seminaar ppt

8/7/2019 seminaar ppt

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Submitted To :

Mr. Vipin Nagar

Submitted By:

Anil Singh Banafer


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General introduction to mac address

y In a local area network (LAN) or other network, the MAC(Media Access Control) address is your computer's uniquehardware number. (On anEthernet LAN, it's the same as yourEthernet address.) When you're connected to the Internet

from your computer (or host as the Internet protocol thinksof it), a correspondence table relates your IP address to yourcomputer's physical (MAC) address on the LAN.

y The MAC address is used by the Media Access Control

sublayer of the Data-Link Layer (DLC) oftelecommunication protocols. There is a different MACsublayer for each physical device type. The other sublayerlevel in the DLC layer is the Logical Link Control sublayer.

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y A MAC address is an address which exists on Layer 2 of

the OSI Model.

y Layer 2 of the OSI model is theData Link Layer. The Data

Link Layer consists of two sublayers, the Media AccessControl (MAC) layer and the Logical Link Control (LLC)

layer. The MAC sublayer controls how a network node gains

access to the data and permission to transmit it.

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What is Mac Address????

y The MAC address is a unique value associated with a

networkadapter. MAC addresses are also known

as hardware addresses or physical addresses. They

uniquely identify an adapter on a LAN.

y MAC addresses are 12-digit hexadecimal numbers (48 bits in

length). By convention, MAC addresses are usually written in

one of the following two formats:

y

MM:MM:MM:SS:SS:SS

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y MAC addresses are globally unique addressed that are written into

hardware at the time of manufacture. For this reason, MAC

addresses are sometimes calledBurned In Addresses (BIA)

.y After manufacture, it is possible in many cases to change the MAC

address of a device in software.

y MAC addresses are used by many different Layer 2 technologies,

including Ethernet,Token Ring, 802.11,Bluetooth,

FDDI,ATM, SCSI, and Fibre Channel.

y Because MAC addresses originated in the Ethernet specification,

the MAC address is sometimes referred to as the Ethernet Address.

y A MAC address is 48 bits long. This means that there are281,474,976,710,656 possible MAC addresses.

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y MM-MM-MM-SS-SS-SS

y The first half of a MAC address contains the ID number of

the adapter manufacturer. These IDs are regulated by anInternet standards body . The second half of a MAC address

represents the serial number assigned to the adapter by the

manufacturer. In the example,

y 00:A0:C9:14:C8:29y The prefix

y 00A0C9

y indicates the manufacturer is Intel Corporation

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Why Mac Address?????

y Recall that TCP/IP and other mainstream networking

architectures generally adopt the OSI model. In this model,

network functionality is subdivided into layers. MAC

addresses function at the data link layer (layer 2 in the OSI

model). They allow computers to uniquely identify

themselves on a network at this relatively low level.

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Mac v/s IP Addressy Whereas MAC addressing works at the data link layer, IP addressing

functions at the network layer (layer 3). It's a slight oversimplification,but one can think ofIP addressing as supporting the softwareimplementation and MAC addresses as supporting the hardwareimplementation of the network stack. The MAC address generally

remains fixed and follows the network device, but the IP addresschanges as the network device moves from one network to another.

y IP networks maintain a mapping between the IP address of a device andits MAC address. This mapping is known as the ARP cache or ARPtable. ARP, the Address Resolution Protocol, supports the logic for

obtaining this mapping and keeping the cache up to date.y DHCP also usually relies on MAC addresses to manage the unique

assignment ofIP addresses to devices.

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Finding MAC Address.

y The method used to find a MAC address depends on the

type of network device involved. All popular networkoperating systems contain utility programs that allow us to

find (and sometimes change) MAC address settings.

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In Windows..y In Windows 95, Windows 98 and Windows ME,

the winipcfg utility displays the computer's MAC address. Usethe ipconfig utility (with the /all option) in Windows NT and anynewer versions of Windows.

y

Both 'winipcfg' and 'ipconfig' may display multiple MAC addressesfor one computer. One MAC address exists for each installednetwork card. Additionally, Windows maintains one or more MACaddresses that are not associated with hardware cards.

y For example, Windows dial-up networking uses virtual MAC

addresses to manage the phone connection as if it were a networkcard. Some WindowsVPN clients likewise have their own MACaddress. The MAC addresses of these "virtual" network adaptersare the same length and format as true hardware addresses.

