如果你不小心使用了命令erase flash 那么发生什么就可想而知了。因此，建议在你拿到路由器等网络设备时 最好先将它的IOS等操作系统备份出来，以备万一！
本篇主要介绍通过Xmodem上传IOS的过程（以2610为例，不过这个方法用在其他设备上没什么太大区别）
准备工作，只要有Cisco原配的线缆就可以（注：Xmodem与实际的modem没有任何联系 只是一个传输协议 数据是通过终端的串口和路由器的Console口灌进去的）
在没有IOS的情况下 系统只能进入Rommon状态，在这个状态下只能见到如下命令：
rommon 8 ?
alias set and display aliases command
boot boot up an external process
break set/show/clear the breakpoint
confreg configuration register utility
cont continue executing a downloaded image
context display the context of a loaded image
cookie display contents of cookie PROM in hex
dev list the device table
dir list files in file system
dis display instruction stream
dnld serial download a program module
frame print out a selected stack frame
help monitor builtin command help
history monitor command history
meminfo main memory information
repeat repeat a monitor command
reset system reset
set display the monitor variables
stack produce a stack trace
sync write monitor environment to NVRAM
sysret print out info from last system return
tftpdnld tftp image download
unalias unset an alias
unset unset a monitor variable
xmodem x/ymodem image download
在这个模式下，输入Xmodem
rommon 9 xmodem
会提示如下警告：
WARNING: All existing data in bootflash will be lost!
Invoke this application only for disaster recovery.
Do you wish to continue? y/n [n]: y
Ready to receive file ? ...
然后在超级终端的传送栏目= 选择发送选项 = 再选择Xmodem 并指明IOS所在的路径即开始上传IOS,等待时间很长，视IOS的大小和传输速度。对于初次做IOS上传，建议不要去修改什么传输速率。传完以后 对整个系统初始化 界面如下：
Erasing flash at 0x603c0000
program flash location 0x602f0000
Download Complete!
program load complete, entry point: 0x80008000, size: 0x2f0074
Self decompressing the image : #################################################
################################################################################
################################################################################
################################################################# [OK]
Restricted Rights Legend
Use, duplication, or disclosure by the Government is
subject to restrictions as set forth in subparagraph
(c) of the Commercial Computer Software - Restricted
Rights clause at FAR sec. 52.227-19 and subparagraph
(c) (1) (ii) of the Rights in Technical Data and Computer
Software clause at DFARS sec. 252.227-7013.
cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134-1706
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-I-M), Version 11.3(6)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1998 by cisco Systems, Inc.
Compiled Tue 06-Oct-98 18:42 by ccai
Image text-base: 0x80008084, data-base: 0x80554578
cisco 2610 (MPC860) processor (revision 0x202) with 12288K/4096K bytes of memory
.
Processor board ID JAB0233005Z (3677578902)
M860 processor: part number 0, mask 32
Bridging software.
X.25 software, Version 3.0.0.
1 Ethernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
32K bytes of non-volatile configuration memory.
4096K bytes of processor board System flash (Read/Write)
Press RETURN to get started!
00:00:06: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up
00:00:06: %LINK-3-UPDOWN: Interface Serial0/0, changed state to up
00:00:06: %SYS-5-CONFIG_I: Configured from memory by console
00:00:06: %SYS-5-RESTART: System restarted --
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-I-M), Version 11.3(6)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1998 by cisco Systems, Inc.
Compiled Tue 06-Oct-98 18:42 by ccai
00:00:07: %LINEPROTO-5-UPDOWN: Line protocol on
WL_bank_2610_2Interface Ethernet0/0, changed state to up
00:00:07: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed sta
te to up
00:00:07: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed sta
te to up
2610_2
