Step by step teach you how to configure a Cisco Router

Many people may not have a special understanding of Cisco router configuration, so I have studied the detailed knowledge of Cisco router configuration. I will share it with you here, hoping it will be useful to you. Have you ever encountered a situation where you have modified the Cisco router or vswitch and need to remove the modifications? There are many ways to do this, but which method is the simplest and safest? Restarting a vro or vswitch is not the correct answer. In fact, you only need to use a simple command, but the effect is much better.

Suppose you have implemented some modifications on a vro and generated a huge Cisco router configuration file. You may have noticed that something is wrong while making the changes, and the expected new functions did not work during the test. What you want now is to restore everything to its original state and then start from scratch. How can we achieve this? You have several options.

If you have not saved the Cisco router configuration, simply restart the router. This is useful, but you certainly do not want to have to restart a product router. In addition, when there is no need, why do you restart a vro and sit down and wait? You can also use the copy startup-config running-config command. However, what this command does may not be as you think. It only combines the commands in startup-config with those in running-config.

If there is a conflict, it will leave the command in running-config. As a result, what you get is a mixture of Cisco router configurations. In addition, it may also produce some unexpected results due to the mixing of the old configuration and the modified configuration, and eventually lead to some vro shutdown or paralysis.

How can we restore the Initial startup-config configuration without stopping services? The answer to this question is the "configure replace" command. This command compares running-config with the configuration to be replaced. It will identify the differences between the two Cisco router configurations and then only implement these different parts. This command does not affect the configurations of Cisco routers that have not been changed, and does not cause any shutdown.

In general, you can replace the current configuration of running-config by using the startup-config initial configuration stored in the vronvnvram ). To do this, you need to execute the following command: configure replace nvram: startup-config. However, the last parameter can be any valid config file, as long as it is in an acceptable Cisco ios url format. For example, the actual storage location of the config file can be on a TFTP, FTP, HTTP, RCP or SCP server. In this case, the command may change to the following: configure replace tftp: // 192.168.1.107/config-bu.

Table A provides A basic example of using the Configure replace command. First, I disabled my FastEthernet4 interface, and then I used the configure replace nvram: startup-config command to set startup-configuration with my start point) replace the currently set running-configuration ). Although this is a simplified example, it shows how the command works. The Configure replace command is very useful-it can often minimize the downtime and restore you to the starting point before the change.