Report on Router

FINAL REPORT ON ROUTER

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Contents
INTRODUCT ION: ................................................................................................. 2
How r outers wor k ................................................................................................. 7
Like a postal system or courier ........................................................................... 8
Routing Protocol ................................................................................................... 9
Types of routing protocol ...................................................................................... 9
Enhanced Interior Gat eway Routing Protocol (EIGRP) ........................................ 10
Interior Gateway Rout ing Protocol ( IGRP) ......................................................... 11
TYPES OF ROUTERS: ........................................................................................ 12
Broadband Routers: .......................................................................................... 12
Wireless Routers:............................................................................................. 13
OTHER TYPE ROUTERS: ................................................................................... 14
EDGE ROUTER: .............................................................................................. 14
SUBSCRIBER EDGE ROUTER: ........................................................................ 15
INTER-PROV IDER BORDERS ROUTER: .......................................................... 15
Core Router ..................................................................................................... 16
Advantage and Disadvantage of Routers ............................................................... 16
Advantage: ...................................................................................................... 16
Easily Shared Internet ...................................................................................... 16
Security and Adaptabi lity ................................................................................. 16
Disadvantage: .................................................................................................. 17
Complicated Setup ........................................................................................... 17
Data Overhead ................................................................................................. 17


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INTRODUCTION:
A router is a device that forwards data packets between computer network
creating an overlay internetwork. A router is connected to two or more data
lines from different networks. When a data packet comes in one of the lines, the
router reads the address information in the packet to determine its ultimate
destination. Then, using information in its routing table or routing policy, it
directs the packet to the nex t network on its journey. Routers perform the
"traffic directing" functions on the internet. A data packet is typicall y forwarded
from one router to another through the networks that constitute the internetwork
until it reaches its destination node.
The most familiar t ype of routers are home and small office routers that simpl y
pass data, such as web pages, email, IM, and videos between the home
computers

and

the

Internet.

An

example

of

a

router

would

be

the

owner's cable or DSL modem, which connects to the Internet through an ISP
More sophisticated routers, such as enterprise routers, connect large business or
ISP networks up to the powerful core routers that forward data at high speed
along the optical fiber lines of the internet background. Though routers are
typicall y dedicated hardware devices, use of software -based routers has grown
increasingl y common. Routers are very common today in every network area,
this is mainl y because every network these days connect to some other network,
whether it's the Int ernet or some other remote site. Routers get their name from
what they do.which is route data from one network to another. Routers capture
the information that come through broadband connection via a modem and
deliver it to your computer The router choose route for the packet so that you
receive the information Firstl y. Routers are multiport devices and more
sophisticated as compared to repeaters and bridges. Routers also support
filtering bridges. They operate at physical, data link a nd network layer of OS I
model.


3

Like bridges, they are self learning, as they can communicate their existence to
other devices and can learn of the existence of new routers, nodes and LAN
segments.
A router has access to the network layer address or logica l address (IP address).
It contains a routing table that enables it to make decisions about the route i.e.
to determine which of several possible paths between the source and destination
is the best for a particular transmission. These routing tables are d ynamic and
are updated using routing protocols.
The routers receive the packets from one connected network and pass them to a
second connected network. However, if a received packet contains the address
of a node that is on some other network (of which the router is not a member),
the router determines which of its connected networks the best next relay point
for that packet is. Once the router has identified the best route for a packet to
travel, it passes the packet along the appropriate network to anothe r router. That
router checks the destination address, find what it considers the best route for
the packet and passes it to the destination network .
Router is a network communication device that is used to connect logicall y and
physicall y different networks. It can be used in the Ethernet, FDDI, Token Ring,
ATM, Frame Relay, ISDN and other t ypes of the LAN/WAN. The router’s main
purpose is the sorting and distribution the data packets. Router contains and
maintains the routing table that has the in formation of the adjacent routers and
other connected networking devices. Router selects the shortest possible path to
send the data packets at the destination. It is an intelligent device that can
connect ATM with Frame Relay, ISDN with Frame Relay, SONET with ATM or
any other two dissimilar networks. Router uses different protocols such as RIP
(Routing Information Protocol), OSPF (Open Shortest Path First) and BGP and
IGRP (Interior Gateway Routing Protocol) and EIGRP (Enhanced Interior
Gateway Routing Pr otocol. Routing protocols specifies that how routers will
communicate with each other in the WAN.


