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How To Save Configuration in Cisco Router And Erase Cisco Router Configuration– Cisco certifications labs using Cisco packet tracer

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How to Write,Display and Erase Configuration in a Cisco Router

Cisco configuration

In this tutorial you will learn how to save a configuration in cisco router, how to erase config on cisco router and Cisco commands for how to show cisco router running config and startup configuration. Cisco routers starts executing startup configurations, any changes made to the router’s configuration while it is running is erased on each restart of a router, if you do want to retain any changes made to the router configurations after a restart then you must know the cisco commands for saving running configuration to startup configuration. Commands for writing and displaying router running configurations or startup configuration can be executed in Privileged Exec mode. So for displaying, saving or erasing Cisco router configuration you need to be at the Privileged Exec mode. For more about Cisco router modes click here.

At Privileged mode (UpaaeRouter1 being the host name) the prompt will look like this UpaaeRouter1# .

Cisco Show Commands for displaying running configuration and startup configuration:

UpaaeRouter1# show running-config     // executing this command will display the router runningconfiguration. UpaaeRouter1# show startup-config   // executing this command displays/show startup configuration pf cisco router.

Cisco commands To save configurations in Cisco Router:

Save running configuration to startup configuration

UpaaeRouter1# copy running-config  startup-config    // this command will save the configuration changes you have made (running-configuration) to startup-configuration in the NVRAM.

Save startup configuration to running configuration

UpaaeRouter1# copy startup-config running-config   // this command will write the startup configuration to the running configuration.

How To Erase Configuration on Cisco Router:

If you want to clear the configuration of your cisco router follow these steps:

  1. Log on to your router.
  2. Enter the privileged EXEC by typing enable command.
  3. At privileged EXEC mode type write erase, which will erase the NVRAM file system and removes all files.
  4. Confirm that you want to erase all files at prompt.
  5. After the complete execution of “step 4” enter reload, and type no when prompted whether to save the configuration.
UpaaeRouter1# write erase UpaaeRouter1# reload    // these two commands will erase both running and startup configurations.
Recommended Resources for CCNA Exam:

Following are the resources which every Cisco Networking student should be equipped with, these will not only guarantee passing Cisco Exams, but will help you understand every pitfall and minor details of Cisco networking.

If you do have any questions in mind, please ask in comments section.


How to Manage and Save Running Config on Cisco Devices

Cisco IOS

The Cisco device stack uses the Internetwork operating system (IOS), which controls the device’s performance and behavior. The Cisco IOS defines an interface called the Command Line Interface (CLI), which enables administrators to enter commands into a terminal emulation program. The CLI can be accessed through three methods: the console, Telnet and Secure Shell (SSH).

Cisco Modes

Users can be logged in to a Cisco device using the following modes:

  • Exec mode (user mode) — Allows the user to look around but not change anything. Accessing the CLI by any of the three methods logs the user into Exec
  • Enable mode (privileged mode or privileged exec mode) — Allows the user to execute privileged commands, such as the reload command, which tells the switch to reboot the Cisco IOS. To enter this mode, the user runs the enable command mode.
  • Global configurationmode — Allows users to enter nondisruptive commands and display some information. Unlike exec and enable mode, configuration mode accepts configuration commands — commands that tell the switch the details of what to do and how to do it. Commands entered in configuration mode update the active configuration file, but the actual changes in configuration take place only after the device reboots. To enter configuration mode, a user executes the configure terminal (conf t) command.

Configuration mode contains several sub-modes. One is interface configuration mode, which can be entered by running the interface FastEthernet 0/1 (int fa0/1) configuration command.

Basic CLI Commands


The show command is one of the most helpful commands because you can find the status of almost every feature of the Cisco IOS. It reads the current configuration from the Cisco device’s RAM and lists the requested settings in the CLI. For example, the show version command displays information about the Cisco IOS version currently loaded on a device.


Like the show command, debug reveals information about the device’s settings. However, instead of just listing the current status, the debug command asks the device to continue monitoring different processes in it and send messages to the user when different events occur, showing the status of settings over time. As a result, the debug command takes more CPU cycles, but it lets you monitor what is happening in a switch in real time. In short, show is for reporting and debug is for monitoring.


The hostname command assigns a network name to the Cisco device.


