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Cisco IOS Commands

This is the master list of some of the many Cisco IOS Commands that go with the CCNA track. This list also talks about what each command does in brief detail. You may also find that some commands may or may not be used for a CCNA level but offer some important information. If you don’t know what a command does or understand it, I would look at Cisco documentation.

Since this is a pretty big list of commands you can see the links to move to the different sections within this page. Enjoy!
Privileged Mode
Set a password for console access
Set a Password for virtual terminal (telnet) access
Set a password for auxiliary (modem) access
Setting up the Router
General Commands
Processes and Statistics
CDP Commands
Miscellaneous Commands


Privileged Mode:

Router>enable

This command “enable”will get you in privileged mode in the router or switch.

Router#disable
Router>

This command “disable” will put you back to the user mode in the router or switch.

Router(config)#enable password knowing

This will put a unencrypted password on the privileged mode (in this example the password would be “knowing”)

Router(config)#enable secret knowing

This command will put an encrypted password on the privileged mode (in this example the password would be “knowing”)


Set a password for console access:

Router(config)#line console 0
Router(config-line)#login
% Login disabled on line 0, until 'password' is set
Router(config-line)#password allknowing

This sets the password as “allknowing” when accessed by the consolde line in a router or switch.


Set a Password for virtual terminal (telnet) access:

Router(config)#line vty 0 4
Router(config-line)#login
% Login disabled on line 66, until 'password' is set
% Login disabled on line 67, until 'password' is set
% Login disabled on line 68, until 'password' is set
% Login disabled on line 69, until 'password' is set
% Login disabled on line 70, until 'password' is set
Router(config-line)#password knowingall

Remember you must have a password on telnet to access the router or switch with a telnet session otherwise the router or switch will close the session immediately. This sets the password as “knowingall”


Set a password for auxiliary (modem) access:

Router(config)#line aux 0
Router(config-line)#login
Router(config-line)#password all

This sets the password as “all” when accessed via the auxiliary port.


Setting up the Router:

Router#show running-config
Building configuration...
<output omitted="">

This command “show running-config” shows the details of the running configuration file in RAM.

Router#show startup-config

This command “show startup-config” shows the details of the startup configuration file in NVRAM (If there is one saved)

Router#setup

--- System Configuration Dialog ---

Continue with configuration dialog? [yes/no]: 

This command will start the automatic setup process, (The same as when you first boot the router)

Router#configure terminal 

This command “configure terminal” is used to execute configuration commands from the terminal.

Router#configure memory

This command “configure memory” is used to execute configuration commands stored in NVRAM.

Router#configure network

This command “configure network” is used to retrieve configuration from a TFTP server.

Router#copy startup-config running-config

This command “copy startup-config running-config” will copy the startup configuration file to the running configuration file.

Router#copy running-config startup-config

This command “copy running-config startup-config” will copy the running configuration fiel to the startup configuration file.

Router(config)#boot system flash

This command “boot system flash” will tell the router which IOS file in flash to boot from.

Router(config)#boot system tftp

This command “boot system tftp” will tell the router which IOS file on the TFTP server to boot from.

Router(config)#boot system rom

This command “boot system rom” will tell the router to boot from ROM at next boot.

Router#copy flash tftp:

This command “copy flash tftp:” will copy the flash to a TFTP server.

Router#copy tftp flash:

This command “copy tftp flash:” will restore flash from a TFTP server.

Router#copy running-config tftp

This command “copy running-config tftp” will copy the current running configuration file to a TFTP server.

Router#copy tftp running-config

This command “copy tftp running-config” will restore the running configuration file from a TFTP server.


General Commands:

Router(config-if)#no shutdown

The command “no shutdown” will enable the interfaces on the router

Router#reload

The command “reload” will restart the router.

Router#show version

The command “show version” displays the Cisco IOS version, uptime, of the router, how the router started, where the system was loaded from, along with the configuration register.

Router#show clock

The command “show clock” will display the date and time.

Router#show history

The command “show history” will display the past commands that you entered earlier.

Router#show debug

This command “show debug” will show all debugging that is currently enabled.

Router#no debug all

The command “no debug all” turns off all possible debugging.

Router#show users

This command “show users” will show users that are connected to the router

Router#show protocols

This command “show protocols” displays which protocols are configured.

Router(config)#banner motd #
Enter TEXT message.End with the character '#'.

The command “banner motd” will set or change the banner. (The “#” symbol at the end is a custom symbol the user uses)

Router(config)#hostname R1

The command “hostname” is used to configure the hostname of the router (for this example the router’s hostname is “R1″)

Router#clear counters

The command “clear counters” will clear the connection counters.


Processes and Statistics

Router#show processes

The command “show processes” shows the active processes running on the router.

Router#show processes cpu

The command “show processes cpu” shows CPU statistics.

Router#show memory

The command “show memory” shows memory statistics.

Router#show flash

The command “show flash” describes the flash memory and displays the size of the files and the amount of free flash memory.

Router#show buffers

The command “show buffers” displays the stats for the router buffer pools.

Router#show stacks

The command “show stacks” shows the reason for last reboot, and monitors the stack use of the processes and interrupts routines.


CDP Commands- Cisco Discovery Protocol uses a layer 2 multicast over SNAP capable links to send data.

Router#show cdp neighbors

Shows directly connected neighbors.

Router#show cdp neighbors

Shows and displays more information about the neighbor device.

Router#show cdp interface

Shows which interfaces are running CDP.
(Example Output)

Router#show cdp interface fastEthernet 0/1
Vlan1 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/0 is up, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/1 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds

Shows CDP information on a specific interface.
(Example Output)

FastEthernet0/1 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds

 

Router#show cdp entry ?
* all CDP neighbor entries
WORD Name of CDP neighbor entry

Shows CDP neighbor detail based on the name of that device and or all CDP entries.

Router(config)#cdp timer 160

Change how often CDP information is sent. (updates) (This example is 160 seconds this can be any number the default is 60)

Router(config)#cdp holdtime 240

Change how long to wait before removing CDP information. (neighbor) (This example is 240 seconds this can be any number the default is 180)

Router(config-if)#no cdp enable

Turns off CDP on a specific interface.

Router(config-if)#cdp enable

Turns on CDP on a specific interface.

Router(config)#cdp run

Turns on CDP globally. (On by default)

Router(config)#no cdp run

Turns off CDP globally.


Miscellaneous Commands
Show detail status of interfaces

R1#show controllers ?
  Async Async UART internal info
  Async Async interface
  E1 E1 controller internal state
  FastEthernet FastEthernet IEEE 802.3
  J1 J1 controller internal state
  Serial Serial
  T1 T1 controller internal state
  T3 T3 controller internal state
  XTagATM Extended Tag ATM interface
  vsi VSI information
  |             Output modifiers
  <cr>

To find out if the connected serial interface is DCE or DTE?

R1#show controllers serial 0/1
Interface Serial0/1
Hardware is GT96K
DCE 530, clock rate 2000000
idb at 0x65F84D48, driver data structure at 0x65F8C454
wic_info 0x65F8CA80
Physical Port 0, SCC Num 0
<Output Omitted>

To configure the clock rate on serial interfaces

R1#config t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface serial 0/1
R1(config-if)#clock rate 64000

To set the bandwidth (This is not the physical bandwidth, mainly for routing protocol calculation)

R1(config-if)#bandwidth 640

That’s the list! Like before these are the most common and are usually used in the CCNA area when troubleshooting. If you want to find more information check out Cisco documentation and like always I hope this was informative and if you have an idea on the next topic that deals with ICND1 or ICND2 let me know. :)

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