本人长期从事计算机网络管理工作，在对CISCO路由器的长期日常维护和管理实践中积累了一定的经验。现总结归纳出CISCO路由器IOS映像升级的几种方法，供广大网络爱好者或同仁参考。在介绍CISCO路由器IOS升级方法前，有必要对Cisco路由器的存储器的相关知识作以简单介绍。路由器与计算机相似，它也有内存和操作系统。在Cisco路
由器中，其操作系统叫做互连网操作系统(Internetwork Operating System)，常简称为IOS。路由器的存储器主要有：
ROM:只读存储器包含路由器正在使用的IOS的一份副本；
RAM:IOS将随机访问存储器分成共享和主存。主要用来存储运行中的路由器配置和与路由协议有关的IOS数据结构；
FLASH (闪存)：用来存储IOS软件映像文件，闪存是可以擦除内存，它能够用IOS的新版本覆写，IOS升级主要是闪存中的IOS映像文件进行更换。
NVRAM：非易失性随机访问存储器，用来存储系统的配置文件。
IOS升级方法一
在对能够正常启动的CISCO路由器的IOS进行升级时，比较简单。具体步骤如下：
1、寻找一种TFTP服务器软件（有CISCO公司的TFTPServer或3COM公司的3Cserver等，在升级较大IOS映象文件时，建议用3Cserver），安装在一台计算机上，将要升级的IOS映象文件拷贝到相关的目录中（例：D:\），并运行TFTP服务器软件，通过菜单设置Root目录为拷贝IOS映象文件所在目录（如D:\）。假设该计算机的IP地址为10.32.10.1；
2、连接路由器的console口与PC机的COM1，使用PC的超级终端软件访问路由器，将路由器的地址设为10.32.10.32（与计算机的IP地址同网段即可）。建议在进行IOS升级前将原有IOS文件备份下来，防止待升级的IOS文件存在问题不可用；
QUOTE:
Router# dir flash: (查看目前IOS映象文件名，也可用Router#Show version)
Directory of flash:/
1 -rw- 5998292 C2600-I-MZ.122-11.BIN
8388608 bytes total (2390252 bytes free)
Router#copy flash tftp （备份IOS文件）
Source filename []?c2600-i-mz.122-11.bin
Address or name of remote host []? 10.32.10.1 (TFTP服务器地址)
Destination filename [c2600-i-mz.122-11.bin]?
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
…
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
5998292 bytes copied in 324.071 secs (18509 bytes/sec)
Router#
3、对路由器进行IOS升级；
QUOTE:
Router#copy tftp flash
Address or name of remote host []? 10.32.10.1 (TFTP服务器地址)
Source filename []? c2600-i-mz.122-11.bin （需升级的新IOS映象文件名）
Destination filename [c2600-i-mz.122-11.bin]?
Do you want to over write? [confirm]
Accessing tftp://10.32.10.1/c2600-i-mz.122-11.bin...
Erase flash: before copying? [confirm]
Erasing the flash filesystem will remove all files! Continue? [confirm]
Erasing device... eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ...erasedee
Erase of flash: complete
Loading c2600-i-mz.122-11.bin from 10.32.10.1 (via Ethernet0/0): !!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
…
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
[OK - 5998292 bytes]
Verifying checksum... OK (0xA0C0)
5998292 bytes copied in 318.282 secs (18846 bytes/sec)
Router#
IOS升级方法二
由于升级失败后或者路由器的config-register寄存器值为0x2101时，开启路由器时、或者在开启（某些型号）Cisco路由器的电源开关后30秒内按下Ctrl+break键，中断路由器的正常启动，路由器都会进入rom监视模式,即Router(boot)>，在这种情形下，对路由器的IOS进行升级，也比较简单。首先进入特权模式下，即
QUOTE:
Router(boot)>en
Router(boot)#
其他升级步骤同方法一，即：执行copy tftp flash命令，对IOS进行升级。升级完成后，不要忘了修改config-register寄存器值为0x2102（恢复正常值）。
QUOTE:
Router(boot)# t
Router(boot)( config)# config-register 0x2102
Router(boot)( config)#exit
Router(boot)#wr
Router(boot)#reload
重启即可。IOS升级方法三
由于不小心使用了命令erase flash或升级失败后或在开启（某些型号）Cisco路由器的电源开关后30秒内按下Ctrl+break键，中断路由器的正常启动，路由器都会进入rom监视模式,即 rommon 1>，在这种情形下，对路由器的IOS进行升级，情况要稍微复杂一点。在rommon 1>状态下，可键?请求帮助。(1为命令行序号，每执行1条命令自动加1)
QUOTE:
rommon 1 > ?
