Lesson No. 8 Cisco Router Configuration Files

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Cisco Router configuration files hold the commands to configure the router. There are two main copies of Cisco Router configuration file. The configuration file where router stores the configuration changes when the router is up and running is called the "running-config" file. The running configuration file stores the configuration changes made while the router is up and running. The "running-config" file is stored in RAM. The "running-config" file is NOT persistent, which means that the changes made in the "running-config" while the router is running are not retained after a reboot. You can back up, or save, "running-config" file to either NVRAM or a TFTP (Trivial File Transfer Protocol) server.

A persistent copy of Cisco Router configuration file is called as "startup-config" file. The "startup-config" file is kept in NVRAM and the contents of the "startup-config" file are retained after a reboot. To save the changes of "running-config" file to "startup-config", run the following IOS command.

OmniSecu03# copy running-config startup-config 

The "running-config" can also be saved in a TFTP (Trivial File Transfer Protocol) server if you have a TFTP (Trivial File Transfer Protocol) server in your network. To save "running-config" file to a TFTP (Trivial File Transfer Protocol) server, run the following IOS command.

OmniSecu03# copy running-config tftp 

Remember, "startup-config" is a persistent copy of configuration file, which is kept normally in NVRAM.

Location of Configuration Files

Configuration files are stored in the following locations:

•The running configuration is stored in RAM.

•On all platforms except the Class A Flash file system platforms, the startup configuration is stored in nonvolatile random-access memory (NVRAM).

•On Class A Flash file system platforms, the startup configuration is stored in the location specified by the CONFIG_FILE environment variable (see the "Specifying the CONFIG_FILE Environment Variable on Class A Flash File Systems" section for more information). The CONFIG_FILE variable defaults to NVRAM and can be a file in the following file systems:

–nvram: (NVRAM)

–bootflash: (internal Flash memory)

–slot0: (first PCMCIA slot)

–slot1: (second PCMCIA slot)

Displaying Configuration File Information

To display information about configuration files, use the following commands in EXEC mode, as needed:

Command	Purpose
Router# show bootvar	Lists the contents of the BOOT environment variable, the name of the configuration file pointed to by the CONFIG_FILE environment variable, and the contents of the BOOTLDR environment variable.
Router# morefile-url	Displays the contents of a specified file.
Router# show running-config	Displays the contents of the running configuration file. (Command alias for the more system:running-config command.)
Router# show startup-config	Displays the contents of the startup configuration file. (Command alias for the more nvram:startup-config command.) On all platforms except the Class A Flash file system platforms, the default startup-config file usually is stored in NVRAM. On the Class A Flash file system platforms, the CONFIG_FILE environment variable points to the default startup-config file. The CONFIG_FILE variable defaults to NVRAM.

Modifying the Configuration File at the CLI

The Cisco IOS software accepts one configuration command per line. You can enter as many configuration commands as you want.

You can add comments to a configuration file describing the commands you have entered. Precede a comment with an exclamation point (!). Because comments are not stored in NVRAM or in the active copy of the configuration file, comments do not appear when you list the active configuration with theshow running-config or more system:running-config EXEC command. Comments do not display when you list the startup configuration with the show startup-config or more nvram:startup-config EXEC mode command. Comments are stripped out of the configuration file when it is loaded onto the router. However, you can list the comments in configuration files stored on a File Transfer Protocol (FTP), remote copy protocol (rcp), or Trivial File Transfer Protocol (TFTP) server.

When you configure the software using the CLI, the software executes the commands as you enter them. To configure the software using the CLI, use the following commands beginning in privileged EXEC mode:

	Command	Purpose
Step 1	Router# configure terminal	Enters global configuration mode.
Step 2		Enter the necessary configuration commands. The Cisco IOS documentation set describes configuration commands organized by technology.
Step 3	Router(config)# end or Router(config)# ^Z	Ends the configuration session and exits to EXEC mode. Note When you press the Ctrl and Z keys simultaneously, ^Z is displayed to the screen.
Step 4	Router# copy system:running-config nvram:startup-config	Saves the running configuration file as the startup configuration file. You may also use the copy running-config startup-config command alias, but you should be aware that this command is less precise. On most platforms, this command saves the configuration to NVRAM. On the Class A Flash file system platforms, this step saves the configuration to the location specified by the CONFIG_FILE environment variable (the default CONFIG_FILE variable specifies that the file should be saved to NVRAM).

Copying a Configuration File from the Router to a TFTP Server

In some implementations of TFTP, you must create a dummy file on the TFTP server and give it read, write, and execute permissions before copying a file over it. Refer to your TFTP documentation for more information.

To copy configuration information on a TFTP network server, use the following commands in the EXEC mode, as needed:

Command	Purpose
Router# copy system:running-config tftp:[[[//location]/directory]/filename]	Copies the running configuration file to a TFTP server.
Router# copy nvram:startup-config tftp:[[[//location]/directory]/filename]	Copies the startup configuration file to a TFTP server.

Copying a Configuration File from the Router to an rcp Server

To copy a startup configuration file or a running configuration file from the router to an rcp server, use the following commands beginning in privileged EXEC mode:

	Command	Purpose
Step 1	Router# configure terminal	(Optional) Enters global configuration mode.
Step 2	Router(config)# ip rcmd remote-username username	(Optional) Changes the default remote username.
Step 3	Router(config)# end	(Optional) Exits global configuration mode.
Step 4	Router# copy system:running-config rcp:[[[//[username@]location]/directory]/filename] or Router# copy nvram:startup-config rcp:[[[//[username@]location]/directory]/filename]	Specifies that the router running configuration file be stored on an rcp server. or Specifies that the router startup configuration file be stored on an rcp server.

