Cisco Router Hardware Software overview

In this lecture we will investigate an In this lecture we will investigate an overview of Cisco router hardware and overview of Cisco router hardware and software. We will first turn our attention to software. We will first turn our attention to the basic hardware components of a Cisco the basic hardware components of a Cisco router. router.

Basic Hardware Components

Central Processing Unit (CPU)Central Processing Unit (CPU) Flash MemoryFlash Memory Read-Only Memory (ROM)Read-Only Memory (ROM) Random-Access Memory (RAM)Random-Access Memory (RAM) Non-volatile RAM (NVRAM)Non-volatile RAM (NVRAM) Input/Output (IO) Ports and Media-Input/Output (IO) Ports and Media-

Specific ConvertersSpecific Converters

Central Processing Unit (CPU)

The central processing unit (CPU), or The central processing unit (CPU), or microprocessor, executes instructions that microprocessor, executes instructions that make up the router’s operating system, as make up the router’s operating system, as well as user commands entered via the well as user commands entered via the console or via a Telnet connection. Thus, console or via a Telnet connection. Thus, the processing power of the CPU is directly the processing power of the CPU is directly related to the processing capability of the related to the processing capability of the router.router.

Flash Memory

Flash memory is an erasable, reprogram Flash memory is an erasable, reprogram able type of ROM memory. On many able type of ROM memory. On many routers flash memory is an option that can routers flash memory is an option that can be used to retain an image of the operating be used to retain an image of the operating system and the router’s micro codesystem and the router’s micro code

Read-Only Memory (ROM)

Read-only memory (ROM) contains code Read-only memory (ROM) contains code that performs power-on diagnostics similar that performs power-on diagnostics similar to the power-on self-test (POST) many PCs to the power-on self-test (POST) many PCs performperform

Random-Access Memory (DRAM)

Random-access memory (RAM) holds Random-access memory (RAM) holds routing tables, performs packet buffering, routing tables, performs packet buffering, furnishes an area for the queuing of packets furnishes an area for the queuing of packets when they cannot be directly output due to when they cannot be directly output due to too much traffic routed to a common too much traffic routed to a common interface, and provides memory for the interface, and provides memory for the router's configuration file when the device router's configuration file when the device is operationalis operational

Non-volatile RAM (NVRAM)

Non-volatile RAM (NVRAM) retains its Non-volatile RAM (NVRAM) retains its contents when a router is powered off. By contents when a router is powered off. By storing a copy of its configuration file in storing a copy of its configuration file in NVRAMNVRAM

Input/Output (IO) Ports and Media-Specific Converters

The input/output (I/O) port is the The input/output (I/O) port is the connection through which packets enter and connection through which packets enter and exit a routerexit a router

The Router Initialisation Process

Basic Software Components

Operating System ImageIOS

The operating system image consists of a The operating system image consists of a series of routines that supports the transfer series of routines that supports the transfer of data through the device, manages buffer of data through the device, manages buffer space, supports different network functions, space, supports different network functions, updates routing tables, and executes user updates routing tables, and executes user commands.commands.

Configuration File

This file is created by the router administrator and This file is created by the router administrator and contains statements interpreted by the operating contains statements interpreted by the operating system that tell it how to perform different system that tell it how to perform different functions built into the OSfunctions built into the OS

Once the configuration file is saved, it is stored in Once the configuration file is saved, it is stored in the NVRAM and loaded into upper-addressed the NVRAM and loaded into upper-addressed memory each time the router is initialisedmemory each time the router is initialised

The Router Configuration Process

The first time you take a router out of the The first time you take a router out of the box and power it on, or after you add one or box and power it on, or after you add one or more hardware components, you must use more hardware components, you must use the setup commandthe setup command

Cabling Considerations

The system console port on a router is The system console port on a router is configured as a data terminal equipment configured as a data terminal equipment (DTE) port(DTE) port

A crossover cable is needed, where pin 2 at A crossover cable is needed, where pin 2 at one end is crossed to pin 3 on the other end one end is crossed to pin 3 on the other end and vice versaand vice versa

Console Access

A variety of communications programs are A variety of communications programs are available for accessing the router via its available for accessing the router via its console port. Since Windows95 and console port. Since Windows95 and Windows98 include the HyperTerminal Windows98 include the HyperTerminal communications programcommunications program

Setup Considerations

The Command InterpreterThe Command Interpreter Referred to as the EXECReferred to as the EXEC user and privilegeduser and privileged modes modes

User EXEC mode = “>” prompt

When you log into the router, you are in the user When you log into the router, you are in the user command mode where the system prompt appears command mode where the system prompt appears as an angle bracket (>). as an angle bracket (>).

By logging into the router, you access By logging into the router, you access user EXECuser EXEC commands that allow you to connect to another commands that allow you to connect to another host, provide a name to a logical connection, host, provide a name to a logical connection, change the parameters of a terminal, display open change the parameters of a terminal, display open connections, and perform similar operations that connections, and perform similar operations that are not considered critical operations by Cisco are not considered critical operations by Cisco SystemsSystems..

USER MODE OPERATIONS

Privileged EXEC mode

Accessed by “enable” command and or Accessed by “enable” command and or password.password.

““#” prompt indicates you are at the #” prompt indicates you are at the privileged modeprivileged mode

Allows the following featuresAllows the following features

Privileged EXEC mode “#”

                configuration information, configuration information,                 turn privileged commands on or off, turn privileged commands on or off,                 lock the terminal, and lock the terminal, and                 perform other critical functions. perform other critical functions.

Configuration Command CategoriesConfiguration commands can be categorized into Configuration commands can be categorized into

four general categories:four general categories: (1)   global, which defines system wide (1)   global, which defines system wide

parameters; parameters; (2)   interface, which defines WAN or LAN (2)   interface, which defines WAN or LAN

interfaces; interfaces; (3)   line, which defines the characteristics of a (3)   line, which defines the characteristics of a

serial terminal line; and serial terminal line; and (4)   router subcommands, which are used to (4)   router subcommands, which are used to

configure a routing protocol.configure a routing protocol.

GLOBAL CONFIGURATION COMMANDS

Global configuration commands are used to Global configuration commands are used to define system wide parameters, including define system wide parameters, including access listsaccess lists..

INTERFACE COMMANDS

define the characteristics of a LAN or WAN define the characteristics of a LAN or WAN interface and are preceded by an interface interface and are preceded by an interface commandcommand..

interface serial 0interface serial 0