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
rommon 2 >
在rommon 1>状态下有两种升级IOS方法。
（一）、通过Xmodem命令（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）升级IOS，具体步骤如下：
1、用Cisco原配的线缆连接路由器的console口与PC机的COM1，使用PC机的超级终端软件访问路由器，这时不需要对PC和路由器配置任何地址。
2、在这个模式下，输入Xmodem命令，即：
QUOTE:
rommon 2 > xmodem -c c2600-i-mz.122-11.bin
（-c是带校验，c2600-i-mz.122-11.bin为存放在PC机上的IOS映像文件）
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 c2600-i-mz.122-11.bin ... （此时在超级终端的传送栏目=> 选择发送文件选项 => 再选择Xmodem 并指明IOS映像文件所在的路径，按发送即开始上传IOS,等待时间很长，视IOS的大小和传输速度。）
QUOTE:
Erasing flash at 0x607c0000
program flash location 0x605b0000
Download Complete!
传完以后，对整个系统初始化 显示如下：
QUOTE:
program load complete, entry point: 0x80008000, size: 0x5b85e0
Self decompressing the image : #################################################
################################################# [OK]
Smart Init is disabled. IOMEM set to: 10
Using iomem percentage: 10
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 12.2(11)T9, RELEASE SOFTWARE (fc1)
TAC Support:
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Mon 23-Jun-03 15:42 by cmong
Image text-base: 0x8000809C, data-base: 0x80A68B48
cisco 2610 (MPC860) processor (revision 0x203) with 22528K/2048K bytes of memory
Processor board ID JAD03483395 (1128032249)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash (Read/Write)
Press RETURN to get started!
*Mar 1 00:00:05.652: %PA-2-UNDEFPA: Undefined Port Adaptor type 100 in bay 1
*Mar 1 00:00:07.996: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up
*Mar 1 00:00:07.996: %LINK-3-UPDOWN: Interface Serial0/0, changed state to down
*Mar 1 00:00:07.996: %LINK-3-UPDOWN: Interface Serial0/1, changed state to down
*Mar 1 00:00:09.142: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up
*Mar 1 00:00:09.142: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down
*Mar 1 00:00:09.142: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1, changed state to down
*Mar 1 00:00:09.458: %SYS-5-CONFIG_I: Configured from memory by console
*Mar 1 00:00:11.245: %LINK-5-CHANGED: Interface Serial0/1, changed state to administratively down
*Mar 1 00:00:12.275: %SYS-5-RESTART: System restarted --Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-I-M), Version 12.2(11)T9, RELEASE SOFTWARE (fc1)
TAC Support:
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Mon 23-Jun-03 15:42 by cmong
*Mar 1 00:00:12.279: %SNMP-5-COLDSTART: SNMP agent on host NE16 is undergoing a cold start
Router>
采用这种方法时，由于使用console口来传送，速率为9600bps，需要时间较长。因此可修改console口速率利用xmodem命令实现快速升级IOS。具体方法如下：
QUOTE:
rommon 1 > confreg 回车
Configuration Summary
enabled are:
load rom after netboot fails
console baud: 9600
boot: image specified by the boot system commands
or default to: cisco2-C2600
do you wish to change the configuration? y/n [n]: y (选择 yes)
enable "diagnostic mode"? y/n [n]: n (选择 no)
enable "use net in IP bcast address"? y/n [n]: n (选择 no)