Copying a Configuration File from the Router to an FTP Server

You can copy a configuration file from the router to an FTP server.

Understanding the FTP Username and Password

The FTP protocol requires a client to send a remote username and password on each FTP request to a server. When you copy a configuration file from the router to a server using FTP, the Cisco IOS software sends the first valid username it encounters in the following sequence:

1. The username specified in the copy EXEC command, if a username is specified.

2. The username set by the ip ftp username global configuration command, if the command is configured.

3. Anonymous.

The router sends the first valid password it encounters in the following sequence:

1. The password specified in the copy command, if a password is specified.

2. The password set by the ip ftp password command, if the command is configured.

3. The router forms a password username@routername.domain. The variable username is the username associated with the current session,routername is the configured host name, and domain is the domain of the router.

The username and password must be associated with an account on the FTP server. If you are writing to the server, the FTP server must be properly configured to accept the FTP write request from the user on the router.

If the server has a directory structure, the configuration file or image is written to or copied from the directory associated with the username on the server. For example, if the system image resides in the home directory of a user on the server, specify that user name as the remote username.

Refer to the documentation for your FTP server for more information.

Use the ip ftp username and ip ftp password global configuration commands to specify a username and password for all copies. Include the username in the copy EXEC command if you want to specify a username for that copy operation only.

Copying a Configuration File from the Router to the FTP Server

To copy a startup configuration file or a running configuration file from the router to an FTP server, use the following commands beginning in privileged EXEC mode:

	Command	Purpose
Step 1	Router# configure terminal	(Optional) Enters configuration mode from the terminal. This step is required only if you want to override the default remote username or password (see Steps 2 and 3).
Step 2	Router(config)# ip ftp username username	(Optional) Specifies the default remote username.
Step 3	Router(config)# ip ftp password password	(Optional) Specifies the default password.
Step 4	Router(config)# end	(Optional) Exits global configuration mode. This step is required only if you override the default remote username or password (see Steps 2 and 3).
Step 5	Router# copy system:running-config ftp:[[[//[username[:password]@]location] /directory]/filename] or Router# copy nvram:startup-config ftp:[[[//[username[:password]@]location] /directory]/filename]	Copies the running configuration or startup configuration file to an FTP server.

Copying a Configuration File from a TFTP Server to the Router

To copy a configuration file from a TFTP server to the router, use the following commands in EXEC mode, as needed:

Command	Purpose
Router# copy tftp:[[[//location]/directory]/filename] system:running-config	Copies a configuration file from a TFTP server to the running configuration.
Router# copy tftp:[[[//location]/directory]/filename] nvram:startup-config	Copies a configuration file from a TFTP server to the startup configuration.

Compressing the Configuration File

The service compress-config global configuration command specifies that the configuration file be stored compressed in NVRAM. Once the configuration file has been compressed, the router functions normally. When the system is booted, it recognizes that the configuration file is compressed, expands it, and proceeds normally. The more nvram:startup-config EXEC command expands the configuration before displaying it.

Before you compress configuration files, refer to the appropriate hardware installation and maintenance publication. Verify that your system's ROMs support file compression. If not, you can install new ROMs that support file compression.

To compress configuration files, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# service compress-config	Specifies that the configuration file be compressed.
Step 2	Router(config)# end	Exits global configuration mode.
Step 3	Use FTP, rcp, or TFTP to copy the new configuration. If you try to load a configuration that is more than three times larger than the NVRAM size, the following error message is displayed: "[buffer overflow - file-size/buffer-size bytes]." or Router# configure terminal	Enters the new configuration.
Step 4	Router(config)# copy system:running-config nvram:startup-config	When you have finished changing the running-configuration, saves the new configuration.

Storing the Configuration in Flash Memory on Class A Flash File Systems

On Class A Flash file system routers, you can store the startup configuration in Flash memory by setting the CONFIG_FILE environment variable to a file in internal Flash memory or Flash memory in a PCMCIA slot.

To store the startup configuration in Flash memory, use the following commands beginning in privileged EXEC mode:

	Command	Purpose
Step 1	Router# copy nvram:startup-config flash-filesystem:filename	Copies the current startup configuration to the new location to create the configuration file.
Step 2	Router# configure terminal	Enters global configuration mode.
Step 3	Router(config)# boot config flash-filesystem:filename	Specifies that the startup configuration file be stored in Flash memory by setting the CONFIG_FILE variable.
Step 4	Router(config)# end	Exits global configuration mode.
Step 5	Use FTP, rcp, or TFTP to copy the new configuration. If you try to load a configuration that is more than three times larger than the NVRAM size, the following error message is displayed: "[buffer overflow - file-size/buffer-size bytes]." or Router# configure terminal	Enters the new configuration.
Step 6	Router# copy system:running-config nvram:startup-config	When you have finished changing the running-configuration, saves the new configuration.

Loading the Configuration Commands from the Network

You can also store large configurations on FTP, rcp, or TFTP servers and download them at system startup. To use a network server to store large configurations, use the following commands beginning in privileged EXEC mode:

	Command	Purpose
Step 1	Router# copy system:running-config {ftp: | rcp: | tftp:}	Saves the running configuration to an FTP, rcp, or TFTP server.
Step 2	Router# configure terminal	Enters global configuration mode.
Step 3	Router(config)# boot network {ftp:[[[//[username[:password]@]location]/director y]/filename] | rcp:[[[//[username@]location]/directory]/filename] |tftp:[[[//location]/directory]/filename]}	Specifies that the startup configuration file be loaded from the network server at startup.
Step 4	Router(config)# service config	Enables the router to download configuration files at system startup.
Step 5	Router(config)# end	Exits global configuration mode.
Step 6	Router# copy system:running-config nvram:startup-config	Saves the configuration.