cisco设备基础知识（自我学习贴）

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1：配置user mode的password

          配置passord加密存储
        Switch(config)#service password-encryption

          配置console端口登录的password
        Switch(config)#line console 0
        Switch(config-line)#password cisco
        Switch(config-line)#login

          配置telnet登录的password
        Switch(config)#line vty 0 15
        Switch(config-line)#password cisco
        Switch(config-line)#login

2：配置privilege mode的password

        Switch(config)#enable secret cisco

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cisco device hardware components

1：ROM

     全称：Read-only memory
     内容：cisco设备的firmware
     作用：POST（power on self  test），设备自检
             bootstrap device，引导设备启动，选择要启动的ISO和配置文件
             ROM monitor，在设备启动的过程中按下CTRL+BREAK进入ROM监控模式，可在此模式下恢复密码
             Mini-IOS，ISO无法引导，选择flash中其他的ISO引导

2：RAM

     内容：运行的IOS image，激活的配置文件，各种表（路由表，arp表 etc），缓存信息
     作用：从flash中读取需要的信息，维持设备正常运行，存储设备的运行状态信息

3：NVRAM

     内容：配置文件
     作用：存储设备的配置文件，供设备下次启动调用使用

4：flash

     内容：设备启动的IOS
     作用：存储设备的iOS，供设备启动调用使用

1. tsw1#dir flash:
   
2. Directory of flash:/
   
3. 
   
4.     3  -rwx        2072   Mar 1 1993 08:00:57 +08:00  multiple-fs
   
5.     4  -rwx        7956   Mar 1 1993 09:10:46 +08:00  startup.config
   
6.     5  -rwx     6935268  May 23 2008 00:19:06 +08:00  c2960-lanbasek9-mz.122-44.SE1.bin
   
7.     6  -rwx         676   Mar 1 1993 08:00:52 +08:00  vlan.dat
   
8.     7  drwx         128  Feb 24 2010 14:57:10 +08:00  c2960-lanbase-mz.122-35.SE5
   
9.   626  -rwx     8471143  Aug 31 2011 16:34:43 +08:00  c2960-lanbasek9-mz.122-52.SE.bin
   
10.   627  -rwx        7847   Mar 5 1993 09:09:00 +08:00  startupconfig
    
11.   624  -rwx           5  Aug 31 2011 16:41:40 +08:00  private-config.text
    
12.   628  -rwx        8270  Aug 31 2011 16:41:40 +08:00  config.text
    
13. 
    
14. 32514048 bytes total (13966336 bytes free)
    
15. tsw1#dir nvram:
    
16. Directory of nvram:/
    
17. 
    
18.    54  -rw-        8270                    <no date>  startup-config
    
19.    55  ----           5                    <no date>  private-config
    
20.     1  ----          24                    <no date>  persistent-data
    
21.     2  -rw-           0                    <no date>  ifIndex-table
    
22. 
    
23. 65536 bytes total (55161 bytes free)

复制代码

yzkarchive

How to recovery the cisco device password

1：Restart the cisco device，重启cisco设备

2：Use CTRL+BREAK into the ROMMON mode，同时按下CTRL+BREAK，进入ROM监控模式

3：Input the "confreg 0x2142" command，输入“confreg 0x2142” <启动只加载IOS，不加载配置文件>

4：Input the "boot" command，输入“boot”。

修改密码完成后，在全局模式下输入：switch（config）#config-register 0x2102，然后保存配置到NVRAM中（多谢版主提醒）

ssffzz1

改好密码后02142要改回来。别只帖一半。

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Backup the configuration file

保存RAM中的配置信息到NVRAM中：copy running-config startup-config

保存NVRAM中的配置信息到tftp服务器中：copy startup-config tftp

保存tftp服务器的配置信息到NVRAM中：copy startup-config tftp

其中，把配置文件从tftp服务器或者NVRAM中读入RAM中，配置信息是一个合并的过程，而不是完全的覆盖，添加新增信息，修改不同信息，保留不涉及信息。

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交换机的转发机制

1：Store and Forward

     Pull the entire frame into the port buffer, check the CRC.

2：Cut through

     Only read part of the frame until the destination MAC, then forward the frame and continue to pull the frame into port buffer.
     when the bad frame reached the threshold, tranfer the module to store-and-forward

3：fragment free

      Make sure the least frame is 64 bytes, only check the first 64 bytes

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The function of switch

1: Learning

    The switch compare the source MAC of the frame with CAM table of the switch, if the CAM table without the MAC, record it.
    The record just like that:
          4011    0800.56c8.160d    DYNAMIC     Gi0/24

2: Forwarding

    If the destination MAC is a broadcast address, forward the frame from all the ports exception the input port
    If the destination MAC is a multicast, deal with the multicast to unicasts, then forward it
    If the destination MAC is a unicast, and the destination MAC in the CAM table, forward it according the CAM table, If the destination MAC isn't in the CAM table, broadcast it.

3: Removing the layer-2 loop

    According the mechanism of forwarding, forward the broadcast frame to all ports exception the input port, if there have three switch connection with each other, there will be a loop. Another the have more than one cable between two switches in the same vlan, there has a loop olso.

    The spanning tree protocol is to remove the layer-2 loop.

    According the switch ID the select the root switch, the swith ID is made up of two components:
        the priority of the switch, the default priority is: 32768.
        the MAC address of the switch.
    The root switch has the maximum age time: 20 seconds

    If there more than one cable between the switches in a vlan, the root port is needed.
        choose the lowest cast path to the root
        choose the lowest priority switch to the root
        choose the port witch lowest priority
        choose the lowest-number physical port

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The operation of cisco configuration file

CMD:
         dir        list the file
         copy    copy file from one to another
         delete  delete a file
         more    Display the content of a file

zenglei0115

呵呵，不错，温故而知新