1. 2 Router is a device which makes communication between two or more networks present in different geographical locations. Routers are data forwarding.

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• Router is a device which makes communication between two

or more networks present in different geographical locations.

• Routers are data forwarding devices which work at layer 3

• Routers forward data based on logical addresses

(IP,IPX,Appletalk)

What is a Router ?

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Many companies are manufacturing Router :

• Cisco

• Nortel

• Multicom

• Cyclades

• Juniper

• Dlink

• Linksys

• 3Com

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Cisco defined the Router into 3 Layers

• Access Layer Router

• Distribution Layer Router

• Core Layer Router

Cisco’s Hierarchical Design Model

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Cisco 1700 Cisco 1760Cisco 800

• Routers which are used by Small Organizations

• Used for end user connectivity

• Router Series : 800, 1600, 1700, 2500,2600

Access Layer Router

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• Routers which are used by the ISPs

• Used for policy based routing and access control

Router Series : 2600, 3200, 3600, 3700

Distribution Layer Router

Cisco 2600XM/2691

Cisco 3700Cisco 3600

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• Routers which are used by the Global ISPs

• Used for fastest switching across internet

Router Series : 6400, 7200, 7300, 7400, 7500, 7600,

10000, 12000

Core Layer Router

Cisco 7000

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Modular Router

Difference between Modular Router & Fixed Router

Fixed Router are just like a brand PC where modification of interface is not possible.

Access layer router are the example of fixed router except 1600 and 1700 series

• Modular routers are just like assembled pc where modification of interface are possible.

• Distrubution and core layer routers are example of modular routers.

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Cisco 2501

Serial PortsS0 and S1

AUIAttachment Unit Interface

E0

Console(Con) 0

Auxiliary(Aux) 0

Power on/off Switch

Power Supply

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• It is used for connecting LAN to the Router.

• It is known as Ethernet Port or LAN port .

• AUI has 15 pin female connector (DB-15).

• Transceiver is used to connect RJ 45 to DB-15.

Attachment Unit Interface

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Transceiver

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E0 192.168.1.150/24

LAN - 192.168.1.0/24

1.1 1.2 1.3

An IP address is to be assigned to this interface and it should be in the same network as of the LAN.

An IP address is to be assigned to this interface and it should be in the same network as of the LAN.

Attachment Unit Interface

Straight Cable

Straight Cable

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E0 192.168.1.150/24

Attachment Unit Interface

Cross Cable Cross Cable is used to connect AUI of the router to PC-NIC

Cross Cable is used to connect AUI of the router to PC-NIC

LAN - 192.168.1.0/24

1.1

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1 2 3 4 5 6 7 8

12345678

12345678

Crimping of Twisted pair Cable

• Straight cable

Used between unlike devices e.g. Hub to PC, Switch to

PC, Hub to Router (AUI)

1 2 3 4 5 6 7 81 2 3 4 5 6 7 8

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Crimping of Twisted pair Cable

• Cross cable

Used between like devices E.g. : Hub to HUB, PC to

PC, Switch to Switch, HUB to Switch, PC to Router.

1 2 3 4 5 6 7 8

12345678

12345678

1 2 3 4 5 6 7 8

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Crimping of Twisted pair Cable

• Rollover Cable

Used for connecting Router Console Port to PC Com Port or

Serial port.

1 2 3 4 5 6 7 8

12345678

12345678

1 2 3 4 5 6 7 8

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• Serial interface has DB60 connector (60 pins)

in fixed routers

• Smart Serial interface has DB26 connector in modular

routers.

• It is known as WAN Port.

• It is used for connecting Remote Locations using V.35 cable,

which has 60 pins (male connector) at one end and 18 pins

(male connector) on the other end.

