mac介质访问控制地址

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MAC地址开放分类：网络、电脑、网卡MAC地址1212MAC（MediaAccessControl,介质访问控制）MAC地址是烧录在NetworkInterfaceCard(网卡,NIC)里的.MAC地址,也叫硬件地址,是由48比特长(6字节),16进制的数字组成.0-23位是由厂家自己分配.24-47位,叫做组织唯一标志符(organizationallyunique，是识别LAN（局域网）节点的标识。其中第40位是组播地址标志位。网卡的物理地址通常是由网卡生产厂家烧入网卡的EPROM（一种闪存芯片，通常可以通过程序擦写），它存储的是传输数据时真正赖以标识发出数据的电脑和接收数据的主机的地址。也就是说，在网络底层的物理传输过程中，是通过物理地址来识别主机的，它一般也是全球唯一的。比如，著名的以太网卡，其物理地址是48bit（比特位）的整数，如：44-45-53-54-00-00,以机器可读的方式存入主机接口中。以太网地址管理机构(除了管这个外还管别的)（IEEE）（IEEEE：电气和电子工程师协会）将以太网地址，也就是48比特的不同组合，分为若干独立的连续地址组，生产以太网网卡的厂家就购买其中一组，具体生产时，逐个将唯一地址赋予以太网卡。形象的说，MAC地址就如同我们身份证上的身份证号码，具有全球唯一性。如何获取本机的MAC？对于数量不多的几台机器，我们可以这样获取MAC地址：在Windows98/Me中，依次单击“开始”→“运行”→输入“winipcfg”→回车。即可看到MAC地址。在Windows2000/XP中，依次单击“开始”→“运行”→输入“CMD”→回车→输入“ipconfig/all”→回车。即可看到MAC地址。修改网卡MAC地址的方法　　其实更改网卡MAC地址的功能不论98、2000还是XP，都已经提供了，只是平时大家都没有注意到而以。下面我就说说怎么更改。很简单哦。。。　　好了，现在先来看看WIN2000。在桌面上网上邻居图标上点右键，选"属性"，在出来的"网络和拨号连接"窗口中一般有两个图标，一个是"新建连接"图标，一个是"我的连接"图标。如果你的机器上有两个网卡的话，那就有三个图标了。如果你只有一个网卡，那就在"我的连接"图标上点右键，选"属性"，会出来一个"我的连接属性"的窗口。在图口上部有一个"连接时使用："的标识，下面就是你机器上的网卡型号了。在下面有一个"配置"按钮，点击该按钮后就进入了网卡的属性对话框了，这个对话框中有五个属性页，点击第二项"高级"页，在"属性"标识下有两项：一个是"LinkSpeed/DuplexMode",这是设置网卡工作速率的，我们需要改的是下面一个"Network Address",点击该项，在对话框右边的"值"标识下有两个单选项，默认得是"不存在"，我们只要选中上面一个单选项，然后在右边的框中输入你想改的网卡MAC地址，点"确定"，等待一会儿，网卡地址就改好了，你甚至不用停用网卡！　　另外，你也可以在"设置管理器"中，打开网卡的属性页来修改，效果一样。WINXP的修改方法跟WIN2000一样。　　在98下面修改和WIN2000、XP下差不多。在"网上邻居"图标上点右键，选择"属性"，出来一个"网络"对话框，在"配置"框中，双击你要修改的网卡，出来一个网卡属性对话框。在"高级"选项中，也是点击"属性"标识下的"NetworkAddress"项，在右边的两个单选项中选择上面一个，再在框中输入你要修改的网卡MAC地址，点"确定"后，系统会提示你重新启动。重新启动后，你的网卡地址就告修改成功！！　　如果你想把网卡的MAC地址恢复原样，只要再次把"NetworkAddress"项右边的单选项选择为下面一个"没有显示"再重新启动即可。在WIN2000、XP下面是选择"不存在"，当然也不用重新启动了。IncomputernetworkingaMediaAccessControladdress(MACaddress)orEthernetHardwareAddress(EHA)orhardwareaddressoradapteraddressisaquasi-uniqueidentifierattachedtomostnetworkadapters(NICorNetworkInterfaceCard).Itisanumberthatservesasanidentifierforaparticularnetworkadapter.Thusnetworkcards(orbuilt-innetworkadapters)intwodifferentcomputerswillhavedifferentMACaddresses,aswouldanEthernetadapterandawirelessadapterinthesamecomputer,andaswouldmultiplenetworkcardsinarouter.However,itispossibletochangetheMACaddressonmostoftoday'shardware,oftenreferredtoasMACspoofing.Mostlayer2networkprotocolsuseoneofthreenumberingspacesmanagedbytheInstituteofElectricalandElectronicsEngineers(IEEE):MAC-48,EUI-48,andEUI-64,whicharedesignedtobegloballyunique.NotallcommunicationsprotocolsuseMACaddresses,andnotallprotocolsrequiregloballyuniqueidentifiers.TheIEEEclaimstrademarksonthenames"EUI-48"and"EUI-64"("EUI"standsforExtendedUniqueIdentifier).MACaddresses,unlikeIPaddressesandIPXaddresses,arenotdividedinto"host"and"network"portions.Therefore,ahostcannotdeterminefromtheMACaddressofanotherhostwhetherthathostisonthesamelayer2networksegmentasthesendinghostoranetworksegmentbridgedtothatnetworksegment.ARPiscommonlyusedtoconvertfromaddressesinalayer3protocolsuchasInternetProtocol(IP)tothelayer2MACaddress.Onbroadcastnetworks,suchasEthernet,theMACaddressallowseachhosttobeuniquelyidentifiedandallowsframestobemarkedforspecifichosts.Itthusformsthebasisofmostofthelayer2networkinguponwhichhigherOSILayerprotocolsarebuilttoproducecomplex,functioningnetworks.Contents[hide]1Notationalconventions2Addressdetails2.1Individualaddressblock 