Cisco3845路由器登陆问题

Cisco3845路由器，一般使用在大中型分支机构中，路由器出厂默认安装了Cisco SDM模块（路由器及安全配置工具），这样，在登陆时就会出现如下提示：

———————————————————————–
Cisco Router and Security Device Manager (SDM) is installed on this device.
This feature requires the one-time use of the username “cisco”
with the password “cisco”. The default username and password have a privilege level of 15.

Please change these publicly known initial credentials using SDM or the IOS CLI.
Here are the Cisco IOS commands.

username <myuser> privilege 15 secret 0 <mypassword>
no username cisco

Replace <myuser> and <mypassword> with the username and password you want to use.

For more information about SDM please follow the instructions in the QUICK START
GUIDE for your router or go to http://www.cisco.com/go/sdm
———————————————————————–
User Access Verification

Username:

使用用户名和密码都为cisco来登陆路由器，然后再添加用户，再使用no username cisco命令将默认用户cisco删除，如果你没有创建用户，而直接将cisco用户删除再保存了配置，下次进入后使用cisco路由器就不能登陆了。

经过查看路由器配置，con和vty口的配置如下：

line con 0
login local
line aux 0
line vty 0 4
access-class 23 in
privilege level 15
login local
transport input telnet
line vty 5 15
access-class 23 in
privilege level 15
login local
transport input telnet

发现是在con和vty口上使用了login local认证，这样就会使用cisco sdm来认证，所以，这里只需将login local修改为login，就可以跳过cisco sdm的认证，如下：

enable password 15 cisco
!
line con 0
password cisco
login
line aux 0
line vty 0 4
password cisco
login
transport input telnet
line vty 5 15
password cisco
login
transport input telnet

现在进不去路由器，只能通过修改enable密码的方法来进入路由器，再进行以下的修改：

1、将电脑与路由器的console口相连，启动路由器，按下[ctrl]+[break]，如下，出现rommon命令提示符：

System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2006 by cisco Systems, Inc.

System Bootstrap, Version 12.4(13r)T11, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2008 by cisco Systems, Inc.

Total memory size = 256 MB – DIMM0 = 256 MB, DIMM1 = 0 MB
c3845 platform with 262144 Kbytes of main memory
Main memory is configured to 72/0(dimm 0/1) bit mode with ECC enabled
Upgrade ROMMON initialized

monitor: command “boot” aborted d
monitor: command “boot” aborted due to user interrupt
rommon 1 >

2、输入confreg，如下，记录下0x2102，do you wish处选择no

rommon 1 > confreg
Configuration Summary
(Virtual Configuration Register: 0x2102)
enabled are:
load rom after netboot fails
console baud: 9600
boot: image specified by the boot system commands
or default to: cisco2-c3845

do you wish to change the configuration? y/n [n]:

3、通过confreg命令来修改配置寄存器的值，使路由器忽略NVRAM中的启动配置文件。输入confreg 0x2142来修改寄存器值，再输入i重启路同器，如下：

rommon 2 > confreg 0x2142
rommon 3 > i

4、启动后会进入用户exec模式，出现系统配置对话柜时输入no跳过，如下：

— System Configuration Dialog —

Would you like to enter the initial configuration dialog? [yes/no]: no
Press RETURN to get started!

5、使用enable命令进入配置模式，再使用sh run命令查看，这时会发现配置全部消失，因为这里是跳过NVRAM来启动路由器的，使用copy命令将NVRAM中的配置文件复制到现在的启动（running-config）配置文件中，

Router>en
Router#copy startup-config running-config

6、接下来对running-config配置文件进行修改，按照上面分析的，修改为：

enable password 15 cisco
!
line con 0
password cisco
login
line aux 0
line vty 0 4
password cisco
login
transport input telnet
line vty 5 15
password cisco
login
transport input telnet

这样，下次就可以直接使用cisco密码来进行认证了。

7、接下来做配置的保存工作，首先恢复配置寄存器的值0x2102，再保存配置，这里需使用write memory，完成后重启路由器，就可以使用cisco来登陆了。

Router#copy running-config startup-config
Router#configure terminal
Router(config)#config-register 0x2102
Router(config)#end
Router#write memory
Router#reload