Cisco IOS
Every router uses the operation system and the OS used in router is known as Internetwork operation System (IOS).Similar the operating system of the computer Cisco IOS is responsible to manage the hardware and software resources of the router. It is a multitasking operating system that is integrated with routing, switching, and internetworking and telecommunications functions. The Cisco IOS was created to deliver the network services and applications. It runs on most Cisco router. It carries different network protocols and functions The Cisco IOS is also provide the security to control access and stop the unauthorized network use.
An IOS image is a file that contains the entire IOS for the router. Cisco creates many different IOS images that are depends on the model of the router and the feature of the IOS.Some additional feature require more flash and RAM memory to store and load the IOS.For example some Cisco IOS has the ability to run IPV6 or the link state protocol –Intermediate system-to-Intermediate system (IS-IS).Cisco router has its own interfaces and the CLI (Command Line Interfaces) is a common method of configuring Cisco routers.
In all the version of the Cisco router packet forwarding and routing are the distinct functions. There are some basic modes of the Cisco router –
1. User execution mode-Its mostly used to view statistics. This mode is shows in the router like this-
Router>
2. Privilege mode-From this mode we can perform the following task-
We can copy RAM.NVRAM and IOS file.
We can delete RAM, NVRAM and IOS
We can reboot router.
The privilege mode shows in router like this-
Router#
3. Global configuration mode-We can change any configuration and do the modification in this mode. We can type ‘config’ from the privilege mode prompt and then press Enter. This command shows as –
Router (config) #
To change the running configuration we use the configure terminal. During the boot up process the startup-config file in NVRAM is copied into RAM and store as running-config file. Changes in the configuration are stores in the running-config file and implemented by the Cisco IOS.
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