Transcript Router Basics

Cisco Router Hardware
Software overview

In this lecture we will investigate an
overview of Cisco router hardware and
software. We will first turn our attention to
the basic hardware components of a Cisco
router.
Basic Hardware Components
Central Processing Unit (CPU)
 Flash Memory
 Read-Only Memory (ROM)
 Random-Access Memory (RAM)
 Non-volatile RAM (NVRAM)
 Input/Output (IO) Ports and MediaSpecific Converters

Central Processing Unit (CPU)

The central processing unit (CPU), or
microprocessor, executes instructions that
make up the router’s operating system, as
well as user commands entered via the
console or via a Telnet connection. Thus,
the processing power of the CPU is directly
related to the processing capability of the
router.
Flash Memory

Flash memory is an erasable, reprogram
able type of ROM memory. On many
routers flash memory is an option that can
be used to retain an image of the operating
system and the router’s micro code
Read-Only Memory (ROM)

Read-only memory (ROM) contains code
that performs power-on diagnostics similar
to the power-on self-test (POST) many PCs
perform
Random-Access Memory
(DRAM)

Random-access memory (RAM) holds
routing tables, performs packet buffering,
furnishes an area for the queuing of packets
when they cannot be directly output due to
too much traffic routed to a common
interface, and provides memory for the
router's configuration file when the device
is operational
Non-volatile RAM (NVRAM)

Non-volatile RAM (NVRAM) retains its
contents when a router is powered off. By
storing a copy of its configuration file in
NVRAM
Input/Output (IO) Ports and
Media-Specific Converters

The input/output (I/O) port is the connection
through which packets enter and exit a
router
The Router Initialisation
Process
Basic Software Components
Operating System Image
IOS

The operating system image consists of a
series of routines that supports the transfer
of data through the device, manages buffer
space, supports different network functions,
updates routing tables, and executes user
commands.
Configuration File


This file is created by the router administrator and
contains statements interpreted by the operating
system that tell it how to perform different
functions built into the OS
Once the configuration file is saved, it is stored in
the NVRAM and loaded into upper-addressed
memory each time the router is initialised
The Router Configuration
Process

The first time you take a router out of the
box and power it on, or after you add one or
more hardware components, you must use
the setup command
Cabling Considerations
The system console port on a router is
configured as a data terminal equipment
(DTE) port
 A crossover cable is needed, where pin 2 at
one end is crossed to pin 3 on the other end
and vice versa

Console Access

A variety of communications programs are
available for accessing the router via its
console port. Since Windows95 and
Windows98 include the HyperTerminal
communications program
Setup Considerations
The Command Interpreter
 Referred to as the EXEC
 user and privileged modes

User EXEC mode = “>” prompt


When you log into the router, you are in the user
command mode where the system prompt appears
as an angle bracket (>).
By logging into the router, you access user EXEC
commands that allow you to connect to another
host, provide a name to a logical connection,
change the parameters of a terminal, display open
connections, and perform similar operations that
are not considered critical operations by Cisco
Systems.
USER MODE OPERATIONS
Privileged EXEC mode
Accessed by “enable” command and or
password.
 “#” prompt indicates you are at the
privileged mode
 Allows the following features

Privileged EXEC mode “#”


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

configuration information,
turn privileged commands on or off,
lock the terminal, and
perform other critical functions.
Configuration Command
Categories
Configuration commands can be categorized into
four general categories:
 (1)
global, which defines system wide
parameters;
 (2)
interface, which defines WAN or LAN
interfaces;
 (3)
line, which defines the characteristics of a
serial terminal line; and
 (4)
router subcommands, which are used to
configure a routing protocol.
GLOBAL CONFIGURATION
COMMANDS

Global configuration commands are used to
define system wide parameters, including
access lists.
INTERFACE COMMANDS

define the characteristics of a LAN or WAN
interface and are preceded by an interface
command.

interface serial 0