What is the basic operation of Cisco devices

Source: Internet
Author: User
Tags reset lost password

Operation mode

Cisco iOS offers several different command-mode modes, each of which provides a set of related commands, different operational permissions, and operational functions.

Commands and functions in iOS environment:

User mode

prompt User Rights How to enter
Normal User mode
Normal user command
Automatic access to the power
Privileged User mode
Management of the system
VLAN configuration mode
Router (VLAN) #
VLAN and VTP Management
Router#vlan data
Configuration mode
Router (config) #
System for Configuration
Router#config T

Configuration of common interfaces

Configuring virtual interfaces

Router (config) #interface loopback0

Configuring the Serial0 Interface

Router (config-if) #interface S0

Configuring the Ethernet0 Interface

Router (config-if) #interface E0

Configuring the Fa0 Interface

Router (config-if) #interface Fa0

Configuring the Atm0 Interface

Router (config-if) #interface Atm0

Configuring Port IP Addresses

Router (config-if) #ip address Port IP Mask


Routing configuration Command 1. Static routing

Router (config) #ip Route IP address of the next hop router in the destination network address mask

2. Default route

Router (config) #ip Route The IP address of the next hop router

Quarantine commands for basic routers

Show version

Show processes

Show Protocols

Show Mem

Show IP route

Show Startup-config

Show Running-config

Show Flash

Show interfaces

Check the connectivity of the network

Ping Host name/IP address

Trace Host name/IP address

Traffic feature Check command

You can often use this command to discover unusual traffic to discover virus machines and IP addresses.

Show ip Cahce Flow

Security maintenance of system maintenance system

In addition to the network security system maintenance, network system equipment itself security maintenance is also very important.

Set Remote login Password

This password is used for network administrator remote Telnet logon into user mode, and remote administrators cannot log on if this password is not set.

R2621>enable!! Enter Privileged mode

R2621#configure Terminal!! Enter Global configuration mode

R2621 (config) #line vty 0 4!! Start configuring Telnet

R2621 (config-line) #password Cisco!! Set the password for Telnet

R2621 (config-line) #login!! Enable this password

Set Local

Console port Password This password is used by the local network administrator to enter user mode from the console port, and if the password is not set, the user can enter user mode directly.

R2621>enable!! Enter Privileged mode

R2621#configure Terminal!! Enter Global configuration mode

R2621 (config) #line con 0!! Start Configuring console

R2621 (config-line) #password Cisco!! Set Password for console

R2621 (config-line) #login!! Enable this password

Set the password for privileged mode the

The password is used for network administrators to enter privileged mode from normal user mode.

R2621>enable!! Enter Privileged mode

R2621#configure Terminal!! Enter Global configuration mode

R2621 (config) #enable secret Cisco!! will enable password The password is stored after encryption

Recover lost Password

Cisco router is one of the widely used computer network communication devices. In daily operation, the router plays an important role in the whole system, and it is unavoidable to operate it frequently. For example: Modify router configuration files, diagnose network failures, and so on. Once the password is forgotten, it can cause great trouble to the job, at this point, how to recover the password becomes particularly important.


Note You cannot recover the encrypted password because the password is not visible. You must remove the original configuration and set a new password.


Follow the process below to recover the password (enable password):

Step 1 connects the ASCII terminal or PC running the terminal emulator to the console port on the front panel of the router.

Step 2 to reboot the router. If you see the following prompts, enter N:

Would to enter the initial dialog? [Yes]: n

You then enter the normal operating state of the router.

Step 3 seconds after you see the user command prompt, EXEC prompt (router>). Enter the show version command to display the current configuration register value and record its configuration.

Step 4 If the interrupt function is turned on, type the break key to display the ROM monitor prompt (Rommon >). Go directly to step 6.

Step 5 I if the interrupt function is not turned on, or you cannot determine if it is turned on, turn off the router, wait 5 seconds, and then restart the router. In the first 5 seconds of the router startup, type the break key. The terminal displays the ROM monitor prompt (Rommon >).

Step 6 enters Confreg at the ROM monitor prompt, which allows you to configure register values.

Rommon> Confreg

Step 7 Enter Y in the following prompt state:

Do your wish to change the configuration? y/n [n]: Y

Step 8 always enter n for all prompts until you encounter the following prompts, and then enter Y:

Enable "Ignore system config Info"? [y/n] N:y

Step 9 always enter n for all prompts until you encounter the following prompts, and then enter Y:

Change the boot characteristics? [y/n] [n]: Y

Step 10 at the prompt below, type 2 and press ENTER. Configuration status will be displayed.

Enter to Boot:2

Step 11 Enter N at the following prompt:

Do your wish to change the configuration? y/n [n]: N

Step 12 enters reset at the ROM monitor prompt and the router resets.

rommon> Reset

Step 13 Enter n at the following prompt:

Would to enter the initial dialog? [Yes]: no

Step 14 Enter enable to enter privileged Command mode privileged EXEC mode:

Router> Enable



Configuration can be changed only in enable mode. The prompt becomes privileged command mode prompt privileged EXEC prompt (router#):

Step 15 Enter the show Startup-config command to display the enable password in the configuration file:

router# Show Startup-config

Step 16 Enter the Configure Terminal command to enter configuration mode:

router# Configure terminal

Step 17 Enter the Configure register command to restore the original register value.

Step 18 Press Ctrl-z to exit configuration mode.

Step 19 Reboot the router and enter the password for recovery.


Version upgrades regularly upgrade iOS is important for device security, and here's a quick overview of how to upgrade iOS.

iOS version upgrade common commands

Router#dir all! Displays the version number of iOS on Flash

Router#copy Flash TFTP! Backup iOS system files to TFTP Server

Router#copy TFTP flash! Update system files on flash from TFTP server

Router#delete: File name! delete system files on Flash

Router#reload, Reboot!

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