Modes
Configuration mode is also called “Global” Configuration Mode
NOTE: the first two levels, User & Priviledged, use the router’s “EXEC Command Interpreter”. The config and extended modes do not.
User Mode (User Exec mode) - very basic, rarely used mode, for checking router status and basic system info. You cannot view the router config from user mode!! For regular router usage there is no login required for this mode – however for console access via laptop cable there is a password.
Priviledged Mode (Priviledged Exec, or Enable mode) – this mode allows you to view extensive info about the router’s config, and also allows you to change some of the config parameters. It is also a gateway for getting into the config mode and it’s associated extended modes. This mode can be set up with a login password if desired.
Config mode - . The config mode is actually only a temporary gateway mode to get to extended modes. Very little can be done in the config mode.
config t –config terminal - this command causes you to enter config mode with the most common option, the “terminal” option
config mem - config memory – the old way of doing a “copy start run” - rarely used –
config net –config network – same as “copy tftp run” - rarely used - loads the config from a TFTP host into DRAM and allows you to then make changes to that config
Extended Config modes – Cisco has no term for these modes and simply calls them “config” modes. Cisco Press calls the commands that take you there, “context setting” commands. The standard config mode is called “Global Config”. The point is, most of the commands in Config mode take no action other than to tell the router what extended mode you want. When you go to an extended mode, the prompt changes.
The Int command is by far the most common context-setting config command, and takes you to an extended mode which is often called “Interface Configuration mode” with the prompt:
Router(config) # int s0
Router (config-if) #
Another extended mode is when configuring the lines (to add a password for example), and the line command takes you to the prompt :
Router (config) # line con 0
Router (config-line) #
Another extended mode is configuring an interface for RIP or IGRP routing protocol:
Router (config) # router rip OR router igrp 10
Router (config-router) # network 172.16.0.0
For example, if you are in config mode with the router prompt “router(config)#”, and you type “int s0” or “int e0”so that you can configure the Serial 0 or Ethernet 0 interface - the prompt changes to “router(config-if)#”, “interface” mode”. Unfortunately the prompt does not remind you whether you are in the serial, ethernet, or fast ethernet interface mode. It is the same for all three. The context setting command, int s0, in config mode changes nothing, but it takes you to the extended mode, where you can change things . . . assign an IP address to the interface, etc. This is only one example of several extended modes.
Moving between extended config modes – you enter an extended mode by issuing a context setting command such as e0. To get to another extended mode you do not need to go back to config mode and then enter the new context setting command. You can switch directly between the extended modes. For this example, to go from int e0 mode to the serial interface mode, simply type “int so”.
en (enable) – moves you from User to Priveledged mode. User mode is similar to a guest account, since the commands will not change anything. Priveledged mode allows what are called “disruptive commands”, since they could mess up the router operation if misused.
int – this context setting command is followed by the name of the interface – e0 (Ethernet 0), E1 (Etherent 1), etc. and s0 (Serial 0), s1 (Serial 1), etc.
EXEC - the command interpreter for user and priveledged mode is called EXEC. User and Priveledged modes are often called “User Exec” and “Priveledged Exec
Non-Destructive Commands – User EXEC commands such as basic tests, listing system info, etc.
Destructive Commands – Priveledged EXEC or Config mode commands, that can change the operation of the router, and if not handled with care, can be potentially destructive. Therefore it is recommended to password protect the Priveledged level. The config level does not need password protection, since you must first get to priveledged mode.
User EXEC vs Priveledged EXEC vs Config mode – User mode only allows you to view certain things about the router and is similar to “Read-Only” mode. Priveledged mode allows you to issue “show” commands which list the router’s configuration. However Priveledged mode does not have many destructive commands. Config mode is where you actually make chages to the router’s configuration – and each change is stored in DRAM. To tell what mode a particular command is used for – remember that any command used to configure the router is a config mode command, and most of the other commands are priveledged mode (including all show commands). The User commands you will just have to memorize.
NOTE: You will spend most of your time in privileged and configuration modes, since you cannot change the router config from user mode. The “config t” command takes you into configuration mode in “terminal” mode. You can simply type “config” but will then be presented with several options, the default one being “terminal” (the other two config options are rarely used).
- the following prompts let you know which mode you are in :
Router> (user mode)
Router# (privileged mode)
Router(config)# (configuration mode – several types, the typical is “terminal”)
Router(config-if)# (configuration interface mode – whether “int s0” or “int e0”, or f0/0 – you will still see the same prompt). This is one of several config “extended modes”.
The first word of the prompt is always the hostname, which is router by default. For example, if I issued the command to change the hostname, you can see how the prompt changes:
Router(config) # hostname Ken
Ken(config) #
There are other modes, such as “rommon” - ROM Monitor Mode (the prompt is simply > or rommon> ), Setup Mode (no prompt, just text asking you to enter a response), RX Boot Mode (the prompt is Router<boot>, and the many Configuration modes which we called “extended modes” (more than 17 of them). Config Interface mode is just one of many (such as config modes to create multiple virtual interfaces (subinterfaces) onto one physical interface, initialize a routing protocol such as RIP, etc.
rommon (ROM monitor) mode – a rudimentary command structure, used for manufacturing testing and troubleshooting, and can be used to for password recovery. To get into the rommon mode, turn the router off then on, and press the break key within the first 60 seconds. The prompt will then be: rommon>
Setup mode – similar to Config mode, but it asks you a series of questions. It is also much more basic, and rarely used. Can be entered by typing “setup” in Priveledged mode, or if NVRAM is empty during boot-up (the router asks you if you want to enter the “initial configuration dialog”). It interactively asks you a number of basic questions such as host name, routing protocol, ip addresses to be assigned to interfaces, etc. It then creates a basic config file which is then stored in both DRAM and NVRAM. Next time the router is rebooted, the setup mode is skipped and you will go directly to User Exec mode.