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；
2、连接路由器的console口和PC机的COM1，使用PC的终极终端软件访问路由器，将路由器的地址设为（和计算机的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
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
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]
? ???Erase flash: before copying? [confirm]
? ???Erasing the flash filesystem will remove all files! Continue? [confirm]
? ???Erasing device... eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ...erasedee
? ???Erase of flash: complete
: !!!!!!!!!!!!!!
? ???!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
? ???…
? ???!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
? ???[OK - 5998292 bytes]
? ???Verifying checksum...??OK (0xA0C0)
? ???5998292 bytes copied in 318.282 secs (18846 bytes/sec)
? ???Router#
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
IOS升级方法二
由于升级失败后或路由器的config-register寄存器值为0x2101时，开启路由器时、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和实际的modem没有所有联系 只是个传输协议 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口和PC机的COM1，使用PC机的终极终端软件访问路由器，这时不必对PC和路由器设置所有地址。
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 ...? ?? ?（此时在终极终端的传送栏目=> 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,等待时间非常长，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:
? ???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)
? ???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
? ???M860 processor: part number 0, mask 49
? ???Bridging software.
? ???
? ???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（我的计算机---端口属性----串口速度调为115200），然后再修改终极终端里设置速率为115200，记住，一定要这么做，否则会出现乱码！ 然后关闭这个终极终端，重新建立一个终极终端连接，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，在终极终端的菜单上的“传送”---“发送文件”----选择IOS映像文件所在地及选择使用“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和终极终端、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
? ???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和终极终端2者传输速率为9600
然后敲入
QUOTE:
? ???rommon 2 >reset
最佳关掉电源后，重新启动。利用xmodem命令实现路由器IOS升级速度较慢，往往等上非常长时间，为了快速升级，能采用下列方法。
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++=
（二）通过tftpdnld命令升级IOS，具体步骤如下：
1、用Cisco原配的线缆连接路由器的console口和PC机的COM1，使用PC机的终极终端软件访问路由器；用
一根双绞线连接路由器的eth0/0口和PC机的网卡。
2、将路由器的eth0/0口IP地址设为；PC机的IP地址设为。将要升级的IOS映象文件拷贝到相关的目录中，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。
3、通过set 命令查看设置参数
QUOTE:
? ???rommon 2 > set
? ???PS1=rommon ! >
? ???BOOT=
? ???BSI=0
? ???RET_2_RTS=
? ????=0
4、在 rommon 状态下输入：（注意大小写）
QUOTE:
? ???rommon 3 >IP_ADDRESS＝路由器的ip地址)
? ???rommon 4 >IP_SUBNET_MASK＝（路由器的掩码）
? ???rommon 5 >DEFAULT_GATEWAY＝（缺省网关，是pc机的ip地址）
? ???rommon 6 >TFTP_SERVER＝（是pc机的ip地址）
? ???rommon 7 >TFTP_FILE＝C2600-I-MZ.122-11.BIN? ? （上传ios文件的名称）
? ???rommon 8>sync? ?? ?? ?? ?? ?? ?? ?? ?? ???（保存参数设置）
? ???rommon 9 >set? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?（查看）
? ???rommon 10 > set
? ???PS1=rommon ! >
? ???BOOT=
? ???TFTP_FILE=C2600-I-MZ.122-11.BIN
? ???BSI=0
? ???RET_2_RTS=
? ????=0
? ???rommon 11 >tftpdnld
执行tftpdnld命令进行ios升级，有时可能会报错或命令不执行，这时只要用sync命令保存设置后，重新启动路由器（最佳关掉电源再开机）后，再执行tftpdnld命令就能了。
QUOTE:
? ???rommon 11 >tftpdnld（传送文件）出现提示选择y
? ???TFTP_FILE: C2600-I-MZ.122-11.BIN
? ???Invoke this command for disaster recovery only.
? ???WARNING: all existing data in all partitions on flash will be lost!
? ???Do you wish to continue? y/n:??[n]:??y
? ???!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
? ???…
? ???!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
? ???File reception completed.
? ???Copying file C2600-I-MZ.122-11.BIN to flash.
? ???Erasing flash at 0x607c0000
? ???program flash location 0x605b0000
? ???rommon 13 >
? ???在rommon 13 >提示符下键入reset，或重新启动路由器（power-cycle）,进入正常引导状态，即：
? ???Router>
笔者在Cisco2500、2600、7200等系列路由器上均实际操作过，以上为在Cisco2610路由器上实际操作捕捉或截屏，所配地址只是特例，大家可根据实际需要予以修改。最后建议：大家在作正常路由器系统升级时，为防止不正确操作等引起的升级失败，请先把路由器原有的系统备份下来。
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