一、准备TFTP服务器

Router# ping tftp_address
...
!!!!!

确定TFTP服务器有足够的空间以及和设备的网络连通性。

二、备份IOS

R1#show flash: 
System flash directory:File  Length   Name/status3   33591768 c2900-universalk9-mz.SPA.151-4.M4.bin#注意这个文件名2   28282    sigdef-category.xml1   227537   sigdef-default.xml[33847587 bytes used, 221896413 available, 255744000 total]
249856K bytes of processor board System flash (Read/Write)R1# copy flash tftpSource filename []? c2900-universalk9-mz.SPA.151-4.M4.bin #文件名会在这里用到Address or name of remote host []? 10.1.1.100Destination filename [c2900-universalk9-mz.SPA.151-4.M4.bin]? Writing c2900-universalk9-mz.SPA.151-4.M4.bin....!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!![OK - 33591768 bytes]

三、从TFTP升级IOS

R1# copy tftp flashAddress or name of remote host []? 10.1.1.100
Source filename []? c2900-universalk9-mz.SPA.151-4.M4.binDestination filename [c2900-universalk9-mz.SPA.151-4.M4.bin]? 
%Warning:There is a file already existing with this name
Do you want to over write? [confirm]Accessing tftp://10.1.1.100/c2900-universalk9-mz.SPA.151-4.M4.bin...Loading c2900-universalk9-mz.SPA.151-4.M4.bin from 10.1.1.100: !!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
33591768 bytes copied in 0.419 secs (8417653 bytes/sec)R1#reload

四、备份配置文件到TFTP服务器

R1#copy running-config tftpAddress or name of remote host []? 10.1.1.100Destination filename [R1-confg]? Writing running-config...!!
[OK - 751 bytes]751 bytes copied in 0 secs

五、从TFTP下载配置文件

R1#copy tftp running-configAddress or name of remote host []? 10.1.1.100
Destination filename [R1-confg]? Writing startup-config...!![OK - 751 bytes]751 bytes copied in 0 secs