Basic About Routers and Switches Modes

I have Publish a number of Post about Computer Networking. Today I wrote this Post about CCNA.
In this Post, I will give you a short introduction to the Cisco Internetwork Operating System, also known as the IOS. This is the operating system that controls Cisco routers and switches and provides the interface to configure Cisco devices as well.

We will take a look at the various router command modes, set router passwords and banners, configure router hostnames and interface descriptions, and much more.

Overview of Router Modes :

1. User/Enable mode :
Once you login into a router you instantly enter the so-called user mode – the prompt [Router name] > appears. From this mode you can only see some statistic information.

2. Privileged mode :
To view and change the configuration of the router you have to enter into the privileged mode by entering the enable command. Here are the steps:

RouterA>
    RouterA>enable
    RouterA#

3. Global/Configuration Mode :
To be able to make global changes to the configuration of the router you have to enter the global configuration mode. Once you achieve that, you are able to access any possible subsequent configuration mode and make global changes:

    RouterA#configure terminal or config t for short
    RouterA(config)#

Now you have the control of your device. If you need to modify your router’s configuration then you enter the appropriate configuration mode. For example, if you want to make a change to your Fastethernet interface 0/0 then you have to enter interface configuration mode and make your modifications from there. Here are the steps:

RouterA(config)# interface fastethernet 0/0
    RouterA(config-if)#

Prompt RouterA(config-if)# indicates you are in interface configuration mode. At any time, and any mode you are in, you can insert a question mark ? and the router will automatically show all the possible commands or option parameters you can apply at that specific time.

RouterA(config-if)# ?

Interface configuration commands:

access-expression    Build a bridge boolean access expression
arp                  Set arp type (arpa, probe, snap) or timeout
backup               Modify backup parameters
ip                   Interface Internet Protocol config commands .
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Below there is a list of the most important configuration modes along with the commands used to enter these modes: