Advantages of configuring registers in Cisco routes

The advantages of configuring registers in Cisco routes are of great interest to you. Before giving you a detailed introduction to the advantages of configuring registers in a Cisco Route, let's first take a look at the basic process of configuring registers and then compare the advantages and disadvantages of the following methods.

All Cisco router devices have a 16-bit software register in NVRAM, which is also called a management configuration register. Many parameters related to router operation are recorded in this configuration register. In fact, if we compare it to the manager of a Cisco router, it will not go too far.

1. Configure the physical structure of registers

The physical structure of the configuration register is actually very simple, that is, 16 digits in NVRAM. The 16 bits in the configuration register are 15 bits and 14 bits in place from left to right. Each bit stores a binary value, that is, either 0 or 1. When a vro is started, it judges the values of these bits and then takes corresponding actions.

By default, the configuration register is set to load IOS software from the flash memory, and search for and load the configuration file from the NVRAM memory. At this time, the value of this configuration register is 13th, the eighth bit, the first bit is 1, and the other bit is 0. If the network administrator wants to manage a Cisco router device, it is necessary to understand the meaning of the various devices in this configuration register.

In practice, it is difficult to remember the binary value of the sixteen bits. Our network administrator often prefers to use hexadecimal values to represent the binary settings of the sixteen-digit number. For example, 0x2102 indicates 13th, eighth, first, and other bits are 0. The preceding 0x indicates that the number is in hexadecimal format.

However, the conversion between hexadecimal and binary can be achieved through professional converters or manual conversions. For specific conversion methods, refer to some technical manuals. The author is not able to expand here. However, the author is still like Luo Han. In fact, there is a calculator tool in the Microsoft Operating System. With this tool, you can easily convert hexadecimal to binary values.

First, select the hexadecimal value in the hexadecimal option, and then input the hexadecimal value, such as 2102. Note that you do not need to enter the previous hexadecimal identifier. Then select binary. In this case, the calculator will convert the hexadecimal value directly to the binary value. But pay attention to this number.

If you want to convert a binary value to a hexadecimal value, perform the opposite operation. In the configuration register, the leftmost bit is the 15th bit, And the rightmost bit is the zeroth bit. That is to say, it does not start with one. This may be misunderstood at the beginning of the management of configuration registers. In addition, our network administrator also needs to understand the meanings of some common configurations. This will play a significant role in future troubleshooting.

For example, in the deposit configurator, the zeroth to the third digit, and the four-digit binary indicate the startup sequence of the vro, which is called the start field. If the network administrator wants to use the ROM monitoring mode when the router is started, set the configuration register value to 2100 (hexadecimal), that is, set the number of the following digits to zero. If the network administrator wants to start the IOS image file stored in the ROM, set the configuration register value to 2101 (hexadecimal), that is, change the last four digits to 0001. And so on.

To manage Cisco routers, the network administrator must understand the meaning of common codes. However, it is difficult to remember all these codes. It is also very difficult for me to remember. However, I am clever enough to make a small table of what these codes represent. When necessary, just take a look at it. In addition, another important function of the storage Configurator is to use it to restore the vro password. This is especially useful when the network administrator accidentally forgets the vro password.

2. How can I view the current configuration value of a vro?

If you want to modify the register configuration, you first need to know the current value of the configurator. Otherwise, the configuration cannot be changed. There is an existing command in the IOS software of the Cisco router to help the network administrator display the value in the configuration register. This command is Show Version.

This command displays information about the router IOS version, system hardware configuration, configuration file name and source, and startup image file. At the end, it displays the current value of the router register configuration. However, it is represented by hexadecimal notation. If necessary, the network administrator can use a calculator to convert the data. We can also see the importance of carrying a register configurator code table with you.

3. When do I need to change the register configuration value?

Although the configuration register can control the running idea of the vro, we do not recommend that you directly change the configuration register to maintain the vro. This is equivalent to the use of management software. If you can maintain data on the application interface, you can maintain the data in the application rather than directly making changes to the database.

Because data modification in applications often adds some audit conditions to ensure data consistency. Therefore, I believe that, unless there are special needs, do not directly change the value of the configuration register. Under normal circumstances, if you have the following requirements, you can try to change the value of the configuration register.

If the network administrator needs to force the system to enter ROM monitoring mode, you can change the value of the configuration register to 2100. For example, when the network administrator needs to select the boot source and the default startup file name, the configuration register value can be set to 2102. The above are all hexadecimal values.

In addition, if the network administrator wants to control the broadcast address, enable or disable the interrupt function (required to restore the vro password) set the baud rate of the console terminal, load the operating software from the Rom, or enable the startup server from the TFTP simple File Transfer Protocol by modifying the configuration register value.

In other words, if there are other methods besides modifying the value of the configuration register to meet a certain requirement, it is best not to modify the configuration register. Unless you have strong confidence in your professional skills. In addition, you must understand the current value of the storage configurator when modifying the value of the storage configurator.

If necessary, if the network administrator finds more problems after modifying the register configuration value, it needs to be restored. In addition, the modification of the storage Configurator is often temporary. Or it is only for troubleshooting purposes. After troubleshooting, the network administrator often needs to restore the previous settings. Therefore, it is necessary to understand the current configuration of the configuration register.

4. modify the configuration register value

In a Cisco router, we can use the config-register command to change the value of the configuration register. Basically all Cisco routers support this command. However, when executing this command, pay attention to the following points.

First, in the IOS software of the router, The hexadecimal value is used to represent the value in the configuration register. That is to say, if we want to change the value of the configuration register to 0x2101, we need to use the command config-register 0x2101. That is to say, add a hexadecimal sign before the number. Otherwise, the system will not accept it.

Second, the configuration register value cannot be immediately modified. This configuration takes effect only after the router is reloaded. For example, if the original value of the configuration register is 0x2101, after we change it to 0x2100, when we use the Show Version command to view the current Register configuration value, it still displays 0x2101, instead of the modified 0x2100.

This is mainly because the configuration register must be reloaded to take effect. The modified configuration is invalid before reload is performed. The Show Version displays the current configuration, so the changed content cannot be displayed. That is to say, you must use the Show Version command to display the modified value after the router is reloaded.

5. Use the configuration register to restore the vro Password

When the network administrator is blocked from the vro because he forgets the vro password, we can modify the configuration register value to restore the vro password. By default, the value of the configuration register is 0X2102, which means to search for and load the router configurations stored in NVRAM.

If you want to restore the vro password, you need to change the value of the configuration register to 0X2142, that is, change the binary value of the sixth bit to 1. When the vro restarts after the change, it will tell the vro to ignore the configuration file in NVRAM. This is the basic principle of vro password recovery. Of course, different IOS software versions may have different operation methods, but the configuration register is modified in the same way.

The above is a little bit about the configuration register modification. However, unless the specific items listed above are involved, do not modify the value of the configuration register at will. In addition, before modification, it is best to use the relevant commands to view the value of the configuration register, and use the notes recorded. When a router is faulty due to configuration errors, you can set the register configuration value to the previous value.