We’ve already learned that IOS has three main command modes: the user exec, privileged exec, and the global configuration modes. Each of these modes serves a different purpose and has its own set of commands. In this lesson we will describe each of this modes in more detail.
User EXEC mode commands
Initially, a user logs into the User Exec mode. This is the mode with the least number of commands. You can get a list of all available commands by typing the character ?.
Router>?Exec commands:<1-99> Session number to resumeconnect Open a terminal connectiondisable Turn off privileged commandsdisconnect Disconnect an existing network connectionenable Turn on privileged commandsexit Exit from the EXEClogout Exit from the EXECping Send echo messagesresume Resume an active network connectionshow Show running system informationssh Open a secure shell client connectiontelnet Open a telnet connectionterminal Set terminal line parameterstraceroute Trace route to destination
As you can see, most of the commands available are used to show statistics and perform some basic troubleshooting. The prompt on the left side of the screen always displays the device hostname (R1 in this case), followed by the character >.
All commands can be abbreviated to their first letters of the command name. For example, you can abbreviate ping by typing pin, because no other command in the User EXEC mode IOS mode begins with these letters.
Privileged EXEC mode commands
This IOS mode is also called enable mode because you must enter the enable command from a user EXEC mode if you want to access this mode. You can use more commands in the privileged EXEC mode than you were able to use in the user EXEC mode. You can save a device configuration or reload a device in this mode. You can also enter a third mode, the configuration mode. The access to the privileged EXEC mode is usually protected with a password.
The prompt for this mode shows # after the device hostname.
Router>enRouter#?Exec commands:<1-99> Session number to resumeauto Exec level Automationclear Reset functionsclock Manage the system clockconfigure Enter configuration modeconnect Open a terminal connectioncopy Copy from one file to anotherdebug Debugging functions (see also 'undebug')delete Delete a filedir List files on a filesystemdisable Turn off privileged commandsdisconnect Disconnect an existing network connectionenable Turn on privileged commandserase Erase a filesystemexit Exit from the EXEClogout Exit from the EXECmkdir Create new directorymore Display the contents of a fileno Disable debugging informationsping Send echo messagesreload Halt and perform a cold restartresume Resume an active network connectionrmdir Remove existing directorysend Send a message to other tty linessetup Run the SETUP command facilityshow Show running system informationssh Open a secure shell client connectiontelnet Open a telnet connectionterminal Set terminal line parameterstraceroute Trace route to destinationundebug Disable debugging functions (see also 'debug')vlan Configure VLAN parameterswrite Write running configuration to memory, network, or terminal
Global configuration mode commands
To change a device configuration, you need to enter the global configuration mode. This mode can be accessed by typing configure terminal (or conf t, the abbreviated version of the command) from the enable mode. The prompt for this mode is hostname(config).
Global configuration mode commands are used to configure a device. You can set a hostname, configure authentication, set an IP address for an interface, etc. From this mode you can also access submodes, for example the interface mode, from where you can configure interface options.
You can get back to a privileged EXEC mode by typing the end command. You can also type CTRL + C to exit the configuration mode.
Router#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)#?Configure commands:aaa Authentication, Authorization and Accounting.access-list Add an access list entrybanner Define a login bannerbba-group Configure BBA Groupboot Modify system boot parameterscdp Global CDP configuration subcommandsclass-map Configure Class Mapclock Configure time-of-day clockconfig-register Define the configuration registercrypto Encryption moduledefault Set a command to its defaultsdo To run exec commands in config modedot11 IEEE 802.11 config commandsenable Modify enable password parametersend Exit from configure modeexit Exit from configure modeflow Global Flow configuration subcommandshostname Set system's network nameinterface Select an interface to configureip Global IP configuration subcommandsipv6 Global IPv6 configuration commandskey Key managementlicense Configure license featuresline Configure a terminal linelldp Global LLDP configuration subcommandslogging Modify message logging facilitieslogin Enable secure login checkingmac-address-table Configure the MAC address tableno Negate a command or set its defaultsntp Configure NTPparameter-map parameter mapparser Configure parserpolicy-map Configure QoS Policy Mapport-channel EtherChannel configurationpriority-list Build a priority listprivilege Command privilege parametersqueue-list Build a custom queue listrouter Enable a routing processsecure Secure image and configuration archival commandssecurity Infra Security CLIsservice Modify use of network based servicessnmp-server Modify SNMP engine parametersspanning-tree Spanning Tree Subsystemtacacs-server Modify TACACS query parametersusername Establish User Name Authenticationvpdn Virtual Private Dialup Networkvpdn-group VPDN group configurationzone FW with zoningzone-pair Zone pair command
Submode commands
A global configuration mode contains many submodes. For example, if you want to configure an interface you have to enter that interface configuration mode. Each submode contains only commands that pertain to the resource that is being configured.
To enter the interface configuration mode you need to specify which interface you would like to configure. This is done by using the interface INTERFACE_TYPE/INTERFACE_NUMBER global configuration command, where INTERFACE_TYPE represents the type of an interface (Ethernet, FastEthernet, Serial…) and INTERFACE_NUMBER represents the interface number, since CIsco devices usually have more than one physical interface. Once inside the interface configuration mode, you can get a list of available commands by typing the “?” character. Each submode has its own prompt. Notice how the command prompt was changed to Router(config-if) after I’ve entered the interface submode:
Router(config)#interface GigabitEthernet 0/1Router(config-if)#?arp Set arp type (arpa, probe, snap) or timeoutbandwidth Set bandwidth informational parametercdp CDP interface subcommandschannel-group Add this interface to an Etherchannel groupcrypto Encryption/Decryption commandscustom-queue-list Assign a custom queue list to an interfacedelay Specify interface throughput delaydescription Interface specific descriptionduplex Configure duplex operation.exit Exit from interface configuration modefair-queue Enable Fair Queuing on an Interfacehold-queue Set hold queue depthip Interface Internet Protocol config commandsipv6 IPv6 interface subcommandslldp LLDP interface subcommandsmac-address Manually set interface MAC addressmtu Set the interface Maximum Transmission Unit (MTU)no Negate a command or set its defaultspppoe pppoe interface subcommandspppoe-client pppoe clientpriority-group Assign a priority group to an interfaceservice-policy Configure QoS Service Policyshutdown Shutdown the selected interfacespeed Configure speed operation.standby HSRP interface configuration commandstx-ring-limit Configure PA level transmit ring limit
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