Help, autocompletion, monitoring, shortcuts

Help#

The option that displays the available options for a command is ?

Router#show ?
  aaa                Show AAA values
  access-lists       List access lists
  arp                Arp table
  cdp                CDP information
  class-map          Show QoS Class Map
  clock              Display the system clock
  controllers        Interface controllers status
  crypto             Encryption module
  debugging          State of each debugging option
  dhcp               Dynamic Host Configuration Protocol status
  dot11              IEEE 802.11 show information
  file               Show filesystem information
  flash:             display information about flash: file system
  flow               Flow information
  frame-relay        Frame-Relay information
  history            Display the session command history
  hosts              IP domain-name, lookup style, nameservers, and host table
  interfaces         Interface status and configuration
  ip                 IP information
  ipv6               IPv6 information
  license            Show license information
  line               TTY line information
 --More--

Here the ? shows the possible commands with show.

The --More-- indicates that there are too many commands for the display window.
The Enter key scrolls line by line.
The Space key scrolls block by block.

Autocompletion#

Commands autocomplete with the tab key.
Here are some examples:

sh <tab> becomes show
int becomes interface

You can start typing the command and press TAB as soon as possible. There may be ambiguity. You need to continue typing to specify the command to the system. So it can complete it correctly.

Filtering results#

🫱 Adding | after a command allows you to filter its result:

interface GigabitEthernet0/0/0
interface GigabitEthernet0/0/1
interface GigabitEthernet0/0/2
interface Vlan1

Here include filters the result to include the word interface.

Abbreviated commands#

The Cisco CLI supports command abbreviations.
Here are some examples:

Abbreviation	Full command
conf t	configure terminal
sh ip int b	show interface brief
wr	Write memory
int g0/0	interface GigabitEthernet0/0

Error reporting#

The environment indicates where there is an error.
Incorrect syntax or wrong mode (do “command”).

Router#sh ip routte
                 ^
% Invalid input detected at '^' marker.

Keyboard shortcuts#

Sequence	Description
`CTRL` + `A`	Beginning of line
`CTRL` + `E`	End of line
`CTRL` + `P` or `↓`	Previous command
`CTRL` + `N` or `↑`	Next command
`CTRL` + `F` or `→`	Cursor right
`CTRL` + `B` or `←`	Cursor left
`CTRL` + `Z`	Return to privileged mode
`CTRL` + `C`	Interrupt
`CTRL` + `SHIFT` + `6` / `CTRL` + `SHIFT` + `^`	Forced interruption
`TAB`	Complete a command
`Backspace`	Erase a character to the left
`CTRL` + `R`	Redisplay the line
`CTRL` + `U`	Erase the line
`CTRL` + `W`	Erase a word
`ESC` + `b`	Move back a word
`ESC` + `f`	Move forward a word

Some tips#

The do command allows you to execute a privileged mode command in another mode.

Switch(config)#show run
                 ^
% Invalid input detected at '^' marker.

Switch(config)#do show run
Building configuration...

Disabling DNS lookups#

With DNS resolution (enabled by default), a mistyped command can be interpreted, in privileged mode, as an attempt to connect to a remote domain and block the console for some time:

Switch#showe
Translating "showe"...domain server (255.255.255.255)

To disable DNS resolution:

no ip domain-lookup

Disabling announcements#

Each time you change the state of an interface (up, down, etc…)
The device writes a message in the CLI, indicating what has changed. This can be annoying when typing commands. It is possible to disable these announcements:

%LINK-1-CHANGED: Interface FastEthernet0/1, changed state to up

no logging console

Renaming a device#

hostname MY_SWITCH

Setting an enable password#

To enter the “enable” mode of the device, it is possible and even recommended to set a password.

Switch(config)#enable secret MY_PASSWORD

With the secret option, the password is hashed.

Viewing the general configuration#

To display information about the global configuration (hostname, services, interfaces, spanning-tree, password, etc.), execute this command:

Switch#show running-config
Building configuration...

Current configuration : 1080 bytes
!
version 15.0
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
!
interface FastEthernet0/2
--More--

Viewing VLAN configuration#

To display information about VLAN configuration:

Switch#show vlan

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/4
                                                Fa0/5, Fa0/6, Fa0/7, Fa0/8
                                                Fa0/9, Fa0/10, Fa0/11, Fa0/12
                                                Fa0/13, Fa0/14, Fa0/15, Fa0/16
                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20
                                                Fa0/21, Fa0/22, Fa0/23, Fa0/24
                                                Gig0/1, Gig0/2
1002 fddi-default                     active
1003 token-ring-default               active
1004 fddinet-default                  active
1005 trnet-default                    active

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1    enet  100001     1500  -      -      -        -    -        0      0
1002 fddi  101002     1500  -      -      -        -    -        0      0
1003 tr    101003     1500  -      -      -        -    -        0      0
1004 fdnet 101004     1500  -      -      -        ieee -        0      0
1005 trnet 101005     1500  -      -      -        ibm  -        0      0
 --More--

NOTE
VLANs 1002, 1003, 1004, 1005 are reserved in the system for token ring. This system being obsolete, these VLANs are not used.

Here interfaces F0/1-24 and G0/1-2 belong to VLAN 1.

Removing/disabling an element#

The no suffix allows you to remove/disable/delete any previously written command or configuration.

no ip address 192.168.1.1 255.255.255.0

Removes the IP address assigned to the interface.

Router(config)#no router ospf

Disables the OSPF protocol (and its configuration) from the router.