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> enable | switches to privileged EXEC level |
| Router# configure terminal | switches to global configuration level |
| Router(config)# enable secret mypassword | configures 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 ethernet0 | switches to configure the ethernet0 interface |
| router(config-if)# ip address <ip address> <subnet> | configures an IP address on ethernet0 (interface) |
| Router(config-if)# no shutdown | activates ethernet0 (interface) (if required) |
| Router(config-if)# exit | exits back to global configuration level |
| Router(config)# interface serial0 | switches 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 shutdown | activates serial0 (interface) (if required) |
| Router(config-if)# exit | exits back to global configuration level |
| Router(config)# ^Z | CTRL-Z exits out of configuration level |
| Router# copy running-config startup-config | saves configuration into NVRAM |
| Router# disable | disables 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 ethernet0 | switches 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 Arrow | Allows user to scroll backward through former commands. |
Helpfull Links:
- Cisco's IOS Command Line Interface Tutorial - Straight from the horse's mouth.
- IOS Commands Master List
- Password Recovery on 1600
- RomMon Recovery on 1600
- Subnetting Notes