Cisco’s Internetworking Operating System (IOS)

Topic: - Cisco’s Internetworking Operating  System (IOS)

The Cisco Internetwork Operating System (IOS) is the kernel of Cisco routers as well as all current Catalyst switches. A kernel is the elemental, indispensable part of an operating system that allocates resources and manages tasks like low-level hardware interfaces and security.

The Cisco IOS is a proprietary kernel that provides routing, switching, internetworking, and telecommunications features. The first IOS was written by William Yeager in 1986 and enabled networked applications.

Responsibility of Cisco's Router IOS:-

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1. Carrying network protocols and functions
2. Connecting high-speed traffic between devices
3. Adding security to control access and stop unauthorized network use
4. Providing scalability for ease of network growth and redundancy
5. Supplying network reliability for connecting to network resources
6. The core function of Cisco IOS is to enable data communications between network nodes

Types of IOS operating systems:-

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1. IOS XE -  runs on top of a Linux kernel. IOS XE  and IOS share a lot of the same code, but IOS XR is considered to be a completely different code base. 
2. IOS XR -  based on QNX a commercial Unix-like real-time operating system. IOS XR supports software-defined networking (SDN) and the embedded systems market.

Administrative Configuration:-

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You can configure the following administrative functions on a router and switch:

1. Hostnames
2. Banners
3. Passwords
4. Interface descriptions

Hostnames:) We use the hostname command to set the identity of the router. This is only locally significant, meaning it doesn’t affect how the router performs name lookups or how the device actually works on the internetwork. But the hostname is still important because it’s often used for authentication in many wide area networks (WANs).    Router#configure terminal

Router(config)#hostname abhishek

abhishek(config)#

Banners:) A banner is a message that is presented to someone using the router. The type of banner you configure determines when this message is shown to the user. You can configure three main types of banners on a Cisco router. 

1. Exec  process creation banner
2. User Login banner 
3. Message  of the day banner

Message of the day (MOTD) banners are the most widely used banners because they give a message to anyone connecting to the router via Telnet or an auxiliary port or even through a console port as seen here: 

User Login Banner; You can configure a login banner for display on all connected terminals.It will show up after the MOTD banner but before the login prompts.

EXEX Banner; You can configure a line-activation (exec) banner to be displayed when EXEC processes such as a line activation or an incoming connection to a VTY line have been created. Simply initiating a user exec session through a console port will activate the