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Cisco IOS Notes

Some quick notes on Cisco Internetworking Operating System (IOS).

Connecting via console:

9600 baud
No parity
8 data bits
1 stop bit
no flow control

Taking Interfaces Out Of Shutdown
Routers ship from the factory with all interfaces deactivated. Deactivated interfaces are referred to as being in a shutdown state. Before an interface can be used, it must be taken out of the shutdown state. To take an interface out of shutdown, type "no shutdown" at the appropriate interface configuration level. The example below includes these commands for both the ethernet and serial interfaces.

Changing IP Address:

Router> enableswitches to privileged EXEC level
Router# configure terminalswitches to global configuration level
Router(config)# enable secret mypasswordconfigures router with an enable secret (global)
Router(config)# ip route 0.0.0.0 0.0.0.0 <destination ip>configures a static IP route (global)
Router(config)# interface ethernet0switches to configure the ethernet0 interface
router(config-if)# ip address <ip address> <subnet>configures an IP address on ethernet0 (interface)
Router(config-if)# no shutdownactivates ethernet0 (interface) (if required)
Router(config-if)# exitexits back to global configuration level
Router(config)# interface serial0switches to configure the serial0 interface
Router(config-if)# encapsulation <hdlc, ppp, etc.>Set encapsulation
Router(config-if)# ip address <ip address> <subnet>configures an IP address on serial0 (interface)
Router(config-if)# no ip directed-broadcast 
Router(config-if)# description T1, circuit ID#, Customer #  Assigns a general discription to interface
Router(config-if)# no shutdownactivates serial0 (interface) (if required)
Router(config-if)# exitexits back to global configuration level
Router(config)# ^ZCTRL-Z exits out of configuration level
Router# copy running-config startup-configsaves configuration into NVRAM
Router# disabledisables privileged EXEC level
Router>indicates user is back to user EXEC level

Removing Commands / Resetting Default Values
Cisco IOS provides an easy way to remove commands from a configuration. To remove a command from the configuration, simply navigate to the proper location and type "no" followed by the command to be removed. The following example displays how to remove an IP address from the ethernet0 interface.

Router> enable switches to privileged EXEC level
Router# configure terminal switches to global configuration level
Router(config)# interface ethernet0switches to configure the ethernet0 interface
Router(config-if)# no ip address removes IP address
Router(config-if)# exit exits back to global configuration level
Router(config)# exit exits out of configuration level
Router# disable disables privileged EXEC level
Router> prompt indicates user is back to user EXEC level


Saving your work:
Prior to IOS version 11.x:Router# write memory
IOS version 11.x and newer:Router# copy running-config startup-config

Shortcut keys:
Delete Removes one character to the right of the cursor.
Backspace Removes one character to the left of the cursor.
TAB Finishes a partial command.
Ctrl-A Moves the cursor to the beginning of the current line.
Ctrl-R Redisplays a line.
Ctrl-U Erases a line.
Ctrl-W Erases a word.
Ctrl-Z Ends configuration mode and returns to the EXEC.
Up Arrow Allows user to scroll forward through former commands.
Down ArrowAllows user to scroll backward through former commands.

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