Introduction to Cisco IOS (Cisco Internetwork Operating System)
Home networks typically interconnect a wide variety of end devices including PCs,
laptops, tablets, smartphones, smart TVs, Digital Living Network Alliance (DLNA)
compliant network media players (such as Xbox 360 or PlayStation 3), and more.
All of these end devices are usually connected to a home router. Home routers are
actually four devices in one:
Router: Forwards data packets to and and receives data packets from the Internet
Switch: Connects end devices using network cables
Wireless access point: Consists of a radio transceiver capable of connecting end devices wirelessly
Firewall appliance: Secures outgoing traffic and restricts incoming traffic
In larger business networks with significantly more devices and traffic, these devices
are often incorporated as independent, standalone devices, providing dedicated service.
End devices, such as PCs and laptops, are connected to network switches using wired
connections. To send packets beyond the local network, network switches connect to
network routers. Other infrastructure devices on a network include wireless access
points and dedicated security devices, such as firewalls.
Each device is very different in hardware, use, and capability. However, in all cases,
the operating system enables the hardware to function.
Operating systems are used on virtually all end-user and network devices connected
to the Internet. End user devices include devices such as smartphones, tablets, PCs,
and laptops. Network devices, or intermediary devices, are devices used to transport
data across the network and include switches, routers, wireless access points, and
firewalls. The operating system on a network device is known as the network operating system.
The Cisco Internetwork Operating System (IOS) is a generic term for the collection
of network operating systems used on Cisco network devices. Cisco IOS is used for
most Cisco devices regardless of the type or size of the device.
Purpose of OS
Network operating systems are in many ways similar to the operating systems of PCs.
An operating system performs a number of technical functions "behind the scenes"
that enable a user to
• Use a mouse
• View output on a monitor
• Enter text commands
• Select options within a dialog box
• Manage hardware processes
The shell functions for switches and routers are very similar. These shell functions
of the IOS on a switch or router, which take place "behind the scenes," provide the
network technician with an interface. The technician can enter commands to configure,
or program, the device to perform various networking functions. The IOS operational
details vary on internetworking devices, depending on the purpose of the device and
the features supported.
There are many distinct variations of Cisco IOS:
• IOS for switches, routers, and other Cisco networking devices
• IOS numbered versions for a given Cisco networking device
• IOS feature sets, providing distinct packages of features and services
Just as a PC might be running Microsoft Windows 8 and a MacBook might be running OS X,
a Cisco networking device runs a particular version of the Cisco IOS. The version of
IOS is dependent on the type of device being used and the required features. While all
devices come with a default IOS and feature set, it is possible to upgrade the IOS version
or feature set to obtain additional capabilities.