Commands can be executed in Cisco IOS software under access modes: User and Privileged. The commands in the User mode is in a way, a low level access version of the Privileged mode.
The below table explains the different modes, what can be done in these modes and the prompt telling you which mode you are in.
User mode: You enter this mode when you start a router. You can see ‘Router>’ prompt. Command like ‘ping, telnet, and rlogin’ run in this mode, also you can get information regarding the IOS if you type ‘show version’. So this mode gives you information but does not let you make any modification in the configuration. For any configuration or modification of the router you have to enter into the privileged mode by giving the command ‘enable’
Privileged mode: You will be prompted to enter a password in order to access this mode (while configuring a router for the first time, the password for the privileged mode can be avoided but that’s a security risk). You can modify the router configuration, the interfaces on the router or create an initial configuration following the sub-modes.
In order to make things easier, the sub modes can be identified from the prompt. For example, the privileged mode shows ‘router#’ and if you enter the command ‘configure terminal’ here, the prompt changes to ‘router (config) #’, so this tells you that you are in the ‘Global Configuration Mode’
A list of every command that run in each mode can be displayed by entering ‘?’ while in that particular mode, so this makes things a lot easier. Also you don’t have to type every command, you just have to type the first few letters and let the IOS auto-complete it.
Example: Instead of typing ‘Router#configure terminal’ you can type ‘Router#conf ter’
There are a few Hot Keys that will help you work faster while working on Cisco IOS,
| CTRL A | Moves cursor to the beginning of the line |
| CTRL E | Moves cursor to the end of the line |
| CTRL B | Moves cursor back one character |
| CTRL F | Moves cursor forward one character |
| ESC B | Moves cursor back one word |
| ESC F | Moves cursor forward one word |
| CTRL D | Delete one character |
| Backspace | Delete one character to the left of cursor |
| CTRL R | Redisplays a line |
| CTRL V | Erases a line |
| CTRL W | Erases a word |
| Ctrl Z | Exits configuration mode |
| TAB | auto completes partially entered word |
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