Cisco IOS (Internetworking Operating System)
Now about the CLI (command line interface), you enter configurations for routers and switches
by typing them in, on a console screen. You enter a command and press (Return - enter) and then
do it again for all the following commands. Several words can be entered on the same line.
Cisco IOS (Internetworking Operating System) lesson materials contain really a lot of
pictures and step-by-step instructions that will help you understand all the learning topics
very well, even if you do not use a network simulator. However, I strongly recommend you
to download and learn how to use the free Cisco Packet Tracer simulator, because this way
you will also be able to follow my labs and after gaining the required knowledge, you will
be able to create your own network designs and go deeper to the subjects that are more
important for you.
It is vital to comprehend the different prompts you can find when configuring a router
or switch so you are able to know where you are at any time within configuration mode.
You must check every time your prompts before making any changes to a router's configuration.
You can go to different mode levels interacting with interfaces and devices.
Most commands are mode specific. That means that several commands work in one
mode but not in a different mode. That is why you have to change modes, when you want
to enter a specific command. However, with the do command you can now enter privileged
mode commands in global configuration mode.
Most Cisco IOS commands do not have to be entirely spelled out. To be able to enter
commands faster, you only have to enter part of a command, plus, each word in a command
can be shortened. For example the command enable can be shortened to en. A different
example is the command show running-config. You can just type in sh run. The router or
switch recognizes what you mean and properly understands and carries out that command.
You must type in enough letters for each word in a command for the router or switch
to properly recognize and interpret what you are trying to do. If you do not, you will get
a comment that one or more of your words are ambiguous. This happens because the letters in
one or more of the words in your command can be used to spell out other words also.
Usually after making changes to a device you want to permanently save them, so they are
not lost after rebooting the device. Your running configuration is only in memory and after
a normal reboot or a power failure, running configuration is lost. That is why you must save
your running configurations that exist in DRAM, to the permanently stored startup configurations
that exist in NVRAM.
You can save the configuration file from DRAM to NVRAM by using the command copy
running-config startup-config. Of course you can also use the shortcut command copy run start.
Manolis Skoras has highly developed technical skills in problem identification and implementation
of effective IT solutions. Delivered more than 10.000 technical training hours. How to study For CCNA
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