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They determine that which path to select to send the data towards its
destination. There are three main t ypes of the routing protocols i.e. link state,
path vector and distance vector. Router contains the operating system, Flash
memory, NVRAM and processor.

High level routers contain the Application

Specific Integrated Circuits to perform parallel proce ssing. A router is also act
as

a

gateway

that

connects

LAN

with

the

inte rnet

For home and business users that use the high speed DSL connection a router
also act as a hardware firewall device. It filters and blocks the unwanted traffic
based on the IP address, port, protocol, application and service.

Before buying

router for deploying in your home or office network make sure it is compatible
with other devices in your networks. It is recommend that you buy and deploy
the all the network devices from the same vendor. Computers that specialize in
sending packets over the data networ k.They are responsible for interconnecting
networks by selecting the best path for a packet to travel and forwarding packets
to their destination Function of router is to take out the destination IP address
from the packet and determines the next network p oint to which a data packet
should be forwarded towards its destination. Before reaching the destination
from source, packet may have to follow a long path, in between it may go
through many routers, like first router m ay send it to second and so on number
may rise up to 10 to 20 routers .



Data is sent in form of packets between 2 end devices



Routers are used to direct packet to its destination

There are two major groups of router interfaces

LAN Interfaces:
1: Are used to connect router to LAN network
2: Has a layer 2 MAC address
3: Can be assigned a Layer 3 IP address
4: Usuall y consist of an RJ -45 jack

5


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 WAN Interfaces:
1: Are used to connect routers to external networks that interconnect LANs.
2: Depending on the WAN technology, a layer 2 address may be used.
3: Uses a layer 3 IP address

In such cases router can act as hardware firewall, it does not allow computer’s
IP address to directly expose to the internet A router work at layer 3 on OS I
Model and have functions on Layer 4 (filtering AC L, NAT) and don't perform
any scan on Hosts. Basicall y, He only route packets so onl y know the
source/destination IP and if the PC is on a subnet directl y connected he know
the MAC address. Some routers can capture packet or monitoring and by this
information you can determine Port of a Host. If you use overloaded an
encrypted VPN can prevent the reading of information of packets.


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How routers work
A router passes data between multiple networks. It works at the “layer 3” (the
network link layer),

which means that it must be able to understand the data packets so that it can
route them to their destination.
Routers are essentially computers optimized for handling p ackets that have
to be transferred between separate networks. Routers attempt to send
packets from their source to their destination in the fastest way possible,


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which is not always the absolute shortest path.
On a network, packets with destinations on th e LAN go directl y from the
sending machine to the destination machine without any intermediaries.
However, if the destination address of a packet is outside the LAN, the
sending machine sends it to the router, which the sending machine knows as
the default gateway, and has no further interaction with that packet.
When the router receives a packet destined for a point outside the LAN, it
looks to see if it has a route to get the packet to that destination network. If it
does (or if it has a default gateway of its own), it will send the packet to the
next stop.

Like a postal system or courier
Routing between a LAN and a wide -area network (WAN) is like a postal
s ystem or a courier network. A package traveling from New York to San
Francisco might travel through a hub in Memphis or Chicago and be re sorted in Reno before heading to its final destination. If the package had
to be hand-delivered quickl y, you could do that, but the cost would
increase significantly, and hopefull y, the package won't get routed the
long way around, because that tends to be inefficient and difficult to
trace.
In the same manner, routers send packets according to the available routes
between networks and try to determine the shortest possible route at any
given time.
How does a router do this? Well, inside a router is a set of data called
routing tables. Routing tables include:
•
•

All possible routes the router is aware of Information on which
connections lead to particular groups of addresses
Priorities for connections to be used Rules for handling both routine
and special cases of traffic

Routing tables are dynamic — they are updated by routing protocols
such as Routing Information Protocol (R IP) or Open Shortest Path First
(OSPF) that constantl y pass messages between routers. Th e router
consults them to determine whether or not it has a route to a particular
destination address.


