清空路由器所有配置，重启

Router#erase startup-config

Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]

[OK]

Erase of nvram: complete

%SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram

Router#reload

Proceed with reload? [confirm]

设置密码，并保存配置

Router>en

Router#conf t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#enable password 123

Router(config)#exit

Router#

%SYS-5-CONFIG_I: Configured from console by console

Router#wr

Building configuration...

[OK]

密码恢复

关闭路由器电源并重新开机，在路由器启动时，按【Ctrl+Break】键中断路由器的启动过程，进入rommon 模式。

rommon 1 > confreg 0x2142

rommon 2 > boot
......

         --- System Configuration Dialog ---

Continue with configuration dialog? [yes/no]: no

此时已可以直接进入特权模式，将NVRAM中的配置复制到RAM中

Router>

Router>en

Router#copy startup-config running-config

Destination filename [running-config]? 

429 bytes copied in 0.416 secs (1031 bytes/sec)

%SYS-5-CONFIG_I: Configured from console by console

重新设置密码，保存配置，重启。

Router#conf t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#enable password 123456

Router(config)#conf

Router(config)#config-register 0x2102

Router(config)#exit

%SYS-5-CONFIG_I: Configured from console by console

Router#wr

Building configuration...

[OK]

Router#reload

Proceed with reload? [confirm]