Use the ? command to get answers to your questions about other commands, such as their syntax and description.

Where Configuration Files are Stored

A Cisco device needs to use the configuration file to do its work. Cisco devices have random-access memory (RAM) to store data from the configuration file while Cisco IOS is using it, but the RAM loses its contents when the device loses power. In order to load all configuration data back after the device loses power, Cisco use several types of more permanent memory. The following list explains the four main types of memory found in Cisco switches or Cisco routers, as well as the most common use of each type:

  • RAM — RAM is used by a Cisco device for working storage. The running configuration file is stored
  • ROM — Read-only memory (ROM) stores a bootstrap program that is loaded when the switch first powers on. This program finds the full Cisco IOS image and loads it into RAM.
  • Flash memory — This memory can be either inside the device or on a removable memory card. Flash memory stores fully functional Cisco IOS images and is the default location where the switch gets its Cisco IOS at boot time. Flash memory also can be used to store other files, including backup copies of configuration files.
  • NVRAM — Nonvolatile RAM (NVRAM) stores the initial or startup configuration file that is used when the Cisco device is powered on or reloaded.

Copying, Erasing and Saving Running Config on Cisco Devices

To change the configuration of a Cisco device, you need to enter configure terminal mode and then use one or more of the following commands.

Rename a device

Use the command hostname newnameto change the name of the device to the string you specify.

Save running config on Cisco device

Use the command copy running-config startup-config (copy run start) to overwrite the current startup config file with what is currently in the running configuration file.

Copy files

The copy command can be used to copy files on a Cisco device, such as a configuration file or a new version of the Cisco IOS. Files can be copied between RAM, NVRAM and a TFTP server. The syntax for the copy commands is as follows:

copy {tftp | running-config | startup-config} {tftp | running-config | startup-config}

The first set of parameters in braces is the “from” location; the next set is the “to” location. When a file is copied into NVRAM or a TFTP server, the copy command always overwrites the existing destination file with the new file. However, when the copy command copies a configuration file into the running config file in RAM, the configuration file in RAM is not replaced; it is merged instead.

Erase the contents of NVRAM

You can use three different commands to erase NVRAM: write erase, erase startup-config and erase nvram. All of them erase the contents of the NVRAM configuration file, so if the device is then reloaded, there is no initial configuration and you have to begin initial device configuration.

Note that Cisco IOS does not have a command that erases the contents of the running configuration file. To clear out the running config file, simply erase the startup config file and then reload the device.

Securing Login to Cisco Devices

Cisco devices authenticate users as they log in, but the default configuration uses only simple password security and the enablepassword command defines the password for the current login. You can help protect enable mode by using the enable secret command instead. The older enable password command stores the password as clear text in the running configuration, and the only way to encrypt it is to use the weak service password-encryption command. The newer enable secret command automatically encodes the password using a Message Digest 5 (MD5) hash.

Initial Configuration of Cisco Devices

Cisco switches leave the factory with the following default settings:

  • All interfaces are enabled.
  • Auto-negotiation is enabled for ports that can use it (duplex auto and speed auto).
  • All interfaces are a part of VLAN 1.

All you have to do with a new Cisco switch is make all the physical connections — Ethernet cables and a power cord — and it starts working.

To configure the switch:

  1. Enter VLAN 1 configuration mode using the interface vlan 1 global configuration command.
  2. Assign an IP address and mask using the ip addressip-address mask
  3. Enable the VLAN 1 interface using the no shutdown
  4. Add the default gateway with ip default-gateway
  5. Add the DNS server using the ip name-server command to resolve names into IP addresses.

After the initial configuration, you can look at the IP address and mask information using the show interface vlan x command, which shows detailed status information about the VLAN interface. If you use DHCP, use the show dhcp lease command to see the leased IP address.

You can see some of the details of the interface configuration using the show running-config command or the handy show interfaces status command, which lists each interface on a single line that shows the first part of the interface description and the speed and duplex settings.

The show port-security interface command lists the configuration settings for port security on an interface, along with several important facts about the current operation of port security, including information about any security violations. The switch can be configured to take one of three actions when a violation occurs using the following command:  switchport port-security violation {protect | restrict | shutdown}. All three options cause the switch to discard the offending frame, but some of the options make the switch take additional actions, such as sending syslog messages to the console, sending SNMP trap messages to the network management station, or disabling the interface.


