This document provides an overview of local area networks (LANs) and virtual LANs (VLANs). It defines LAN as a network covering a small area like a home, office or campus to connect computers in close proximity. The document discusses common LAN topologies like bus, ring and star. It then introduces VLAN as a way to logically segment devices within a LAN even if they share the same infrastructure. The document explains how VLANs work using tags and trunking between switches. It outlines benefits of VLANs like improved security, flexibility and traffic management compared to traditional LANs.

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1
LAN & VLAN
Presented By:-
RAMAKANT TYAGI

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BASIC OF NETWORKING
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• There are 7 layer in
networking
• Out Of the 7 layers, we
are concerned with the
bottom 3 layers.
• The top 4 layers are used
more on host machines
to support TCP/UDP,
HTTP, other
applications
Application Layer (Layer
7)
Presentation Layer
(Layer 6)
Session Layer (Layer 5)
Transport Layer (Layer
4)
Network Layer (Layer 3)
Data Link Layer (Layer
2)
Physical Layer (Layer 1)

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Network Devices
• There are 5 general devices:
Repeater
Hub
Bridge
Switch
Router
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Repeater
A Layer 1 device
An electronic device to receive a signal
on a port and retransmits it at a higher
level or higher power
Used when you need to go farther
distances than the cabling will allow
Usually has 2 ports (IN/OUT)
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Hub
A Layer 1 device
A device that contains multiple ports
Has no logic or “brain”
Simply passes data out all other ports
In simple terms, it is a multi-port repeater
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Bridge
A Layer 2 device
Connects multiple Layer 2 segments
Has logic or “brain”
Learns what Layer 2 MAC addresses are
associated with each port
Receives frames destined for a particular
MAC address and only sends the data out
the correct port
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Switch
A layer 2 device
Basically a multi-port bridge
Learns MAC Addresses to Port
mappings
Doesn’t flood data out every port unless
the MAC address hasn’t been learned
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Router
A Layer 3 device
Connects multiple Layer 3 networks
Uses Layer 3 addressing (IP addressing)
Allows communication between
different Layer 2 segments
Breaks up broadcast domains
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Introduction
• Definition: A local area network
(LAN) supplies networking capability to a
group of computers in close proximity to
each other such as in an office building, a
school, or a home. A LAN is useful for
sharing resources like files, printers, games
or other applications. A LAN in turn often
connects to other LANs, and to the Internet
or other WAN.
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Diagrammatic representation
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Local Area Network (LAN)
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LAN OVERVIEW
• A LAN is a computer network that covers a small area (home,
office, building, campus)
– a few kilometers
• LANs have higher data rates (10Mbps to 40Gbps) as compared to
WANs
• LANs (usually) do not involve leased lines; cabling and
equipments belong to the LAN owner
• A LAN consists of
– Shared transmission medium
• now so valid today due to switched LANs (for wired LANs),
but still valid for wireless LANs
– regulations for orderly access to the medium
– set of hardware and software for the interfacing devices
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LAN Topologies
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Bus Topology
• Stations attach to linear medium
(bus)
– Via a tap - allows for transmission
and reception
• Transmission propagates in
medium in both directions
• Received by all other stations
– Not addressed stations ignore
• Need to identify target station
– Each station has unique address
– Destination address included in
frame header
• Terminator absorbs frames at the
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Bus Topology
• Need to regulate transmission
– To avoid collisions
• If two stations attempt to transmit at same time,
signals will overlap and become garbage
– To avoid continuous transmission from a single
station. If one station transmits continuously, access is
blocked for others
• Solution: Transmit Data in small blocks – frames
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Ring Topology
• Repeaters joined by point-to-point links in closed
loop
– Links are unidirectional
– Receive data on one link and retransmit on another
– Stations attach to repeaters
• Data transmitted in frames
– Frame passes all stations in a circular manner
– Destination recognizes address and copies frame
– Frame circulates back to source where it is removed
• Medium access control is needed to determine
when station can insert frame
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Ring Topology
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Star Topology
• Each station connected
directly to central node
– using a full-duplex
(bi-directional) link
• Central node can broadcast (hub)
– Physical star, but logically like bus due
to broadcast medium
– Only one station can transmit at a time;
otherwise, collision occurs
• Central node can act as frame switch
– retransmits only to destination
– today’s technology
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Summary Of Network Topology
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Topology/structure Advantages Disadvantages
Bus structure -easy to install
-simply expandable
-short cable lengths
-net expansion limits
-complicated access
methods
Ring structure -large net expansion -complex error tracing
-high wiring expenditure
-when disturbances net
failure
Star structure -simple cross-linking
-simple extension
-high reliability
-high wiring expenditure
-net failure in case of
failure or overloading of
the hubs

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ADVANTAGES OF LAN
• Expensive hardware can be shared e.g. laser
printer.
• Users can access the same files.
• Messages can be sent between users.
• A single Internet connection can be shared
among many users.
• Network software is cheaper than buying
individual packages.
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DISADVANTAGES OF LAN
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 Disadvantages of connecting computers in a LAN:
• Special security measures are needed to stop users from using
programs and data that they should not have access to.
• Networks are difficult to set up and need to be maintained by skilled
technicians.
• If the file server develops a serious fault, all the users are affected,
rather than just one user in the case of a stand-alone machine.
• Wired and therefore more difficult to setup. Drilling holes in wall,
running cables in lofts etc, fitting sockets and redecorating. More
expensive to set up. More time consuming to set up. Not as flexible,
can only use where there is a socket - cannot use outside for example.
• Wired systems cannot be used in listed buildings

