1.对于Catalyst 2900/3500XL系列来说:
拔下交换机的电源线,然后按住交换机的Mode按钮,再重新插上交换机的电源线.直到端口Port 1x的LED熄灭之后释放Mode按钮.
2.对于Catalyst 2940/2950L系列来说:
拔下交换机的电源线,然后按住交换机的Mode按钮,再重新插上交换机的电源线.直到STAT的LED熄灭之后释放Mode按钮.
3.对于Catalyst 2955系列来说:
Catalyst 2955没有没有外部的Mode按钮,因此就不能使用之前的那种方法来进行密码恢复.在交换机启动时,对于Windows系列的PC,按下Ctrl+Break键;对于UNIX系列的工作站,按下Ctrl+C.如下:

C2955 Boot Loader (C2955−HBOOT−M) Version 12.1(0.0.514), CISCO DEVELOPMENT TEST
VERSION
Compiled Fri 13−Dec−02 17:38 by madison
WS−C2955T−12 starting...
Base ethernet MAC Address: 00:0b:be:b6:ee:00
Xmodem file system is available.
Initializing Flash...
flashfs[0]: 19 files, 2 directories
flashfs[0]: 0 orphaned files, 0 orphaned directories
flashfs[0]: Total bytes: 7741440
flashfs[0]: Bytes used: 4510720
flashfs[0]: Bytes available: 3230720
flashfs[0]: flashfs fsck took 7 seconds.
...done initializing flash.
Boot Sector Filesystem (bs:) installed, fsid: 3
Parameter Block Filesystem (pb:) installed, fsid: 4
/---接下来交换机会在15秒内自动启动,
等出现该信息之后,按下Ctrl+Break键或Ctrl+C键----/
The system has been interrupted prior to initializing the flash file system to finish
loading the operating system software:
flash_init
load_helper
bootswitch:

接下来输入flash_init命令:

switch:flash_init
Initializing Flash...
flashfs[0]: 143 files, 4 directories
flashfs[0]: 0 orphaned files, 0 orphaned directories
flashfs[0]: Total bytes: 3612672
flashfs[0]: Bytes used: 2729472
flashfs[0]: Bytes available: 883200
flashfs[0]: flashfs fsck took 86 seconds
....done Initializing Flash.
Boot Sector Filesystem (bs:) installed, fsid: 3
Parameter Block Filesystem (pb:) installed, fsid: 4
switch:

接着输入load_helper命令:

switch:load_helper
switch:

再输入dir flash:命令显示交换机的文件系统:

switch:dir flash:
Directory of flash:/
2 −rwx 1803357 <date> c3500xl−c3h2s−mz.120−5.WC7.bin
4 −rwx 1131 <date> config.text
5 −rwx 109 <date> info
6 −rwx 389 <date> env_vars
7 drwx 640 <date> html
18 −rwx 109 <date> info.ver
403968 bytes available (3208704 bytes used)
switch:
把配置文件重命名:

switch:rename flash:config.text flash:config.old
switch:

输入boot命令启动交换机:

switch:boot
Loading "flash:c3500xl−c3h2s−mz.120−5.WC7.bin"...###############################
################################################################################
######################################################################
File "flash:c3500xl−c3h2s−mz.120−5.WC7.bin" uncompressed and installed, entry po
int: 0x3000
executing...

不进入setup模式:

−−− System Configuration Dialog −−−
At any point you may enter a question mark '?' for help.
Use ctrl−c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.
Continue with configuration dialog? [yes/no]: n

进入特权模式,恢复原始的配置文件:

Switch#rename flash:config.old flash:config.text
Destination filename [config.text]
Switch#

把配置文件保存在内存里:

Switch#copy flash:config.text system:running−config
Destination filename [running−config]?
1131 bytes copied in 0.760 secs
Switch#

进入全局配置模式,取消密码设置:

Switch(config)#no enable secret

保存配置:

Switch#write memory
Building configuration...
[OK]
Switch#

4.对于Catalyst 3550/3750系列来说:
1.通过带有支持Xmodem协议的超级终端程序的PC连接到交换机的console口,把波特率设置为9600.
2.拔掉交换机的电源.
3.按下交换机上的Mode按钮,与此同时,重新插上交换机的电源线.当交换机端口1X上的LED熄灭后可以松开Mode按钮1到2秒.之后将显示一些指示信息:

The system has been interrupted prior to initializing the flash file system. The following
commands will initialize the flash file system, and finish loading the operating system
software:
flash_init
load_helper
boot
switch#
4.初始化flash文件系统:
switch#flash_init
5.加载帮助文件:
switch#load_helper
6.显示闪存里的内容:
switch#dir flash:
7.重命名配置文件:
switch#rename flash:config.text flash:config.text.old
8.启动系统,并且如果提示进入setup模式,输入N:
switch#boot
Continue with the configuration dialog? [yes/no]: N
9.进入特权模式,把配置文件名恢复为原始文件名:
Switch#rename flash:config.text.old flash:config.text
10.把配置文件写进内存:
Switch#copy flash:config.text system:running-config
Source filename [config.text]?
Destination filename [running-config]?
11.进入全局配置模式更改密码:
Switch(config)#enable secret {password}
12.退出,并保存到startup-config文件里:
Switch(config)#copy running-config startup-config

其实有的时候硬件安全比软件安全还要重要些.不然人人都抗个本本,.连根线到console口去恢复密码了-_-