Routers &Ip Addrrresing

8/6/2019 Routers &Ip Addrrresing

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Routers:-Definition

Router is an internetworkingcomponent or a device that

connects networks which are atdifferent geographical locations.


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Routers

Modular Fixed

Modular Routers:-

These type of routers have upgradable

slots, and the number of ports can beincreased just by adding cards in the

slots.


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Fixed Routers:-

These types of routers

have fixed number of

ports.


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Introduction to RoutersA router is a special type of computer. It has the same basic

components as a standard desktop PC. However, routers are designedto perform some very specific functions. Just as computers need

operating systems to run software applications, routers need the

Internetwork Operating System software (IOS) to run configuration

files. These configuration files contain the instructions and parametersthat control the flow of traffic in and out of the routers. The many

parts of a router are shown below:


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Fixed InterfacesWhen cabling routers for serial connectivity, the routers will either have fixed

or modular ports. The type of port being used will affect the syntax used laterto configure each interface. Interfaces on routers with fixed serial ports are

labeled for port type and port number.


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RAM

Random Access Memory, also called dynamic RAM (DRAM)

RAM has the following characteristics and functions:

Stores routing tables Holds ARP cache

Holds fast-switching cache

Performs packet buffering (shared RAM)

Maintains packet-hold queues

Provides temporary memory for the configuration file of therouter while the router is powered on

Loses content when router is powered down or restarted


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NVRAM

Non-Volatile RAM

NVRAM has the following characteristics

and functions:

Provides storage for the startup

configuration file Retains content when router is

powered down or restarted


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Flash

Flash memory has the following characteristics and

functions:

Holds the operating system image (IOS)

Allows software to be updated without

removing and replacing chips on the processor

Retains content when router is powered down

or restarted

Can store multiple versions of IOS software

Is a type of electronically erasable, programmable ROM

(EEPR

OM)


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ROM

Read-Only Memory

ROM has the following characteristics and functions:

Maintains instructions for power-on self test

(POST) diagnostics

Stores bootstrap program and basic operating

system software

Requires replacing pluggable chips on the

motherboard for software upgrades


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Cisco IOS

Cisco technology is built around the Cisco Internetwork

Operating System (IOS), which is the software that controls

the routing and switching functions of internetworking

devices.

A solid understanding of the IOS is essential for a network

administrator.


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The Purpose ofCisco IOS

As with a computer, a router or switch cannot function without anoperating system. Cisco calls its operating system the Cisco

Internetwork Operating System or Cisco IOS.

It is the embedded software architecture in all of the Cisco routers

and is also the operating system of the Catalyst switches.

Without an operating system, the hardware does not have any

capabilities.

The Cisco IOS provides the following network services:

Basic routing and switching functions

Reliable and secure access to networked resources

Network scalability


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IOS File System Overview


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Initial Startup ofCisco Routers

A router initializes by loading the bootstrap, the operating system, and a

configuration file.

If the router cannot find a configuration file, it enters setup mode.

Upon completion of the setup mode a backup copy of the configuration file may

be saved to nonvolatileRA

M (N

VRA

M).

The goal of the startup routines for Cisco IOS software is to start the router

operations. To do this, the startup routines must accomplish the following:

Make sure that the router hardware is tested and functional.

Find and load the Cisco IOS software.

Find and apply the startup configuration file or enter the setupmode.

When a Cisco router powers up, it performs a power-on self test (POST). During

this self test, the router executes diagnostics from ROM on all hardware modules.


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The show version Command

The show version command displays information about the Cisco IOS softwareversion that is currently running on the router. This includes the configuration

register and the boot field settings.

The following information is available from the show version command:

IOS version and descriptive information

Bootstrap ROM version Boot ROM version

Router up time

Last restart method

System image file and location

R

outer platform Configuration register setting

Use the show version command to identify router IOS image and boot source. To

find out the amount of flash memory, issue the show flash command.