As you can see, it is very easy to save the running config, copy it to a tftp server and perform the initial configuration for a Cisco device. Before changing the running config, be sure to make a backup.

Jeff Melnick

Jeff is a former Director of Global Solutions Engineering at Netwrix. He is a long-time Netwrix blogger, speaker, and presenter. In the Netwrix blog, Jeff shares lifehacks, tips and tricks that can dramatically improve your system administration experience.

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Table Of Contents

IOS and Configuration Basics

Cisco IOS Modes of Operation

Getting Context-Sensitive Help

Saving Configuration Changes

Manually Configuring RPM

Verifying Network Connectivity

IOS and Configuration Basics

This appendix contains basic information about the Cisco Internet Operating System (IOS) software and includes the following sections:

Cisco IOS Modes of Operation

Getting Context-Sensitive Help

Saving Configuration Changes

Cisco IOS Modes of Operation

Cisco IOS software provides access to several different command modes. Each command mode provides a different group of related commands.

For security purposes, Cisco IOS software provides two levels of access to commands: user and privileged. The unprivileged user mode is called user EXEC mode. The privileged mode is called privileged EXEC mode and requires a password. The commands available in user EXEC mode are a subset of the commands available in privileged EXEC mode.

Table C-1 describes some of the most commonly used modes, how to enter the modes, and the resulting prompts. The prompt helps you identify which mode you are in and, therefore, which commands are available to you.

Mode of Operation


How to Enter the Mode



User EXEC commands allow you to connect to remote devices, change terminal settings on a temporary basis, perform basic tests, and list system information. The EXEC commands available at the user level are a subset of those available at the privileged level.

Log in.


Privileged EXEC

Privileged EXEC commands set operating parameters. The privileged command set includes those commands contained in user EXEC mode, and also the configure command through which you can access the remaining command modes. Privileged EXEC mode also includes high-level testing commands, such as debug.

Enter the enable EXEC command from user EXEC mode.


Global configuration

Global configuration commands apply to features that affect the system as a whole.

Enter the configure privileged EXECcommand from global configuration mode.


Interface configuration

Interface configuration commands modify the operation of an interface such as an Ethernet or serial port. Many features are enabled on a per-interface basis. Interface configuration commands always follow an interface global configuration command, which defines the interface type.

Enter the interface type numbercommand from global configuration mode. For example, enter the interface int switch 9/1 command to configure the ATM interface.


ROM monitor

ROM monitor commands are used to perform low-level diagnostics. You can also use the ROM monitor commands to recover from a system failure and stop the boot process in a specific operating environment.1

Enter the reload EXEC command from privileged EXEC mode. Click BREAK during the first 60 seconds while the system is booting.


Almost every configuration command also has a no form. In general, use the no form to disable a feature or function. Use the command without the keyword no to reenable a disabled feature or to enable a feature that is disabled by default. For example, IP routing is enabled by default. To disable IP routing, enter the no ip routing command and enter ip routing to reenable it. The Cisco IOS software command reference publication provides the complete syntax for the configuration commands and describes what the no form of a command does.

Getting Context-Sensitive Help

In any command mode, you can list the available commands by entering a question mark (?).

To obtain a list of commands that begin with a particular character sequence, type in those characters followed immediately by the question mark (?). Do not include a space. This form of help is called word help because it completes a word for you.

To list keywords or arguments, enter a question mark in place of a keyword or argument. Include a space before the question mark. This form of help is called command syntax help, because it reminds you which keywords or arguments are applicable, based on the commands, keywords, and arguments you have already entered.

memory Configure from NV memory
network Configure from a TFTP network host
terminal Configure from the terminal

You can also abbreviate commands and keywords by entering just enough characters to make the command unique from other commands. For example, you can abbreviate the show command to sh.

Saving Configuration Changes

Whenever you make changes to the RPM configuration, you must save the changes to memory so they will not be lost if the system is rebooted. There are two types of configuration files: the running (current operating) configuration and the startup configuration. The running configuration is stored in RAM; the startup configuration is stored in NVRAM.

