Cisco IOS user interface is divided into different modes. Use ? to check list of commands available in that mode.
When we first login into the switch or router, we are in user mode also known as EXEC mode. This mode is identified with “>” symbol. It has limited commands. Only show or clear commands are available. We can use clear command to reset the interface counters. The second mode is the Privileged mode and it is identified with “#” symbol.
csr1000v-1#?
Exec commands:
<1-99> Session number to resume
access-profile Apply user-profile to interface
access-session Access-session options for eEdge
alps ALPS exec commands
app-hosting Application hosting
appnav IOS Wide Area Application Services
archive manage archive files
attach Connect to a module's console
audio-prompt load ivr prompt
authentication Authentication options for eEdge
auto Exec level Automation
beep Blocks Extensible Exchange Protocol commands
bfe For manual emergency modes setting
bulkstat Bulkstat exec commands
call Voice call
call-home Call-Home commands
cd Change current directory
clear Reset functions
clock Manage the system clock
cns CNS agents
configure Enter configuration mode
connect Open a terminal connection
controller-mode controller-mode service
copy Copy from one file to another
credential load the credential info from file system
crypto Encryption related commands.
cts Cisco Trusted Security Exec Commands
debug Debugging functions (see also 'undebug')
delete Delete a file
diagnostic Diagnostic commands
dir List files on a filesystem
disable Turn off privileged commands
disconnect Disconnect an existing network connection
dns DNS Protocol commands
do-exec Mode-independent "do-exec" prefix support
dot1x IEEE 802.1X Exec Commands
eap EAP Exec Commands
emadmin Extension Mobility Commands
enable Turn on privileged commands
erase Erase a filesystem
ethernet Ethernet parameters
To make changes to a device, we must go into global configuration mode. Use configuration terminal to move into global configuration mode. From global configuration mode, we can make changes to the running configuration, add an IP address to the interface, configure SSH or telnet.
csr1000v-1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
csr1000v-1(config)#
Interface configuration mode
csr1000v-1(config)#interface GigabitEthernet1
csr1000v-1(config-if)#
Line configuration mode
csr1000v-1(config)#line vty 0 4
csr1000v-1(config-line)#
Firewallfc 