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Router Modes


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User Mode Commands


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Privileged Mode Commands


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Specific Configuration Modes


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CLICommand ModesAll command-line interface (CLI) configuration changes to a Cisco router are made

from the global configuration mode. Other more specific modes are entered

depending upon the configuration change that is required.

Global configuration mode commands are used in a router to apply configuration

statements that affect the system as a whole.

The following command moves the router into global configuration mode

Router#configure terminal (or config t)

Router(config)#

When specific configuration modes are entered, the router prompt changes to

indicate the current configuration mode.

Typing exit from one of these specific configuration modes will return the router

to global configuration mode. Pressing Ctrl-Z returns the router to all the way back

privileged EXEC mode.


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Configuring a Routers NameA

router should be given a unique name as one of the firstconfiguration tasks.

This task is accomplished in global configuration mode

using the following commands:

Router(config)#hostname Tokyo

Tokyo(config)#

As soon as the Enter key is pressed, the prompt changes

from the default host name (Router) to the newly

configured host name (which is Tokyo in the example

above).


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Configuring a Console Password

Passwords restrict access to routers.Passwords should always be configured for virtual terminal lines and

the console line.

Passwords are also used to control access to privileged EXEC mode

so that only authorized users may make changes to the configuration

file.

The following commands are used to set an optional but

recommended password on the console line:

Router(config)#line console 0

Router(config-line)#password

Router(config-line)#login


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Configuring a Modem Password

If configuring a router via a modem you are most likely connected tothe aux port.

The method for configuring the aux port is very similar to

configuring the console port.

Router(config)#line aux 0




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Configuring InterfacesAn interface needs an IP Address and a Subnet Mask to be configured.

All interfaces are shutdown by default.The DCE end of a serial interface needs a clock rate.

Router#config t

Router(config)#interface serial 0/1

Router(config-if)#ip address 200.100.50.75 255.255.255.240

Router(config-if)#clock rate 56000 (required for serial DCE only)Router(config-if)#no shutdown

Router(config-if)#exit

Router(config)#int f0/0

Router(config-if)#ip address 150.100.50.25 255.255.255.0

Router(config-if)#no shutdown

Router(config-if)#exitRouter(config)#exit

Router#

On older routers, Serial 0/1 would be just Serial 1 and f0/0 would be e0.

s = serial e = Ethernet f = fast Ethernet


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Configuring a Telnet Password

A password must be set on one or more of the virtual terminal (VTY)lines for users to gain remote access to the router using Telnet.

Typically Cisco routers support five VTY lines numbered 0 through 4.

The following commands are used to set the same password on all

of the VTY lines:

Router(config)#line vty 0 4




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Examining the show Commands

There are many show commands that can be used to examine the contents of files in the

router and for troubleshooting. In both privileged EXEC and user EXEC modes, thecommand show ? provides a list of available show commands. The list is considerably

longer in privileged EXEC mode than it is in user EXEC mode.

show interfaces Displays all the statistics for all the interfaces on the router. show int

s0/1 Displays statistics for interface Serial 0/1

show controllers serial Displays information-specific to the interface hardwareshow clock Shows the time set in the router

show hosts Displays a cached list of host names and addresses

show users Displays all users who are connected to the router

show history Displays a history of commands that have been entered

show flash Displays info about flash memory and what IOS files are stored there

show version Displays info about the router and the IOS that is running in RAMshow ARP Displays the ARP table of the router

show start Displays the saved configuration located in NVRAM

show run Displays the configuration currently running in RAM

show protocol Displays the global and interface specific status of any configured

Layer 3 protocols


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Introducing Routing

Routing is the process that a router uses to forward packets towardthe destination network. A router makes decisions based upon the

destination IP address of a packet. All devices along the way use the

destination IP address to point the packet in the correct direction so

that the packet eventually arrives at its destination. In order to make

the correct decisions, routers must learn the direction to remotenetworks.