Serial Port

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V.35 Cable

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EXCHANGE

E0 192.168.1.150

LAN - 192.168.1.0/24

HYDERABAD OFFICE

E0 192.168.2.150

LAN - 192.168.2.0/24

CHENNAIMUX

2 pair of Copper Wire

G.703 Modem

G.703Modem

HYDERABADMUX

CHENNAI OFFICE

Fiber Optic Cable

V.35 Cable

V.35 Cable

V.35 Modem

S 0 S 1

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• It is known as Local Administrative Port

• It is used for Initial Configuration

• Password Recovery

• It is RJ 45 port

Console Port

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Console Connectivity

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Console Connectivity

• Connect one end of the rollover cable to the router’s console port (RJ-45 connector) and the other end of the cable to DB-9 converter

• Attach the female DB-9 converter to a PC Serial Port.

• Open Hyper Terminal (when using a windows operating system)

• Open minicom -s (when using a Linux operating system)

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DB9 Converter

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• It is known as Remote Administrative Port

• Used for remote administration

Auxiliary Port

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Auxiliary Connectivity

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• BRI Port

Basic Rate Interface used to connect ISDN.

It is available on 2503 and 2520 model routers

• 10 Base T Port

Used for connecting LAN to the Router. It is available on

2520 model router.

Other Ports

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2601 Model Router

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• WAN interfaces– Serial interfaces (S0, S1)– ISDN interface (BRI0)

• LAN interfaces - Ethernet– AUI (Attachment Unit Interface) (E0)– 10base T

• Administration interfaces– Console port – Auxiliary port

Brief Overview

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Internal Components

Router Internal Components

• The main internal components of the router are random-access memory (RAM), nonvolatile random-access memory (NVRAM), flash memory, read-only memory (ROM), and interfaces.

Router Internal Components

RAM is used for routing table information and it holds the running configuration.

NVRAM is used to store the backup/startup configuration file. Flash memory is

used for storage of full Cisco IOS software images.

ROM is used for permanently storing startup diagnostic code.

The console port provides physical access for initial configuration.

The interfaces provide LAN and WAN connectivity.

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Boot sequence

POST

ROM

FLASH

NVRAM

RAM

Power on Self Test (verifies the hardware)

Power on Self Test (verifies the hardware)

Loads the Bootstrap Program& Search where IOS is located

Loads the Bootstrap Program& Search where IOS is located

IOS is found in FlashIOS is found in Flash

Ios searches the NVRAM For startup Configuration File

Ios searches the NVRAM For startup Configuration File

NVRAM configuration is copied into the RAM

NVRAM configuration is copied into the RAM

Routers

• Routers are mainly used as WAN devices. • Routers use WAN connections to communicate

with each other. • Routers are the backbone devices of large

intranets and of the Internet. • They operate at Layer 3 of the OSI model, making

decisions based on network addresses.

Functions of a Router

• The two main functions of a router are to select the best path for packets and to route packets to the proper interface.

• Routers build routing tables and exchange network information with other routers.

• Routers segment local area networks

Functions of a Router Initiated by Router Configuration Files

•Selection of BEST PATH for data

•Controlling the flow of traffic in and out of the router (switching packets to appropriate interface)

•Specifying the correct set up and use of routed and routing protocols

Routers do this by building a routing table and sharing that information with other routers.

Difference between Routed Protocols and Routing Protocols

• Routing protocol would be OSPF, RIP, EIGRP, or BGP. These are protocols that distribute routing information, throughout all routers, on a network. By each router knowing about the networks that all others routers have connected, each router can determine the best path to take to delivery your traffic. Those are Routing protocols.

• Routed protocols are protocols that can be sent over a routed network. Today, with IP (think of TCP/IP) being the predominate protocol in use on the Internet and in most networks, we don't often think about routed vs unrouted protocols. That is because IP is a routed protocol. Meaning, IP is designed such that it can be routed over and through different networks. This is because the IP address is broken up into network and node (host) by the subnet mask. An example of a protocol that is not routed (unroutable) would be NETBIOS. It works great on a small local network (in your house) but wouldn't work well over a large network connected by dedicated network circuits or the Internet