Cisco IOS is divided into number of modes such as user EXEC mode, Privileged mode, global configuration mode, interface/subinterface mode and protocol specific mode.
Commands available to us depend on which mode we are currently in. We can use question mark ? to check list of commands available in that mode
connect Open a terminal connection
disable Turn off privileged commands
disconnect Disconnect an existing network connection
enable Turn on privileged commands
exit Exit from the EXEC
logout Exit from the EXEC
ping Send echo messages
resume Resume an active network connection
show Show running system information
telnet Open a telnet connection
terminal Set terminal line parameters
traceroute Trace route to destination
When we first login into Cisco device, we are in user mode also known as EXCE mode. Only limited set of commands are available in this mode. We can check number of commands available in this mode by typing ? . Some show commands and clear interface or counter are available in this mode. We cannot make any configuration changes in this mode.
Second mode is the Privileged mode. Use enable command followed by password to enter into privileged mode. Privileged mode is identified by # sign.
By default, no password is configured to move into privileged mode. Setting enable password will prompt password whenever we are moving from user mode to privileged mode.
Switch(config)#enable password cisco
In the above code, we have configured enable password. Switch will prompt for password whenever we are changing mode from user to privileged mode.
Commands available in privileged mode
– Restart router
– Erasing the configuration of a device
– Copy and save the configuration
Use configure terminal command to move into global configuration mode
In global configuration mode, we can make changes to configuration of a device.
Interface configuration allows us to set parameters for a interface,
Switch(config)#interface fastEthernet 0/1
cdp Global CDP configuration subcommands
channel-group Etherchannel/port bundling configuration
channel-protocol Select the channel protocol (LACP, PAgP)
description Interface specific description
duplex Configure duplex operation.
exit Exit from interface configuration mode
ip Interface Internet Protocol config commands
lldp LLDP interface subcommands
mdix Set Media Dependent Interface with Crossover
mls mls interface commands
no Negate a command or set its defaults
shutdown Shutdown the selected interface
spanning-tree Spanning Tree Subsystem
speed Configure speed operation.
storm-control storm configuration
switchport Set switching mode characteristics
tx-ring-limit Configure PA level transmit ring limit