3Bit-reversednotation4Seealso5References6Externallinks[edit]NotationalconventionsThestandard(IEEE802)formatforprintingMAC-48addressesinhuman-readablemediaissixgroupsoftwohexadecimaldigits,separatedbyhyphens(-)intransmissionorder,e.g.01-23-45-67-89-ab.ThisformisalsocommonlyusedforEUI-64.Otherconventionsincludesixgroupsoftwoseparatedbycolons(:),e.g.01:23:45:67:89:ab;orthreegroupsoffourhexadecimaldigitsseparatedbydots(.),e.g.0123.4567.89ab;againintransmissionorder.[edit]AddressdetailsTheoriginalIEEE802MACaddresscomesfromtheoriginalXeroxEthernetaddressingscheme.[1]This48-bitaddressspacecontainspotentially248or281,474,976,710,656possibleMACaddresses.Allthreenumberingsystemsusethesameformatanddifferonlyinthelengthoftheidentifier.Addressescaneitherbe"universallyadministeredaddresses"or"locallyadministeredaddresses."Auniversallyadministeredaddressisuniquelyassignedtoadevicebyitsmanufacturer;thesearesometimescalled"burned-inaddresses"(BIA).Thefirstthreeoctets(intransmissionorder)identifytheorganizationthatissuedtheidentifierandareknownastheOrganizationallyUniqueIdentifier(OUI).Thefollowingthree(MAC-48andEUI-48)orfive(EUI-64)octetsareassignedbythatorganizationinnearlyanymannertheyplease,subjecttotheconstraintofuniqueness.TheIEEEexpectstheMAC-48spacetobeexhaustednosoonerthantheyear2100;EUI-64sarenotexpectedtorunoutintheforeseeablefuture.Alocallyadministeredaddressisassignedtoadevicebyanetworkadministrator,overridingtheburned-inaddress.LocallyadministeredaddressesdonotcontainOUIs.Universallyadministeredandlocallyadministeredaddressesaredistinguishedbysettingthesecondleastsignificantbitofthemostsignificantbyteoftheaddress.Ifthebitis0,theaddressisuniversallyadministered.Ifitis1,theaddressislocallyadministered.Thebitis0inallOUIs.Forexample,02-00-00-00-00-01.Themostsignificantbyteis02h.Thebinaryis00000010andthesecondleastsignificantbitis1.Therefore,itisalocallyadministeredaddress.[2]Iftheleastsignificantbitofthemostsignificantbyteissettoa0,thepacketismeanttoreachonlyonereceivingNIC.Thisiscalledunicast.Iftheleastsignificantbitofthemostsignificantbyteissettoa1,thepacketismeanttobesentonlyoncebutstillreachseveralNICs.Thisiscalledmulticast.MAC-48andEUI-48addressesareusuallyshowninhexadecimalformat,witheachoctetseparatedbyadashorcolon.AnexampleofaMAC-48addresswouldbe"00-08-74-4C-7F-1D".Ifyoucross-referencethefirstthreeoctetswithIEEE'sOUIassignments,[3]youcanseethatthisMACaddresscamefromDellComputerCorp.Thelastthreeoctetsrepresenttheserialnumberassignedtotheadapterbythemanufacturer.ThefollowingtechnologiesusetheMAC-48identifierformat:Ethernet 802.11wirelessnetworksBluetoothIEEE802.5tokenringmostotherIEEE802networksFDDIATM(switchedvirtualconnectionsonly,aspartofanNSAPaddress)FibreChannelandSerialAttachedSCSI(aspartofaWorldWideName)ThedistinctionbetweenEUI-48andMAC-48identifiersispurelysemantic:MAC-48isusedfornetworkhardware;EUI-48isusedtoidentifyotherdevicesandsoftware.