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Wednesday, November 16, 2011

How to configure a Router and what is Cisco IOS?

Now a days,every company maintains standard operating systems.For example, IBM uses Citrix Net scaler OS and Cisco uses its won IOS(Internetwork Operating System).In older posts,we studied what is a router and cisco heirarchical model.Everyone goes on studying and studying.....for Cisco exams (e.g.CCNT,CCNA,CCNP and CCIE etc) but how many are confident to show router startup.???
Here I am giving the techniques of router startup and it's configuration.

Router Startup:
  • Boot process steps 
  • Test hardware 
  • Load bootstrap program 
  • Locate and load the Cisco IOS 
  • Locate and load the router configuration file


Introduction to Cisco IOS?

-Almost all current Cisco routers and switches run Cisco IOS (Internetwork Operating System),

the routing and switching software in Cisco devices.

- Cisco IOS command-line interface (CLI) is the text-based user interface to a Cisco device for

configuring, administering, and managing the Cisco device.

- CLI can be accessed through:

i) Console with a rollover cable and terminal emulator application. [line console 0]

ii) AUX through a dialup device such as modem for out-of-band management. The modem

is connected with a straight-through cable to the auxiliary port. [line aux 0]

iii) In-band management through the network via Telnet or SSH. [line vty 0 4]

- Below lists the main Cisco IOS modes:

User EXEC mode: Least privileges and limited access. Only provides a set of nondestructive show commands that allow examination of configuration.

Privileged mode: More show commands, and limited configuration commands.

Configuration mode: Configuration commands are being entered in this mode. Unable to check status with the series of show commands. Sub-divided into some child modes.
eg: interface configuration mode, line configuration mode, router configuration mode, etc.
         Commands entered in this mode update the active or running configuration immediately after the Enter button is pressed.
         Configuration commands can be divided into global configuration commands and sub-commands, eg: interface sub-command,sub-interface subcommand, controller subcommand, line sub-command,router subcommand, etc.

- Below describes some basic Cisco IOS commands:

enable - Switches from EXEC mode to Privileged mode

disable - Switches from Privileged mode back to EXEC mode.

show version - Views the basic configuration of the system hardware, software version, the name and source of the system boot image, etc.

configure terminal - Switches from Privileged mode to Global Configuration mode.

hostname -Changes the hostname of a Cisco device.

^Z / end / exit -Exits from the Global Configuration mode back to Privileged mode.

exit / quit - Exits from the EXEC mode.

- Some special IOS CLI features are Context-Sensitive Help with [?] and Auto-Completion with
[TAB] can be used to display or auto-complete the available commands or parameters.

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