1 开机流程
1.Power On Self Test 2.Rom中的bootstrap从Flash中寻找IOS 3.IOS从nvram中找startup-config,若找到，则将其复制到ram中，调用running-config 4.若未找到，则查找tftp服务器（一般找不到），继而启动setup-mode(可修改密码)
2 配置寄存器
路由器中的配置路由器configuration register用于设置路由器启动后的运行、检测方式，存放于NVRAM,在config模式和rammon模式下可以修改，改后须存:#copy running-config startup-config，重启后才能有效。
路由器配置寄存器的各bit位说明： Bit Number | Hex | Meaning | 00-03 | 0x0000-0x000F | Boots Field Parameters: · 0x0000 - Stays at the system bootstrap prompt. · 0x0001 - Boots the first system image in onboard Flash memory (EPROM). · 0x0002-0x000F- Specifies a default netboot filename.
Enables boot system commands that override the default netboot filename. | 06 | 0x0040 | · Ignore NVRAM contents | 07 | 0x0080 | · Disable boot messages | 08 | 0x0100 | · Break disabled | 10 | 0x0400 | · IP broadcast with all zeros | 5,11,12 | 0x0020, 0x0800, 0x1000 | · Console line speed | 13 | 0x2000 | · Boots default ROM software if network boot fails | 14 | 0x4000 | · IP broadcasts do not have net numbers | 15 | 0x8000 | · Enables diagnostic messages · Ignores NVRAM contents |
按照各bit位的说明，各最终值具有以下功能： Configuration Register Setting | Router Behavior | 0x102 | · Ignores break · 9600 console baud | 0x1202 | · 1200 baud rate | 0x2101 | · Boots into bootstrap · Ignores break · Boots into ROM if initial boot fails · 9600 console baud rate | 0x2102 | · Ignores break · Boots into ROM if initial boot fails · 9600 console baud rate default value for most platforms | 0x2120 | · Boots into ROMmon · 19200 console speed | 0x2122 | · Ignores break · Boots into ROM if initial boot fails · 19200 console baud rate | 0x2124 | · NetBoot · Ignores break · Boots into ROM if initial boot fails · 19200 console speed | 0x2142 | · Ignores break · Boots into ROM if initial boot fails · 9600 console baud rate · Ignores the contents of Non-Volatile RAM (NVRAM) (ignores configuration) | 0x2902 | · Ignores break · Boots into ROM if initial boot fails · 4800 console baud rate | 0x2922 | · Ignores break · Boots into ROM if initial boot fails · 38400 console baud rate | 0x3122 | · Ignores break · Boots into ROM if initial boot fails · 57600 console baud rate | 0x3902 | · Ignores break · Boots into ROM if initial boot fails · 2400 console baud rate | 0x3922 | · Ignores break · Boots into ROM if initial boot fails · 115200 console baud rate |
3 重置密码
默认情况下，寄存器值为0x2102,若需修改密码，则改为0x2142。
1 在路由器开机30S内，按住Ctrl+Pause Break组合键,进入COMMON模式。
2 rommon 1>confreg 0x2142 3 rommon 2>reset 4 重启后输入no或ctrl+c跳过初始化程序，直接进入路由器 5 router(config)#enable secret xxx（重新设置密码） 6 router(config)#config-register 0x2102 （还原寄存器值） 7 router#copy running-config startup-config （保存配置信息）
tga:南宁ccna培训 南宁ccnp培训 | 