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Routing Protocol
A routing protocol specifies
how routers communicate
with
each
other,
disseminating information that enables them to select routes between an y
two nodes on a computer network. Routing algorithms determine the specific
choice of route. Each router has a priori knowledge onl y of networks attached to
it directl y. A routing protocol shares this information first among immediate
neighbors, and then throughout the network. This way, routers gain knowledge
of the topology of the network.
Although there are many t ypes of routing protocols, three major classes are in
widespread use on IP networks:
Interior gateway routing via link state routing protocols , such as OSPF and ISIS
Interior gateway routing via distance
as R IPv2, IGRP and EIGRP

vector

routing

protocols,

such

Exterior gateway routing . The Border Gateway Protocol (BGP), a path vector
routing protocol , is the routin g protocol used on the Internet for exchanging
traffic between Autonomous S ystems .
Many routing protocols are defined in documents called RFCs
Some versions of the Open S ystem Interconnection (OS I) networking model
distinguish routing protocols in a special sub layer of the Network Layer (Layer
3).
The specific characteristi cs of routing protocols include the manner in which
they avoid routing loops, the manner in which they select preferred routes, using
information about hop costs, the time they require to reach routing convergence,
their scalabilit y, and other factors.

Types of routing protocol
Some of the most common routing protocols include IGRP, EIGRP, OSPF, IS -IS
and BGP. There are two primary routing protocol t ypes although many different
routing protocols defined with those two t ypes. Link state and distance vector
protocols comprise the primary t ypes. Distance vector protocols advertise their
routing table to all directl y connected neighbors at regular frequent intervals
using a lot of bandwidth and are slow to converge. When a route becomes
unavailable, all router tables must be updated with that new information. The
problem is with each route r having to advertise that new information to its
neighbors, it takes a long time for all routers to have a current accurate view of
the network. Distance vector protocols use fixed length subnet masks which


10

aren't scalable. Link state protocols advertise routing updates onl y when they
occur which uses bandwidth more effectivel y. Routers don't advertise the
routing table which makes convergence faster. The routing protocol will flood
the network with link state advertisements to all neighbor routers per are a in an
attempt to converge the network with new route information. The incremental
change is all that is advertised to all routers as a multicast LSA update. They
use variable length subnet masks, which are scalable and use addressing more
efficientl y.

Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced Interior Gateway Routing Protocol is a hybrid routing protocol
developed by Cisco systems for routing many protocols across an enterprise
Cisco network. It has characteristics of both distance v ector routing protocols
and link state routing protocols. It is proprietary which requires that you use
Cisco routers. EIGRP will route the same protocols that IGRP routes (IP, IPX,
use the same composite metrics as IGRP to select a best path destination. As
well there is the option to load balance traffic across equal or unequal metric
cost paths. Summarization is automatic at a network class address however it
can be configured to summarize at subnet boundaries as well. Redistribution
between IGRP and EIGRP is automatic as well. There is support for a hop count
of 255 and variable length subnet masks.

Convergence
Convergence with EIGRP is faster since it uses an algorithm called dual update
algorithm or DUAL, which is run when a router detects that a particular route is
unavailable. The router queries its neighbors looking for a feasible successor.
That is defined as a neighbor with a least cost route to a particular destination
that doesn't cause any routing loops. EIGRP will update its routing table with
the new route and the associated metric. Route changes are advertised onl y to
affected routers when changes occur. That utilizes bandwidth more efficientl y
than distance vector routing protocols.

Autonomous Systems
EIGRP does recognize assignment of different autonomous systems which are
processes running under the same administrative routing domain. Assigning
different autonomous system numbers isn't for defining a backbone such as with
OSPF. With IGRP and EIGRP it is used to change route redistribution, filtering
and summarization points.


