拓撲圖：
- 1 配置任意特權加密密碼,並保存
Router>enable
Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname R1
R1(config)#interface g 0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#enable secret asdf
%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up
R1(config)#exit
R1#
%SYS-5-CONFIG_I: Configured from console by console
R1#wr
Building configuration...
[OK]
R1#
-
2 重啓路由器reload
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3 在加載系統過程中， 使用 Ctrl+Break 鍵或者 Ctrl+C 鍵，修改 confreg寄存器的值，使路由器繞過配置文件進入系統
rommon 1 > help boot boot up an external process confreg configuration register utility dir list files in file system help monitor builtin command help reset system reset set display the monitor variables tftpdnld tftp image download unset unset a monitor variable rommon 2 > confreg 0x2142 rommon 3 > reset - 4 此時已可以不輸入密碼即可進入系統，這時我們重新配置密碼。配置密碼完成後，修改confreg寄存器的值，引導系統正常啓動。
Router>en
Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname R1
R1(config)#enable sec
R1(config)#enable secret 123abc
R1(config)#config-register 0x2102
R1(config)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console
R1#wr
Building configuration...
[OK]- 5 最後重啓reload