2024年5月30日发(作者：)

MAC地址

MAC地址1212

MAC（Media Access Control, 介质访问控制）MAC地址是烧录在Network Interface Card(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位叫做组织唯一标志符(organizationally unique ，是识别LAN（局

域网）节点的标识.24-47位是由厂家自己分配。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Windows 98/Me中，依次单击“开始”→“运行” →输入“winipcfg”→

回车。即可看到MAC地址。

在Windows 2000/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"Link Speed/Duplex Mode",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"Network Address"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"Network Address"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。

In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or

hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NIC or Network

Interface Card). It is a number that serves as an identifier for a particular network adapter. Thus network cards (or built-in

network adapters) in two different computers will have different MAC addresses, as would an Ethernet adapter and a wireless

adapter in the same computer, and as would multiple network cards in a router. However, it is possible to change the MAC

address on most of today's hardware, often referred to as MAC spoofing.

Most layer 2 network protocols use one of three numbering spaces managed by the Institute of Electrical and Electronics

Engineers (IEEE): MAC-48, EUI-48, and EUI-64, which are designed to be globally unique. Not all communications protocols

use MAC addresses, and not all protocols require globally unique identifiers. The IEEE claims trademarks on the names

"EUI-48" and "EUI-64" ("EUI" stands for Extended Unique Identifier).

MAC addresses, unlike IP addresses and IPX addresses, are not divided into "host" and "network" portions. Therefore, a

host cannot determine from the MAC address of another host whether that host is on the same layer 2 network segment as

the sending host or a network segment bridged to that network segment.

ARP is commonly used to convert from addresses in a layer 3 protocol such as Internet Protocol (IP) to the layer 2 MAC

address. On broadcast networks, such as Ethernet, the MAC address allows each host to be uniquely identified and allows

frames to be marked for specific hosts. It thus forms the basis of most of the layer 2 networking upon which higher OSI Layer

protocols are built to produce complex, functioning networks.

Contents [hide]

1 Notational conventions

2 Address details

2.1 Individual address block

3 Bit-reversed notation

4 See also

5 References

6 External links

[edit] Notational conventions

The standard (IEEE 802) format for printing MAC-48 addresses in human-readable media is six groups of two

hexadecimal digits, separated by hyphens (-) in transmission order, e.g. 01-23-45-67-89-ab. This form is also commonly used

for EUI-64. Other conventions include six groups of two separated by colons (:), e.g. 01:23:45:67:89:ab; or three groups of

four hexadecimal digits separated by dots (.), e.g. 0123.4567.89ab; again in transmission order.

[edit] Address details

The original IEEE 802 MAC address comes from the original Xerox Ethernet addressing scheme.[1] This 48-bit address

space contains potentially 248 or 281,474,976,710,656 possible MAC addresses.

All three numbering systems use the same format and differ only in the length of the identifier. Addresses can either be

"universally administered addresses" or "locally administered addresses."

A universally administered address is uniquely assigned to a device by its manufacturer; these are sometimes called

"burned-in addresses" (BIA). The first three octets (in transmission order) identify the organization that issued the identifier

and are known as the Organizationally Unique Identifier (OUI). The following three (MAC-48 and EUI-48) or five (EUI-64)

octets are assigned by that organization in nearly any manner they please, subject to the constraint of uniqueness. The IEEE

expects the MAC-48 space to be exhausted no sooner than the year 2100; EUI-64s are not expected to run out in the

foreseeable future.

A locally administered address is assigned to a device by a network administrator, overriding the burned-in address.

Locally administered addresses do not contain OUIs.

Universally administered and locally administered addresses are distinguished by setting the second least significant bit

of the most significant byte of the address. If the bit is 0, the address is universally administered. If it is 1, the address is

locally administered. The bit is 0 in all OUIs. For example, 02-00-00-00-00-01. The most significant byte is 02h. The binary is

00000010 and the second least significant bit is 1. Therefore, it is a locally administered address.[2]

If the least significant bit of the most significant byte is set to a 0, the packet is meant to reach only one receiving NIC.

This is called unicast. If the least significant bit of the most significant byte is set to a 1, the packet is meant to be sent only

once but still reach several NICs. This is called multicast.

MAC-48 and EUI-48 addresses are usually shown in hexadecimal format, with each octet separated by a dash or colon.

An example of a MAC-48 address would be "00-08-74-4C-7F-1D". If you cross-reference the first three octets with IEEE's OUI

assignments,[3] you can see that this MAC address came from Dell Computer Corp. The last three octets represent the serial

number assigned to the adapter by the manufacturer.

The following technologies use the MAC-48 identifier format:

Ethernet

802.11 wireless networks

Bluetooth

IEEE 802.5 token ring

most other IEEE 802 networks

FDDI

ATM (switched virtual connections only, as part of an NSAP address)

Fibre Channel and Serial Attached SCSI (as part of a World Wide Name)

The distinction between EUI-48 and MAC-48 identifiers is purely semantic: MAC-48 is used for network hardware; EUI-48

is used to identify other devices and software. (Thus, by definition, an EUI-48 is not in fact a "MAC address", although it is

syntactically indistinguishable from one and assigned from the same numbering space.)

The IEEE now considers the label MAC-48 to be an obsolete term which was previously used to refer to a specific type of

EUI-48 identifier used to address hardware interfaces within existing 802-based networking applications and should not be

used in the future. Instead, the term EUI-48 should be used for this purpose.

