The running configuration file in a Cisco IOS device contains the current configuration settings that are active. This includes interface configurations, routing protocol configurations, and more.
This file is different than the startup configuration file. The startup configuration file contains the initial settings when the device is rebooted or powered on.
The running configuration can be viewed using several commands, including show running-config and show startup-config. You can also view the running configuration by using a terminal connection such as Putty or Cisco Device Manager.
Changing the running configuration requires an additional step of committing the change. This is done by using the command: configure confirm.
There are several ways to delete or clear the running configuration file. Understanding how to do this is important in situations where there is a faulty config setting that needs to be reset to default or where there is need to revert back to the startup config settings.
This article will discuss each way to delete or clear the running configuration file and when each should be used.
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1) Reboot
A very simple way to clear out the running config is to just reboot your device! Of course, this will result in your device having no configured settings and being at a starting point again, so use with caution.
This should only be done if you know that there are no changes that need to be applied and confirmed by issuing a confirm replace boot command.
A good time to use this method is right before doing a software upgrade so that you do not have to go through confirming all of your initial settings again after installing the new update.
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Another way to remove any config from a device is by deleting each line individually from the running config file.
This takes some time but can be very precise in which lines are removed.
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confirm erase configure all
This will completely erase any changes made in either NVRAM, CFG, BND files, or any other manually inputted commands.It will take some time for it complete depending on how many lines are present in those files.
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The running configuration file stores the current running settings of a Cisco IOS device
When a configuration is changed, it has to be activated for the new settings to take effect. This process can be done manually or dynamically.
Manual activation requires the user to enter the command:
This will update the running configuration with the new configuration file. The IOS device will then apply these changes and configure the device according to the new settings.
The dynamic way of activating the changes is by using a protocol such as Cisco’s Border Gateway Protocol (BGP). When BGP receives an update that changes the routing table, it automatically enters into operation a config synchronization command that updates the running configuration file.
When either of these methods are used, they are stored in the running configuration file. If you look at your IOS device, you can see that there are more lines in the running configuration than in the configuration file.
The startup configuration file stores the default startup settings of a Cisco IOS device
A configuration file is a set of commands that describe the configuration of a device. These commands are either enabled or disabled, and some require other commands to be enabled before they can be used.
A configuration file can be in several formats, but the most common ones are text files with extension .txt or .cfg. While a text file can be modified in any text editor, a config file requires a specific editor to edit it.
The advantage of having a config file is that it is easier to backup and transfer it to other devices. A .txt file can easily be copied and pasted into another device, whereas having to transfer an internal database may not work as smoothly.
On all modern Cisco IOS devices (those that use the Cisco Configuration Manager), there is an internal database that stores the current running-configuration. When you make changes to the running-configuration, they are saved in this database; however, when you reboot the device, the running-configuration reverts back to the default startup configuration.
The running configuration file can be viewed or modified using the show run command
The show run command is a way to view the current configuration of a Cisco IOS device. This command allows you to see what settings are applied to the device at that moment.
You can also use this command to copy and paste the current configuration into a new config file. This can be done using the terminal interface or through a software like Cyberduck.
The running configuration file is stored in RAM, which means it will be lost when the device reboots or loses power. The file can also be viewed with the show run command, so it is public knowledge.
You should always verify your configured settings in your running configuration file with the show run command before applying any changes with the config terminal enter command. This is due to possible mistakes in typing the commands and confirming them.
The startup configuration file can be viewed or modified using the show start command
The running configuration file is automatically saved every time a user exits or changes the configuration of the device using the configure terminal command.
This means that any changes made to the device configuration by a user will be automatically saved and will become part of the running configuration.
Any changes made to the running configuration require a reload or restart of the device for them to take effect. This is why it is important to know if you have made any mistakes in the configuration while editing it.
The running configuration can be viewed using either the show run or show startup-config commands. The latter returns only the starting (start) and active (active) configurations. Both of these commands can be used in both privileged and non-privileged mode.
Only one running configuration file can be present at any given time on a device.