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VLAN Introduction
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Introduction
 In simple terms, a VLAN is a set of workstations
within a LAN that can communicate with each
other as though they were on a single, isolated
LAN.
 What does it mean to say that they “communicate
with each other as though they were on a single,
isolated LAN”?
 Among other things, it means that:
 broadcast packets sent by one of the workstations
will reach all the others in the VLAN
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Introduction
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 Broadcasts sent by one of the workstations in the VLAN
will never reach any workstations that are not in the
VLAN
 The workstations can all communicate with each other
without needing to go through a gateway. For example, IP
connections would be established by AR Ping for the
destination
 IP and sending packets directly to the destination
workstation—there would be no need to send packets to the
IP gateway to be forwarded on.
 The workstations can communicate with each other using
non-routable protocols

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VLAN-based LAN
• As we earlier
discussed ,By
utilizing VLANs, the
same users can be
spread out over
various geographical
locations and still
remain in their same
IP subnet (broadcast
domain).
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VLAN OVERVIEW
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• A VLAN allows a network administrator to create groups
of logically networked devices that act as if they are on
their own independent network, even if they share a
common infrastructure with other VLANs.
• Using VLANs, you can logically segment switched
networks based on functions, departments, or project
teams.
• You can also use a VLAN to geographically structure your
network to support the growing reliance of companies on
home-based workers.
• These VLANs allow the network administrator to
implement access and security policies to particular groups
of users.

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OVERVIEW
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HOW VLAN WORKS ?
• VLANs are identified by a number
– Valid ranges 1-4094
• On a VLAN-capable switch, you assign ports
with the appropriate VLAN number
• The switch then only allows data to be sent
between ports with the same VLAN
• Since almost every network is larger than a single
switch, there needs to be a way to have traffic
sent between two different switches
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HOW VLAN WORKS ?
• One way to do it is to assign a port on each switch with a
VLAN and run a cable between the switches
– Not very feasible or cost effective
• For example, if there were 6 hosts on each switch on 6
different vlans, you would need 6 ports on each switch
to connect the switches together. This would mean
that if you had 24 different vlans you could only have
24 hosts on a 48 port switch
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HOW VLAN WORKS ?
• There was a standard develop to make it so that a
single connection between two switches could be
used to send traffic for all vlans
• 802.1q – Provides a VLAN tag in front of the
Layer 2 frame
• We enable 802.1q tagging (trunking) on the ports
between the switches
• The switch receives the frame with the 802.1q header and
strips it off & It determines what VLAN and sends the
data to the appropriate port
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Types of VLAN
• Three basic VLAN memberships for
determining and controlling how a packet
entering a switch gets assigned to a VLAN.
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Port driven VLANs
• Most common configuration method
• User assigned by port association
• Easily administered through GUIs
• Maximizes security between VLANs
• Packets do not “leak” into other domains
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Port driven VLANs cont’d.
• User assigned port association ???
• For example, in a bridge with four ports, ports 1, 2, and 4
belong to VLAN 1 and port 3 belongs to VLAN 2
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Port VLAN
1 1
2 1
3 2
4 1
Assignment of ports to different VLAN's.
Disadvantage:
•Does not allow for user mobility

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MAC address driven VLANs
• User assigned based on MAC addresses
• Offers flexibility
• For Example:Since MAC addresses form a part
of the workstation's network interface card, when a
workstation is moved, no reconfiguration is needed to
allow the workstation to remain in the same VLAN
• Impacts performance, scability, and administration
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MAC address driven VLANs cont’d
• Disadvantage
• VLAN membership must be assigned initially.
• In networks with thousands of users. Also, in environments
where notebook PC's are used, the MAC address is associated
with the docking station and not with the notebook PC.
Consequently, when a notebook PC is moved to a different
docking station, its VLAN membership must be reconfigured.
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MAC Address VLAN
1212354145121 1
2389234873743 2
3045834758445 2
5483579475843 1
Assignment of IP subnet addresses to different VLAN's

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Network address driven VLANs
• The network IP subnet address can be used to
classify VLAN membership
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IP Subnet VLAN
23.2.24 1
26.21.35 2
Assignment of IP subnet addresses to different VLAN's

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Network address driven VLANs
cont’d
• IP addresses are used only as a mapping to
determine membership in VLAN's.
• In Layer 3 VLAN's, users can move their
workstations without reconfiguring their network
addresses. The only problem is that it generally
takes longer to forward packets using Layer 3
information than using MAC addresses.
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Benefits of VLAN
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Benefits of VLAN
• VLANs allow network administrators to organize LANs logically
instead of physically.
• Easily move workstations on the LAN
• Easily add workstations to the LAN
• Easily change the LAN configuration
• Easily control network traffic
• Improve security
VLAN can also be used to control broadcast domains
Set up firewalls
Restrict access
Inform the network manager of an intrusion
• Eliminate the need for expensive routers
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Disadvantages Of Vlan
*Management is complex
*Possible problems in interoperability
*A VLAN cannot forward traffic to another
VLAN(need a router to communicate
between VLANs)
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LAN V/S VLAN
• VLAN requires lesser cost by eliminating use of
expensive routers unlike LAN.
• Data transmission is safe on VLAN as compared
to LAN.
• VLAN delivers better performance when
compared to traditional LANs.
• VLAN also helps in reducing traffic
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Thank You