11

Characteristics
Advanced Distance Vector
Routes IP, IPX
Routing Advertisements: Partial When Route Changes Occur
Metrics: Bandwidth, Delay, Reliabilit y, Load, MTU Size
Hop Count: 255
Variable Length Subnet Masks
Summarization on Network Class Address or Subnet Boundary
Load Balancing Across 6 Equal or Unequal Cost Paths (IOS 11.0)
Hello Timer: 5 seconds on Ethernet / 60 seconds on Non -Broadcast
Holddown Timer: 15 seconds on Ethern et / 180 seconds on Non -Broadcast
Metric Calculation = destination path minimum BW * delay (msec) * 256
Split Horizon

Interior Gateway Routing Protocol (IGRP)
Interior Gateway Routing Protocol is a distance vector routing protocol
developed by Cisco systems for routing multiple protocols across small and
medium sized Cisco networks. It is proprietary which requires that you use
Cisco routers. This contrasts with IP RIP and IPX RIP, which are designed for
multi-vendor networks. IGRP will route IP, IPX, Decnet and AppleTalk which
makes it very versatile for clients running many different protocols. It is
somewhat more scalable than RIP since it supports a hop count of 100, onl y
advertises every 90 seconds and uses a composite of five different metrics to
select a best path destination. Note that since IGRP advertises less frequentl y, it
uses less bandwidth than R IP but converges much slower since it is 90 seconds
before IGRP routers are aware of network topology changes. IGRP does
recognize assignment of different autonomous systems and automaticall y
summarizes at network class boundaries. As well there is the option to load
balance traffic across equal or unequal me tric cost paths.

Characteristics
Distance Vector
Routes IP, IPX, Decnet, Appletalk
Routing Table Advertisements Every 90 Seconds
Metric: Bandwidth, Delay, Reliabilit y, Load, MTU Size
Hop Count: 100
Fixed Length Subnet Masks
Summarization on Network Class Address
Load Balancing Across 6 Equal or Unequal Cost Paths ( IOS 11.0 )
Update Timer: 90 seconds


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Invalid Timer: 270 seconds
Holddown Timer: 280 seconds
Metric Calculation = destination path minimum BW * delay (usec)
Split Horizon

TYPES OF ROUTERS:
There are several t ypes of routers in the market.

Broadband Routers:
Broadband routers can do different t ypes of things. Broadband routers can be
used to connect computers or to connect to the Internet.
If you connect to the internet through phone and using Voice over IP technology
(VOIP) then you need broadband router. These are often a special t ype of
modem (ADSL) that will have both Ethernet and phone jacks.
A device that provides access to the Internet for multiple computers. It t ypicall y
includes a netwo rk switch with four or more Ethernet ports for wired
connections to desktop and laptop computers. "Wireless routers include a wifi
access point The device forwards Internet traffic from the computers to the
cable or DS L modem and switches non -Internet traf fic between the connected
machines. It combines a router, network switch and DHCP server (to assign IP
addresses to stations). The router also provides network address translation
(NAT), which allows multiple users to reach the Internet with one public IP
address assigned by the cable or telephone company to the service outers
capture the information that come through broadband connection via a modem
and deliver it to your computer The router choose route for the packet so that
you receive the information Firstl y. Routers are multiport devices and more
sophisticated as compared to repeaters and bridges.
A broadband router utilizes the Ethernet standard for wired connections.
Traditional broadband routers required Ethernet cables be run between the
router, the broadband modem, and each computer on the home network.


13

Wireless Routers:
Wireless routers create a wireless signal in your home or office. So,
any PC within range of Wireless routers can connect it and use your Internet.
In order to secure your Wireless routers, you simpl y need to come secure it with
password or get your IP address. Then, you'll log on into your router with the
user ID and passwords will that come with your router.A network device that
combines a router, switch and Wi -Fi access point (Wi -Fi base station) in one
box. Wireless routers provide a convenient way to connect a small number of
wired and any number of wireless computers to the Internet. For more about
wireless networks It is commonl y used to provide access to the Internet or a
computer network. It does not require a wired link, as the connection is made
wirelessl y, via radio waves.
A wireless router is a device that enables wireless network packet forwa rding
and routing, and serves as an access point in a local area network. It works
much like a wired router but replaces wires with wireless radio signals to
communicate within and to external network environments. It can function as a
switch and as an Int ernet router and access point A wireless router is the router
found in a wireless local area network (WLAN) for home and small office
networks. It enables Internet and local network access. Typicall y, the wireless
router is directl y connected to a wired or wireless WAN. Users connected to the
wireless router are able to access the LAN as well as the external WAN, such as
the Internet. Depending on the capabilities of the wireless router, it can support
from a few to hundreds of simultaneous users. Moreover, most wireless routers
can also function as a firewall with the abilit y to block, monitor, and control
and filter incoming and outgoing network traffic.