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Configuring Static Routes by Specifying

Outgoing Interfaces


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Configuring Static Routes by Specifying

Next-Hop Addresses


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Administrative Distance

The administrative distance is an optional parameter that gives a measure of thereliability of the route. The range of anAD is 0-255 where smaller numbers are

more desireable.

The default administrative distance when using next-hop address is 1, while the

default administrative distance when using the outgoing interface is 0. You can

statically assign an AD as follows:

Router(config)#ip route 172.16.3.0

255.255.255.0 172.16.4.1 130

Sometimes static routes are used for backup purposes. A static route can be

configured on a router that will only be used when the dynamically learned route

has failed. To use a static route in this manner, simply set the administrative

distance higher than that of the dynamic routing protocol being used.


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Verifying Static

Route ConfigurationAfter static routes are configured it is important to verify

that they are present in the routing table and that routing

is working as expected.

The command show running-config is used to view the

active configuration in RAM to verify that the static route

was entered correctly.

The show ip route command is used to make sure that the

static route is present in the routing table.


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Trouble Shooting Static

Route Configuration


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Network and Host Addressing

Using the IP address of the

destination network, a router can

deliver a packet to the correct

network.

When the packet arrives at a router

connected to the destination

network, the router uses the IP

address to locate the particularcomputer connected to that

network.

Accordingly, every IP address has two

parts.


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IP Address Classes

IP addresses are divided into classes to define the large, medium,

and small networks.

Class A addresses are assigned to larger networks.

Class B addresses are used for medium-sized networks, &

Class C for small networks.


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Identifying Address Classes


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Address Class Prefixes

To accommodate different size networks and aid in classifying these networks, IP addressesare divided into groups called classes.This is classful addressing.


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Network and Host Division

Each complete 32-bit IP address is broken down into a network part and a

host part. A bit or bit sequence at the start of each address determines

the class of the address. There are 5 IP address classes.


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Class A Addresses

The Class A address was designed to support extremely large

networks, with more than 16 million host addresses available. Class A

IP addresses use only the first octet to indicate the network address.

The remaining three octets provide for host addresses.


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Class B Addresses

The Class B address was designed to support the needs of moderate

to large-sized networks.A Class B IP address uses the first two of the

four octets to indicate the network address. The other two octets

specify host addresses.


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Class C Addresses

The Class C address space is the most commonly used of the original

address classes.This address space was intended to support small

networks with a maximum of 254 hosts.


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IP Address Ranges

The graphic below shows the IP address range of the first octet both

in decimal and binary for each IP address class.


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Public IP Addresses

Unique addresses are required for each device on a network.

Originally, an organization known as the Internet Network Information Center

(InterNIC) handled this procedure.

InterNIC no longer exists and has been succeeded by the Internet AssignedNumbers Authority (IANA).

No two machines that connect to a public network can have the same IP address

because public IP addresses are global and standardized.

All machines connected to the Internet agree to conform to the system.

Public IP addresses must be obtained from an Internet service provider (ISP) or a

registry at some expense.


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Private IP Addresses

Private IP addresses are another solution to the problem of the impending

exhaustion of public IP addresses.As mentioned, public networks require

hosts to have unique IP addresses.

However, private networks that are not connected to the Internet may useany host addresses, as long as each host within the private network is

unique.


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APPLICATIONS:-

Applications:-

1.-High-Speed, Secure Internet Access

Businesses can take advantage of having a single, fast connectionto the

Internet that is shared by all users rather than having

individual separate telephone lines and modems for Internet

access.

2.- Telecommuting

Telecommuters can take advantage of advanced

servicessuch as secure Internet access and virtual private

networks (VPNs)that minimize telecommuting costs.


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ROUTER MANUFACTURING COMPANIES:-

1.CISCO

2.JUNIPER 3.ALCATEL

4.HUAWEI


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REFERENCES:-

Official website of CISCO

www.cisco.comwww.wikipedia.org

Date post:	08-Apr-2018
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Routers &Ip Addrrresing

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