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In Unix or Linux

y The specific command used in Unix to find a MAC address

varies depending on the version of the operating system. In

Linux and in some forms of Unix, the command "ifconfig -a"

returns MAC addresses.

y We can also find MAC addresses in Unix and Linux in the

boot message sequence. These operating systems display the

computer's MAC address on-screen as the system reboots.

Additionally, boot-up messages are retained in a log file

(usually "/var/log/messages" or "/var/adm/messages").

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In Macintosh

y We can find MAC addresses on the Macintosh in the TCP/IP

Control Panel. If the system is running Open Transport,

the MAC address appears under the "Info" or "User

Mode/Advanced" screens. If the system is running MacTCP,

the MAC address appears under the "Ethernet" icon.

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Summary of finding MAC Address

y Windows 95 and newer: winipcfg

y Windows NT and newer: ipconfig /all

y Linux and some Unix: ifconfig -a

y Macintosh with Open Transport: TCP/IP Control Panel -Info or User Mode/Advanced

y Macintosh with MacTCP: TCP/IP Control Panel - Ethernet

icon

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Need for changing MAC Address

y MAC addresses were designed to be fixed numbers that

cannot be changed. However, there are several valid reasons

to want to change your MAC address

y

Some of them are as follows:1)- Enable them to work with ISP.

2)-To be of use in cable modems.

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Enable them to work with ISP.y Most Internet subscriptions allow the customer only a single IP

address. The Internet Service Provider (ISP) may assign one static

(fixed) IP address to each customer. However, this approach is an

inefficient use ofIP addresses that are currently in short supply.

The ISP more commonly issues each customer dynamic IP addressthat may change each time the customer connects to the Internet.

y ISPs ensure each customer receives only one dynamic address

using several methods. Dial-up and many DSL services typically

require the customer to log in with a username and password.Cable modem services, on the other hand, do this by registering

and tracking the MAC address of the device that connects to the

ISP.

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y The device whose MAC address is monitored by an ISP can

be either the cable modem, a broadband router, or the PC

that hosts theInternet connection. The customer is free to

build a network behind this equipment, but the ISP expects

the MAC address to match the registered value at all times.

y Whenever a customer replaces that device, however, or

changes the network adapter inside it, the MAC address ofthis new equipment will no longer match the one registered

at the ISP. The ISP will often disable the customer's Internet

connection for security (and billing) reasons.

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For use in Cable Modems

y In addition to MAC addresses tracked by the ISP, some

broadband modems also track the MAC address of the host

computer's network adapter within the home network. If you

swap the computer connected to the broadband modem, or

change its network adapter, your cable Internet connection

may not function afterward.

y In this case, MAC address cloning is not required. Resetting

(including recycling power) on both the cable modem and

the host computer will automatically change the MAC

address stored inside the modem.

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Changing MAC Address

y There are several ways to change the MAC address from

which some of them are as follows:-

1)- Change a MAC Address through Cloning.

2)- Changing MAC Addresses through the Operating System.

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Change a MAC Address through

Cloning

y Change a MACAddress through Cloning

y Some people contact their ISP to request they update the

MAC address associated with their subscription. This process

works but takes time, andI

nternet service will be unavailablewhile waiting for the provider to take action.

y A better way to quickly workaround this problem is to

change the MAC address on the new device so that it matches

the address of the original device. While an actual physical

MAC address cannot be changed in hardware, the address can

be emulated in software. This process is called cloning.

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y Many broadband routers today support MAC address cloning

as an advanced configuration option. The emulated MAC

address appears to the service provider identical to theoriginal hardware address. The specific procedure of cloning

varies depending on the type of router; consult product

documentation for details.

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Changing MAC Addresses through the

OperatingSystem

y Starting with Windows 2000, users can sometimes change

their MAC address through the Windows My Network

Places interface. This procedure does not work for all

network cards as it depends on a certain level of software

support built into the adapter driver.

y In Linux and versions of Unix, the "ifconfig" also supports

changing MAC addresses if the necessary network card and

driver support exists.

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So this was all about MAC

Address and on this node myseminar presentation overs.

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seminaar ppt