Cisco Internetworking Operating System

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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 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. In the next lab, you will learn how to move between different prompts on a Cisco router. 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 Internetworking Operating System (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.

Hope you got the basic of Cisco IOS

Manolis Skoras is a Cisco, Microsoft and HP Certified Trainer and systems-network engineer. Recently he created a site with How to study For CCNA, Study Quides to help his students and people around the world to better understand the material they will be tested on, thus having greater success rates. Check Certify4Sure today


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