disable "load rom after netboot fails"? y/n [n]: n (选择 no)
enable "use all zero broadcast"? y/n [n]: n (选择 no)
enable "break/abort has effect"? y/n [n]: n (选择 no)
enable "ignore system config info"? y/n [n]: n (选择 no)
change console baud rate? y/n [n]: y (选择 yes)
enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400
4 = 19200, 5 = 38400, 6 = 57600, 7 = 115200 [0]: 7 (选择 7,用最大的11520
速率的xmodem传输)
change the boot characteristics? y/n [n]: n (选择 no)
Configuration Summary
enabled are:
load rom after netboot fails
console baud: 115200
boot: image specified by the boot system commands
or default to: cisco2-C2600
do you wish to change the configuration? y/n [n]: n (选择 no)
You must reset or power cycle for new config to take effect
rommon 2 > reset 回车
注意：在按reset键前，需要修改串口速度（我的电脑---端口属性----串口速度调为115200），然后再修改超级终端里设置速率为115200，记住，一定要这么做，否则会出现乱码！ 然后关闭这个超级终端，重新建立一个超级终端连接，重新启动系统后，出现
QUOTE:
rommon 1> 提示符
然后,输入
QUOTE:
rommon 1> xmodem -r
Do not start the sending program yet...
Invoke this application only for disaster recovery.
Do you wish to continue? y/n [n]: y (选择 yes)
Ready to receive file ...
此时，在超级终端的菜单上的“传送”---“发送文件”----选择IOS映像文件所在地以及选择使用“xmodem”协议，点击“发送”即可。等待10-20分钟左右就可升级完3-6M的IOS文件！待升级完成后，请记住修改回计算机串口与超级终端、路由器confreg下的xmodem等传输速率为9600bps。
方法如下：
QUOTE:
Router>en 进入新IOS的特权模式
Router#reload 重启系统
Proceed with reload? [confirm] 回车
00:01:04: %SYS-5-RELOAD: Reload requested
System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)
Copyright (c) 1999 by cisco Systems, Inc.
TAC:Home:SW:IOS:Specials for info
PC = 0xfff0a530, Vector = 0x500, SP = 0x680127b0
C2600 platform with 24576 Kbytes of main memory
PC = 0xfff0a530, Vector = 0x500, SP = 0x80004684
monitor: command "boot" aborted due to user interrupt
30秒内按ctrl+break键
rommon 1 > confreg （ 输入“confreg”命令）
Configuration Summary
enabled are:
load rom after netboot fails
console baud: 115200
boot: image specified by the boot system commands
or default to: cisco2-C2600
do you wish to change the configuration? y/n [n]: y (选择 yes)
enable "diagnostic mode"? y/n [n]: n (选择 no)
enable "use nn IP bcast address"? y/n [n]: n (选择 no)
disable "load rom after netboot fails"? y/n [n]: n (选择 no)
enable "use all zero broadcast"? y/n [n]: n (选择 no)
enable "break/abort has effect"? y/n [n]: n (选择 no)
enable "ignore system config info"? y/n [n]: n (选择 no)
change console baud rate? y/n [n]: y (选择 yes)
enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400
4 = 19200, 5 = 38400, 6 = 57600, 7 = 115200 [7]: 0 (选择 0,改回用标准速率速率9600的xmodem传输)
change the boot characteristics? y/n [n]: n (选择 no)
Configuration Summary
enabled are:
load rom after netboot fails
console baud: 9600
boot: image specified by the boot system commands
or default to: cisco2-C2600
do you wish to change the configuration? y/n [n]: n You must reset or power cycle for new config to take effect
rommon 2 >
此时手工改回计算机串口与超级终端2者传输速率为9600
然后敲入
QUOTE:
rommon 2 >reset
最好关掉电源后，重新启动。利用xmodem命令实现路由器IOS升级速度较慢，往往等上很长时间，为了快速升级，可以采用下列方法。