Routing Principles and ROUTER BASICS APT

7/28/2019 Routing Principles and ROUTER BASICS APT

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Routing Principles andRouter basicsCH SRINIVASA RAO

SDE (BB&NW)[email protected]

9440911911
mailto:[email protected]:[email protected]


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Router fundamentsThe router is a device that connects two networks

IT comes from the word ROUTEA router accepts packets on at least two network

interfaces and forwards packets from one interfaceto another.

A router works at network layer.

Each router maintains a database called routingtable of the router

This routing table contains network addresses.Routers do not talk to remote computers


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Functions of routers

Inter network communications

Best path selection

Packet switching

Packet forwarding


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Router fundamentalsRouter is like a PC and has

Mother boardCPU

Memory

Ports & interfaces to hook peripherals

May have a monitor to serve as a console

Types of routers

Hardware routersCisco, juniper, nortel , dlink, DAX

Software routersMicrosoft server , LINUX server


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CISCOs HIERARCHICAL DESIGN MODEL

Access Layer : Small organization

Ex:1600,1700,1800,2500 seriesDistribution Layer: Medium size organization

ex: 2600,2800,3600,3700,3800

Core layer : Very large organizations and ISPs.

ex:7200,7600,10000,12000


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Cisco Router Memories

Memory Type Contents

RAM 1. Active program & operating systeminstructions

2. Running configuration files3. Routing tables

NVRAM 1. Startup configuration files

ROM 1. POST (Power-On-Self-Test)

2. Startup/Power-up utilities

3. Limited version of IOS

Flash 1. IOS


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Interfaces of routersLAN Interface to connect to the switch

WAN Interface to connect to the next router(serial port)

Administrative port (console port)

Auxiliary port


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Accessing the Router CLI

User Mode

Interfaces

Console

Aux

Modem

Telnet


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Console connectivityConnect a rollover cable to the console port of the

router(RJ-45 connector)Attach the DB9 to the COM port of the computer

Open the emulation software

For windows: start Programs AccessoriescommunicationsHyperterminal

Give the name

In port settingsclick on restore defaults

LINUX:

#minicom -s


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Conditions for routing1.The IP address of LAN interface of router

should belong to the same network of LAN.2. The serial IPs of directly connectedrouters must belong to the same network.

3. The IP address in the LAN of everybranch must belong to different networks.

4. ALL interfaces of routers should be in

different networks.


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Route Table UpdationRoute table acquires information in two

ways:Manually

Static route entries

AutomaticallyDynamic routing protocols


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Static RoutingRoutes for each destination network has to

be manually configured by theadministrator.

Used in small networks.

Route may be up or down but static routeswill remain in the routing tables and trafficwould still be sent towards the route

Not suitable for large networksAdministrative distance for static route is 1


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Dynamic RoutingChanges in the network topology are updated

dynamically.Only the directly connected networksinformation is required for configuration.

Administrative work is reduced.

It is used in medium and large networks.

RIP & OSPF are routing protocols


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Hop Count

A hop count metric simply count router hops.

From router-A it is 1 hop to network192.168.5.0 if packets are sent out interface

192.168.3.0 and 2 hops if sent out 192.168.1.0

A B

C

192.168.1.0 192.168.7.0

192.168.6.0

192.168.5.0

192.168.2.0

192.168.3.0

192.168.4.0


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Bandwidth

A bandwidth metric would choose a higherbandwidth over a lower bandwidth.

A packet from router A to C will follow path

A-B-C. A B

C

192.168.1.0192.168.7.0

192.168.6.0

192.168.5.0

192.168.2.0

192.168.3.0

192.168.4.0

A-C: 64kbpsA-B: 2mbpsB-C: 2mbps


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Administrative DistancesDiversity of metrics poses problems in

routers running more than one routingprotocol.

Router may learn a route to the same

destination from each of the protocolsAdministrative distances are the routesources to determine most preferred source


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Administrative DistancesThe administrative distance of various

protocols is as below:Connected Interface - 0Static Route - 1

EIGRP - 90

OSPF - 110

RIP - 120

External EIGRP - 170

Unknown - 255The lower the administrative distance, themore believable the protocol.


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IOS MODES1. User Mode:Router>

Router is the default host name and can be changed, '>' symbol implies"user mode".This is the first mode user interacts with the IOS. It is a restrictedmode and support only a very few basic commands.2. Privilege Mode:

Router#

'#' symbol implies "Privilage Mode". This mode has full administrativerights.this mode is generally used for advanced troubleshooting using'show' and 'debug' command. This is also called the EXEC mode.3. Global Configuration mode:Router (config)#'(config)# ' symbol implies "global configuration mode". Configuration

of the router starts from this mode configurations that affect thecomplete router are given. Example, host name of the router.


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IOS MODES4. interface configuration mode:

Router(config-if)#

'(config-if)# symbol implies "interface configuration mode".This mode is used to configure a specific interface.

5. Line configuration mode:

Router(config-line)#

'(config-line)# symbol implies "Line configuration mode".This mode is used to configure telnet, console and auxiliarymode.

6. Router Mode:

Router(config-router)#'(config-router)#'symbol implies "Router mode". This modeis used to configure different dynamic routing protocol.


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INITIAL CONFIGURATION


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INITIAL CONFIGURATIONDELHIRouter> (User Mode)Router>enableRouter# (Privilege Mode)Router# configure terminalRouter(config)# (Global Configuration Mode)Router(config)# hostname DELHIDELHI(config)# interface ethernet 0/0DELHI(config-if)# (Interface Configuration Mode)DELHI(config-if)# ip address 192.168.3.17 255.255.255.240DELHI(config-if)# no shutdown

DELHI(config-if)# exitDELHI(config)# line vty 0 4DELHI(config-line)# (Line Configuration Mode)DELHI(config-line)# password ciscoDELHI(config-line)# loginDELHI(config-line)# exitDELHI(config)# line con 0DELHI(config-line)# password ciscoDELHI(config-line)# loginDELHI(config-line)# exitDELHI(config)# enable password ciscoDELHI(config)# exit


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INITIAL CONFIGURATIONDELHI#configure terminal

DELHI(config)#interface serial 0/0

DELHI(config-if)#ip address 192.168.3.81 255.255.255.252

DELHI(config-if)# no shutdown

DELHI(config-if)# exit

DELHI(config)# interface serial 0/1DELHI(config-if)#ip address 192.168.3.93 255.255.255.252

DELHI(config-if)# no shutdown

DELHI(config-if)# exit


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Routing Principles and ROUTER BASICS APT

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