(Thus,bydefinition,anEUI-48isnotinfacta"MACaddress",althoughitissyntacticallyindistinguishablefromoneandassignedfromthesamenumberingspace.)TheIEEEnowconsidersthelabelMAC-48tobeanobsoletetermwhichwaspreviouslyusedtorefertoaspecifictypeofEUI-48identifierusedtoaddresshardwareinterfaceswithinexisting802-basednetworkingapplicationsandshouldnotbeusedinthefuture.Instead,thetermEUI-48shouldbeusedforthispurpose.EUI-64identifiersareusedin:FireWireIPv6(asthelow-order64bitsofaunicastnetworkaddresswhentemporaryaddressesarenotbeingused)ZigBee/802.15.4wirelesspersonal-areanetworksTheIEEEhasbuiltinseveralspecialaddresstypestoallowmorethanoneNetworkInterfaceCardtobeaddressedatonetime:Packetssenttothebroadcastaddress,allonebits,arereceivedbyallstationsonalocalareanetwork.Inhexadecimalthebroadcastaddresswouldbe"FF:FF:FF:FF:FF:FF".PacketssenttoamulticastaddressarereceivedbyallstationsonaLANthathavebeenconfiguredtoreceivepacketssenttothataddress.FunctionaladdressesidentifyoneofmoreTokenRingNICsthatprovideaparticularservice,definedinIEEE802.5.Theseare"groupaddresses",asopposedto"individualaddresses";theleastsignificantbitofthefirstoctetofaMACaddressdistinguishesindividualaddressesfromgroupaddresses.Thatbitissetto0inindividualaddressesand1ingroupaddresses.Groupaddresses,likeindividualaddresses,canbeuniversallyadministeredorlocallyadministered.Inaddition,theEUI-64numberingsystemencompassesbothMAC-48andEUI-48identifiersbyasimpletranslationmechanism.ToconvertaMAC-48intoanEUI-64,copytheOUI,appendthetwooctets"FF-FF",andthencopytheorganization-specifiedpart.ToconvertanEUI-48intoanEUI-64,thesameprocessisused,butthesequenceinsertedis"FF-FE".Inbothcases,theprocesscanbetriviallyreversedwhennecessary.OrganizationsissuingEUI-64sarecautionedagainstissuingidentifiersthatcouldbeconfusedwiththeseforms.TheIEEEpolicyistodiscouragenewusesof48-bitidentifiersinfavoroftheEUI-64system.IPv6—oneofthemostprominentstandardsthatusesEUI-64—appliestheserulesinconsistently.DuetoanerrorintheappendixtothespecificationofIPv6addressing,itisstandardpracticetoextendMAC-48addresses(suchasIEEE802MACaddress)toEUI-64using"FF-FE"ratherthan "FF-FF."[edit]IndividualaddressblockAnIndividualAddressBlockcomprisesa24-bitOUImanagedbytheIEEERegistrationAuthority,followedby12IEEE-providedbits(identifyingtheorganization),and12bitsfortheownertoassigntoindividualdevices.AnIABisidealfororganizationsrequiringfewerthan4097unique48-bitnumbers(EUI-48).[4][edit]Bit-reversednotationThestandardtransmissionordernotationforMACaddresses,asseenintheoutputoftheifconfigcommandforexample,isalsocalledcanonicalformat.However,sinceIEEE802.3(Ethernet)andIEEE802.4(TokenBus)sendthebitsoverthewirewithleastsignificantbitfirst,whileIEEE802.5(TokenRing)andIEEE802.6sendthebitsoverthewirewithmostsignificantbitfirst,confusionmayarisewhereanaddressinthelatterscenarioisrepresentedwithbitsreversedfromthecanonicalrepresentation.Soforinstance,anaddresswhosecanonicalformis12-34-56-78-9A-BCwouldbetransmittedoverthewireasbits010010000010110001101010000111100101100100111101inthestandardtransmissionorder(leastsignificantbitfirst).ButforTokenRingnetworks,itwouldbetransmittedasbits000100100011010001010110011110001001101010111100inmostsignificantbitfirstorder.Ifcareisnottakentotranslatecorrectlyandconsistentlytothecanonicalrepresentation,thelattermightbedisplayedas482C6A1E593D,whichcouldcauseconfusion.Thiswouldbereferredtoas"Bit-reversedorder","Non-canonicalform","MSBformat","IBMformat",or"TokenRingformat"asexplainedbyRFC2469.Canonicalformispreferred[who?].