CCNA2 Chapter 2

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CCNA2 Chapter 2
Cisco IOS Software
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Cisco IOS Software

• Ciscos operating system is called Cisco
  Internetwork Operating System (IOS)
• IOS provides the following network services
• basic routing and switching functions
• reliable and secure access to networked
  resources
• network scalability

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Access to Routers

• Cisco IOS software uses a command-line interface
  (CLI) as the console environment.
• This environment is accessible via
• console session
• Uses a low speed serial connection directly from
  PC to router
• AUX port
• Dialup with a modem through AUX port. Dont need
  the router to be connected to network services
• Telnet
• Must have at least one interface configured with
  IP address, and virtual terminal sessions must be
  configured for login password.

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Cisco IOS Software

• The Cisco CLI uses a hierarchical structure,
  called modes.
• The IOS provides a command interpreter service
  known as the command executive (EXEC).
• For security reasons, Cisco routers have two
  access levels
• user EXEC mode
• Has limited number of basic monitoring commands.
• This mode is identified by gt (Example
  Routergt)
• privileged EXEC
• Requires password
• May require an user ID
• Users can accesses all router commands
• This mode is identified by (Example Router)

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Cisco IOS Software

• Cisco IOS releases naming convention contain 3
  parts
• platform on which the image runs
• special features supported in the image
• where the image runs and whether it has been
  zipped or compressed

• It is of the form xxxx-yyyy-ww
• xxxx Platform
• yyyy Features
• ww Format where it executes

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Cisco IOS Software
Before installing a new Cisco IOS software image
on the router, check to see if the router meets
the memory requirements. Use the command show
version
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Cisco IOS Software

• To find out amount of flash memory, use the
  command show flash

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Router Commands

• show version command displays
• IOS version and descriptive information
• bootstrap ROM version
• boot ROM version
• router up time
• last restart method
• system image file and location
• router platform
• configuration register setting (how IOS is
  booted)

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IOS version

• Platform
• Feature set
• Location to be used for loading the IOS

Boot ROM version
Router up time
System image file location
Last restart method
Number type of interfaces on the router
Configuration register setting
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This command will show all of the Cisco IOS image
files not just the one that the router booted
from. Might compare to a directory listing
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Cisco IOS Software
Cisco IOS has 3 distinct operating environments
or modes

• ROM monitor
• Performs the bootstrap processProvides low-level
  functionality and diagnostics. Used for
  password recovery. Can NOT be accessed through
  any interface.

• Boot ROM
• Only a limited subset of Cisco IOS features are
  available. One is allowed to write to flash
  memory is used primarily to replace the Cisco
  IOS image stored in flash

• Cisco IOS
• Needs the full IOS image as stored in flash

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Initial Startup
The major steps in initialization of a router
are

• Power up self test (POST)

• Bootstrap loader in ROM executes

• Locate and load the operating system

• Locate and load the configuration files

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Initial Startup

• Bootstrap loader
• Simple set of instructions that tests hardware
  and initializes the IOS

• Locate and load IOS (determined where by the
  configuration register stored in NVRAM (if
  indicates Flash, then looks for boot system
  comands if none, the default is)

• Flash

• TFTP server

• ROM

• locate and load configuration files

• NVRAM

• TFTP server

• Console

If no TFTP server is found, then the setup dialog
is initiated.
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Setup Mode

• Setup mode is not intended to be used to enter
  complex protocol features in a router.
• The purpose of the setup mode is to permit
  administrators to install a basic configuration
  for routers when a configuration cannot be
  obtained from another source.
• In the setup mode, default answers appear in
  square brackets following the question.
• Pressing the Enter key accepts these defaults.
• During the setup process, Ctrl-C can be pressed
  at any time to terminate the process.

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Setup Mode

• The router will enter setup mode when
• The contents of NVRAM have been erased with the
  erase start command
• The router is out of the box and has not been
  initially configured
• After deleting the backup configuration and
  reloading the router
• You can make the router enter setup mode by
  entering
• Routersetup

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Initial Startup
After the system initializes correctly, the LED
to the right of the AUX port will become green.
(2600 light is in the front)
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HyperTerminal
The default parameters for the console port are

• console port 9600 baud

• data bits 8

• no parity

• 1 stop bit

• no flow control

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Router Modes

• User (User EXEC) mode Routergt
• Privilege mode Router

• Global configuration mode Router
  config t
• Only accessible from the privilege mode.
• From this mode one can access
• interfaces
• sub interfaces
• line
• router
• router-map

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Router HELP commands
? Ctrl-A moves to the beginning of the command
line Esc-B move back one word Ctrl-B move
back one character (left arrow) Ctrl-E move to
the end of the command line Ctrl-F move forward
one character (right arrow) Esc-F move forward
one word Ctrl-P recalls last or previous
command (up arrow) Ctrl-N recalls most recent
command (down arrow) ltTabgt - complete the entry
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Using the Help System
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Router HELP commands
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Router Command History
Maximum number of commands in the history buffer
is 256