To display the current running configuration, enter the show running-config command. Enter the copy running-config startup-config command to save the current running configuration to the startup configuration file in NVRAM.

MGX8850-RPM# copy running-config startup-config

To display the startup configuration, enter the show startup-config command. Enter the copy startup-config running-config command to write the startup configuration to the running configuration.

MGX8850-RPM# copy startup-config running-config

To erase both configuration files (and start over), enter the write erase and reload commands:

Warning This command sequence will erase the entire RPM configuration in RAM and NVRAM and reload the RPM.

Manually Configuring RPM

You can configure the RPM manually if you prefer not to use AutoInstall or the prompt-driven System Configuration Dialog.

Take the following steps to configure the RPM manually:

Step 1 Connect a console terminal to the RPM.

Follow the instructions described in "Installing the MGX RPM," in the section "Connecting a Console Terminal or PC to the RPM Console Port," and then power on the RPM.

Step 2 When you are prompted to enter the initial dialog, enter no to go into the normal operating mode of the RPM:

Would you like to enter the initial dialog? [yes]: no

Step 3 After a few seconds you will see the user EXEC prompt (Router>).

By default, the host name is Router, but the prompt will match the current host name. In the following examples, the host name is MGX8850-RPM. Enter the enable command to enter enable mode. You can make configuration changes only in enable mode:

The prompt will change to the privileged EXEC (enable) prompt, MGX8850-RPM#.

Step 4 Enter the configure terminal command at the enable prompt to enter configuration mode:

MGX8850-RPM# config terminal

You can now enter any changes you want to the configuration. You will probably want to perform the following tasks:

1. Assign a host name for the RPM using the hostname command.

2. Enter an enable secret using the enable secret command.

3. Enter an enable password using the enable password command.

4. Assign addresses to the interfaces using the protocoladdress command.

5. Specify which protocols to support on the interfaces.

Refer to the Cisco IOS configuration and command reference publications for more information about the commands you can use to configure the RPM. You can also refer to the MGX 8850 Wide Area Switch Command Reference and MGX 8850 Wide Area Switch Installation and Configuration documentsfor information about the commands you can use to configure the RPM.

Step 5 When you finish configuring the RPM, enter the exit command until you return to the privileged EXEC prompt (MGX8850-RPM#).

Step 6 To save the configuration changes to NVRAM, enter the copy run start command at the privileged EXEC prompt:

MGX8850-RPM# copy run start

The RPM is now configured and will boot with the configuration you entered.

This concludes the initial RPM configuration.

Verifying Network Connectivity

When you have installed and configured the RPM, you can use the following commands in user EXEC mode to verify network connectivity:

ping—Sends a special datagram to the destination device, then waits for a reply datagram from that device
See "Verifying Network Connectivity" of Chapter 5 in this manual for a detailed ping procedure.

telnet—Logs in to a remote node

traceroute—Discovers the routes that packets take when traveling from one RPM to another

If there is a problem with network connectivity, see "Maintaining the MGX RPM" in the section "Reading Front Panel LEDs," and check the cable connections. If there is still a problem, check the RPM configuration. Contact customer service for further assistance.

How to Back Up and Restore Cisco Router Configs in the Command Line: Cisco Router Training 101

Diffrence between "wr" and "copy running config to startup config"

They essentially achieve the same things by saving the running configuration to the memory so that after a reload it retains the same configuration. Write memory is the "ancient" way, and copy running-config startup-config is the "newer way". Some newer platforms do not accept write memory, the Nexus platforms for instance. The workaround is to create an alias using in global configuration mode.

The "copy run start" command is just a variation of the "copy" command. The copy command can be used to copy any files in or out of the flash etc. - as opposed to just saving the configuration. Just remember though, if you are in the wrong configuration register "wr" will lose your configuration after a reload/when you change the configuration register whereas "copy run start" will just copy the contents of the running configuration to the start-up configuration.

When doing CCNA exams, the command "write" is not allowed. It has to be the official "copy running-config startup-config".

The reason why the "wr" or "write" command is very popular are:

  1. A minimum of two characters to save a config;

  2. It is easy to confuse "copy start run" with "copy run start".


answered Aug 5 '18 at 12:39


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Cisco CLI for Beginners - Network Fundamentals Part 10

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