EUI-64 identifiers are used in:

FireWire

IPv6 (as the low-order 64 bits of a unicast network address when temporary addresses are not being used)

ZigBee / 802.15.4 wireless personal-area networks

The IEEE has built in several special address types to allow more than one Network Interface Card to be addressed at

one time:

Packets sent to the broadcast address, all one bits, are received by all stations on a local area network. In hexadecimal

the broadcast address would be "FF:FF:FF:FF:FF:FF".

Packets sent to a multicast address are received by all stations on a LAN that have been configured to receive packets

sent to that address.

Functional addresses identify one of more Token Ring NICs that provide a particular service, defined in IEEE 802.5.

These are "group addresses", as opposed to "individual addresses"; the least significant bit of the first octet of a MAC

address distinguishes individual addresses from group addresses. That bit is set to 0 in individual addresses and 1 in group

addresses. Group addresses, like individual addresses, can be universally administered or locally administered.

In addition, the EUI-64 numbering system encompasses both MAC-48 and EUI-48 identifiers by a simple translation

mechanism. To convert a MAC-48 into an EUI-64, copy the OUI, append the two octets "FF-FF", and then copy the

organization-specified part. To convert an EUI-48 into an EUI-64, the same process is used, but the sequence inserted is

"FF-FE". In both cases, the process can be trivially reversed when necessary. Organizations issuing EUI-64s are cautioned

against issuing identifiers that could be confused with these forms. The IEEE policy is to discourage new uses of 48-bit

identifiers in favor of the EUI-64 system.

IPv6—one of the most prominent standards that uses EUI-64—applies these rules inconsistently. Due to an error in the

appendix to the specification of IPv6 addressing, it is standard practice to extend MAC-48 addresses (such as IEEE 802 MAC

address) to EUI-64 using "FF-FE" rather than "FF-FF."

[edit] Individual address block

An Individual Address Block comprises a 24-bit OUI managed by the IEEE Registration Authority, followed by 12

IEEE-provided bits (identifying the organization), and 12 bits for the owner to assign to individual devices. An IAB is ideal for

organizations requiring fewer than 4097 unique 48-bit numbers (EUI-48).[4]

[edit] Bit-reversed notation

The standard transmission order notation for MAC addresses, as seen in the output of the ifconfig command for example,

is also called canonical format.

However, since IEEE 802.3 (Ethernet) and IEEE 802.4 (Token Bus) send the bits over the wire with least significant bit

first, while IEEE 802.5 (Token Ring) and IEEE 802.6 send the bits over the wire with most significant bit first, confusion may

arise where an address in the latter scenario is represented with bits reversed from the canonical representation. So for

instance, an address whose canonical form is 12-34-56-78-9A-BC would be transmitted over the wire as bits 01001000

00101100 01101010 00011110 01011001 00111101 in the standard transmission order (least significant bit first). But for

Token Ring networks, it would be transmitted as bits 00010010 00110100 01010110 01111000 10011010 10111100 in most

significant bit first order. If care is not taken to translate correctly and consistently to the canonical representation, the latter

might be displayed as 482C6A1E593D, which could cause confusion. This would be referred to as "Bit-reversed order",

"Non-canonical form", "MSB format", "IBM format", or "Token Ring format" as explained by RFC 2469. Canonical form is

preferred[who?].

[edit] See also

NSAP address, another endpoint addressing scheme.

Cisco Hot Standby Router Protocol or standard alternative VRRP Virtual router redundancy protocol, which allows

multiple routers to share one IP address and MAC address to provide router redundancy. The OpenBSD project has an open

source alternative, the Common Address Redundancy Protocol (CARP).

一般MAC地址在网卡中是固定的，当然也有网络高手会想办法去修改自己的MAC地址。修改自己的MAC地址有两种方法，一种是硬件修改，另外一种是软

件修改。硬件的方法就是直接对网卡进行操作，修改保存在网卡的EPROM里面的MAC地址，通过网卡生产厂家提供的修改程序可以更改存储器里的地址。

那么什么叫做EPROM呢？EPROM是电子学中一种存储器的专业术语，它是可擦写的，也就是说一张白纸你用钢笔写了一遍以后就不能再用橡皮擦去了，而

EPROM这张白纸用铅笔写后可以再擦去，可以反复改变其中数据的存储器。当然软件修改的方法就相对来说要简单得多了，在Windows中，网卡的MAC保

存在注册表中，实际使用也是从注册表中提取的，所以只要修改注册表就可以改变MAC。Windows 9x中修改：打开注册表编辑器，在

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceClassNet下的0000，0001，0002。

Windows 2000/XP中的修改：同样打开注册表编辑器，

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass4D36E970-E325-11CE-BFC1-08002BE10318 中的0000，0001，0002中的DriverDesc，

如果在0000找到，就在0000下面添加字符串变量，命名为“NetworkAddress”，值为要设置的MAC地址，例如：

完成上述操作后重启就好了。一般网卡发出的包的源MAC地址并不是网卡本身写上去的，而是应用程序提供的，只是在通常的实现中，应用程序先从网卡上

得到MAC地址，每次发送的时候都用这个MAC作为源MAC而已，而注册表中的MAC地址是在Windows安装的时候从网卡中读入的，只要你的操作系统不

重新安装应该侍獠淮蟆?