of you have used to download files over the Internet. IOS uses TFTP instead of FTP because it’s speedier and uses fewer system resources.

So-called TFTP servers are computer platforms on an internetwork that store and download IOS system images and configuration files. It is recommended that more than one TFTP server be used to back up a network. This is in case the TFTP server itself goes down or the network segment connecting it to the devices it backs up becomes unavailable.

To load a new IOS image to a router’s flash memory, use the copy tftp flash command following the procedure, shown here:

Router#copy tftp flash

System flash directory:
File    Length     Name/status
  1     4171336    c4500-j-mz_112-15a.bin
[4171400 bytes used, 22904 available, 4194304 total]
Address or name of remote host [10.1.10.40]? 10.1.10.40
Source file name? c4500-j-mz_112-15a.bin
Destination file name [c4500-j-mz_112-15a.bin]? <cr>
Accessing file 'c4500-j-mz_112-15a.bin' on 10.1.10.40...
Loading c4500-j-mz_112-15a.bin from 10.1.1.12 (via TokenRing1): [OK]

Erase flash device before writing? [confirm]yes
Flash contains files. Are you sure you want to erase? [confirm]yes

Copy 'c4500-j-mz_112-15a.bin' from server
as 'c4500-j-mz_112-15a.bin' into Flash WITH erase? [yes/no]yes
Erasing device... eeeeeeeeeeeeeeee ...erased
Loading c4500-j-mz_112-15a.bin from 10.1.1.12 (via TokenRing1): !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
[OK - 4171336/4194304 bytes]

Verifying checksum... OK (0x29D5)
Flash copy took 00:00:30 [hh:mm:ss]
Router#

You can see that the TFTP server confirmed that it had the IOS system image before overwriting the one in the router’s flash memory. Each exclamation point in the display indicates that a block of the file was successfully copied over the network from the server to the router.

NOTE: If you are copying a file to a TFTP server, be sure the name of the file that you are attempting to transfer already exists in the TFTP directory. Create the file on UNIX systems using the touch command. On Microsoft platforms, open Notepad to create the file and save it under the filename.

This chapter is from Cisco: A Beginner's Guide, by Velte and Velte (McGraw-Hill/Osborne, 2004, ISBN: 0072256354). Check it out at your favorite bookstore today.  Buy this book now.

Next: The Configuration File >>
 

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