Using ? Command
Networking - Cisco

Using the ? Command There will be time when you as a network administrator will not be able to remember the command that is needed, in that case use the ? command. The following is a list of all commands that can be used in the privileged mode at the router prompt. Router#? Exec commands:

access-enable    Create a temporary Access-List entry
access-template Create a temporary Access-List entry
bfe For manual emergency modes setting
clear Reset functions
clock Manage the system clock
configure Enter configuration mode
connect Open a terminal connection
copy Copy configuration or image data
debug Debugging functions (see also 'undebug')
disable Turn off privileged commands
disconnect Disconnect an existing network connection
enable Turn on privileged commands
erase Erase flash or configuration memory
exit Exit from the EXEC
help Description of the interactive help system
lock Lock the terminal
login Log in as a particular user
logout Exit from the EXEC
mrinfo Request neighbor and version information from a multicast
mstat Show statistics after multiple multicast traceroutes

–More– ######### #########

mtrace           Trace reverse multicast path from destination to source
name-connection Name an existing network connection
no Disable debugging functions
pad Open a X.29 PAD connection
ping Send echo messages
ppp Start IETF Point-to-Point Protocol (PPP)
reload Halt and perform a cold restart
resume Resume an active network connection
rlogin Open an rlogin connection
rsh Execute a remote command
send Send a message to other tty lines
setup Run the SETUP command facility
show Show running system information
slip Start Serial-line IP (SLIP)
start-chat Start a chat-script on a line
systat Display information about terminal lines
telnet Open a telnet connection
terminal Set terminal line parameters
test Test subsystems, memory, and interfaces
traceroute Trace route to destination
tunnel Open a tunnel connection
undebug Disable debugging functions (see also 'debug')
verify Verify checksum of a Flash file
where List active connections
write Write running configuration to memory, network, or terminal
x3 Set X.3 parameters on PAD

The ? command can also be used in the global configuration mode. Take a look at all the commands available to the user.

Router#config t Enter configuration commands, one per line. End with CNTL/Z. Router(config)#? Configure commands:

aaa                         Authentication, Authorization and Accounting.
access-list Add an access list entry
alias Create command alias
arp Set a static ARP entry
async-bootp Modify system bootp parameters
autonomous-system Specify local AS number to which we belong
banner Define a login banner
boot Modify system boot parameters
bridge Bridge Group.
buffers Adjust system buffer pool parameters
busy-message Display message when connection to host fails
cdp Global CDP configuration subcommands
chat-script Define a modem chat script
clock Configure time-of-day clock
config-register Define the configuration register
default Set a command to its defaults
default-value Default character-bits values
dialer-list Create a dialer list entry
dnsix-dmdp Provide DMDP service for DNSIX
dnsix-nat Provide DNSIX service for audit trails
downward-compatible-config Generate a configuration compatible with older

–More– ######### ######### software

enable                      Modify enable password parameters
end Exit from configure mode
exit Exit from configure mode
frame-relay global frame relay configuration commands
help Description of the interactive help system
hostname Set system's network name
interface Select an interface to configure
ip Global IP configuration subcommands
key Key management
line Configure a terminal line
logging Modify message logging facilities
login-string Define a host-specific login string
map-class Configure static map class
map-list Configure static map list
menu Define a user-interface menu
modemcap Modem Capabilities database
multilink PPP multilink global configuration
netbios NETBIOS access control filtering
no Negate a command or set its defaults
ntp Configure NTP
partition Partition device
printer Define an LPD printer

–More– ######### ######### priority-list Build a priority list

privilege                   Command privilege parameters
prompt Set system's prompt
queue-list Build a custom queue list
resume-string Define a host-specific resume string
rif Source-route RIF cache
rlogin Rlogin configuration commands
rmon Remote Monitoring
route-map Create route-map or enter route-map command mode
router Enable a routing process
scheduler Scheduler parameters
service Modify use of network based services
snmp-server Modify SNMP parameters
state-machine Define a TCP dispatch state machine
tacacs-server Modify TACACS query parameters
terminal-queue Terminal queue commands
tftp-server Provide TFTP service for netload requests
username Establish User Name Authentication
x25 X.25 Level 3

Interface configuration is the most important part of a router configuration, without an interface the router cannot have any communication with any other devices. This command shows which Interfaces are available on this Cisco 2500 router.


Router(config)#interface ?

Async             Async interface
BVI Bridge-Group Virtual Interface
Dialer Dialer interface
Ethernet IEEE 802.3
Group-Async Async Group interface
Lex Lex interface
Loopback Loopback interface
Null Null interface
Serial Serial
Tunnel Tunnel interface
Virtual-Template Virtual Template interface

In this example I selected the ethernet interface, but remember to select which interface number you want to configure. If you don’t know which ones are available, use the ? command.

Router(config)#int ethernet0 Router(config-if)exit

Here is an example of the line command. Notice when I use the ? command which options are available. The bottom three are the ones that you will use the most.

Router(config)#line ?

<0-6>    First Line number
aux Auxiliary line
console Primary terminal line
vty Virtual terminal

Router(config)#line console 0 Router(config-line)#^Z Now here is an fun command. To set the time on a router use the following commands. Notice how I use the ? command to figure out what I need to do next.

Router#clock ?

set  Set the time and date

Router#clock set ?

hh:mm:ss  Current Time

Router#clock set 01:07:00# ?

<1-31>  Day of the month
MONTH Month of the year

Router#clock set 01:07:00 17 august ?

<1993-2035>  Year