14

It enables you to run a computer or gaming system from anywhere in the house
without having to ru n cables through the walls.

OTHER TYPE ROUTERS:
EDGE ROUTER:
A router is a device that forwards data packets between computer networks,
creating an overlay internetwork. A router is connected to two or more data
lines from different networks. When a data packet comes in one of the lines, the
router reads the address information in the packet to determine its ultimate
destination. Then, using information in its routing table or routing policy, it
directs the packet to the next network on its journey. Router s perform the
"traffic directing" functions on the Internet. A data packet is t ypicall y
forwarded from one router to another through the networks that constitute the
internetwork until it reaches its destination node


15

The most familiar t ype of routers are home and small office routers that simpl y
pass data, such as web pages, email, IM, and videos between the home
computers

and

the

Internet.

An

example

of

a

router

would

be

the

owner's cable or DSL modem which connects to the Internet through an ISP.
More sophisticated routers, such as enterprise routers, connect large business or
ISP networks up to the powerful core routers that forward data at high speed
along the optical fiber lines of the Internet backbone. Though routers are
typicall y dedicated hardware devices, use of software -based routers has grown
increasingl y common.
This t ype of router are placed at the edge of the ISP network, they are normall y
configured to external protocol like BGP (Border gateway protocol) to another
BGP of other ISP or large o rganization.

SUBSCRIBER EDGE ROUTER:
This t ype of router belongs to an end user (enterprise) organization. It’s
configured to broadcast external BGP to its provider’s .

INTER-PROVIDER BORDERS ROUTER:
This t ype of router is for Interconnecting ISPs, this is a BGP speaking router
that maintains BGP sessions with other BGP speaking routers in other providers .


16

Core Router
A router that resides within the middle or backbone of the LAN network rather
than at its periphery. In some instances, a core router provides a step down back
bone, interconnecting the distribution routers from multiple building of a
campus (LAN), or Large enterprise Location (WAN). They tend to be optimized
for a high bandwidth. A core router is a router that forwards packets to
computer hosts within a network but not between networks). A core router is
sometimes contrasted with an edge router, which routes packets between self contained network and other outside networks along a network backbone.

Advantage and Disadvantage of Routers

Advantage:

Easily Shared Internet
One of the biggest reasons for using a router is to connect multiple users to the
Internet. Connecting to the Internet requires a publicl y -unique IP address. As
such, Internet provi ders t ypicall y onl y offer a single IP address or charge fees
for large amounts of publicl y routable addresses. The solution is to add a router
with network address translation enabled. Connecting to the Internet through a
router with NAT allows the router to use the single public IP address and a
series of UDP ports to share the connection. Without NAT, connecting a large
organization’s computers to the Internet becomes virtuall y impossible .

Security and Adaptability
Connecting an Internet modem directl y to a PC exposes that PC to a host of
securit y issues. Furthermore, expanding a direct -connection network becomes
complicated without the addition of switches or a router and communicating
between the individual PCs becomes difficult. Using a router as an i ntermediary
between the “outside” network of the Internet and the “inside” network of your


17

organization provides a scalable environment that is also, to a degree, easier to
secure. A router is not a replacement for a firewall or anti -malware measures,
but it’s an important first step towards a largel y secure network environment.

Disadvantage:

Complicated Setup
The aforementioned router requires NAT to be set up. In addition, each
computer must be assigned a private IP address that is t ypically organized by a
DHCP server. This is required for the simplest connections. Connecting to
additional IP -based networks adds additional complication in the form of
routing tables -- a table that describes the best route for reaching a desired
network. If IP telephony or video services are to be running on the IP network,
you’ll also need to consider qualit y of service configu rations. helps prioritize
one t ype of traffic, such as voice, over others when bandwidth is limited. As
additional services are added, more configuration becomes required of the router

Data Overhead
Unlike a point-to-point “layer 2” link, routers add addit ional IP -based headers.
These headers include information such as source and destination addresses,
UDP information and checksums. These headers are attached to every payload of
data. Large pieces of data are t ypically broken into thousands of smaller
headers, making this header data consume a percentage of the total available
bandwidth.

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