The MAC Address Of Wired And Wireless Network Cards

In recent weeks, I received quite a few e-mails about Ethernet cards, both wired and wireless, and more specifically, about Media Access Control (MAC)-address. I think the main reason why I got so many questions about Ethernet cards and MAC addresses is people trying to secure their wireless networks at home and their desire to use MAC address filtering. This type of filtering in wireless networks can be configured to allow or deny specific computers to use or join the wireless network based on MAC address.

My first thought was to write an article just about MAC addresses and wireless Ethernet. Upon reflection, I decided to expand on this and go over some specific information about Ethernet cards and communication.

Different ways to find your MAC address, and more


There are many ways of finding your Ethernet and communications protocol information. Many Ethernet card manufacturers have proprietary software that can reveal this information but they work differently, depending on manufacturer. Therefore, use the Windows 2000 and XP "ipconfig" utility since this is available on most Windows operating systems.

First, go to "Start" -> "Run" and type "cmd" without quotes. Then press the Enter key. On the command line, type "ipconfig / all", again without the quotes. In fact, just typing ipconfig without work / all, but will only give you information about your network cards short. An example of what you can see by typing "ipconfig / all" command below with each item commented in green lettering:

Very tolerant to faults and the availability of computer systems


There are several ways to find the Ethernet and communications protocol information. Many Ethernet card manufacturer's have proprietary software that can reveal this information, but work differently depending on the manufacturer. So we use Windows 2000 and XP utility "ipconfig" from the time that is available on most Windows operating systems.

First of all, go to "Start" -> "Run" and type "cmd" without the quotes. Then press Enter. From the command line type "ipconfig / all", again without the quotes. In fact, just typing ipconfig without the '/ all the works, but only to provide abbreviated information about network adapters. An example of what you might see by typing "ipconfig / all" command is below:

The output of "ipconfig / all"

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Windows IP Configuration

Host Name. . . . . . . . . . . . : Home Computer

This is the name of the computer, typically defined during the installation of Windows. However, it can be changed after installation.

Primary DNS suffix. . . . . . . :

If your computer participates in a network, such as a Microsoft Windows This article may contain the domain name.

Node Type. . . . . . . . . . . . : Unknown

The node type may say Unknown, or peer-to-peer, or in some cases "hybrid". This is a parameter that has to do with the Internet name service of Windows used in certain types of Windows domain networks.

IP Routing Enabled. . . . . . . . : No

This option determines whether Windows XP or 2000 functions as an IP router. If you have two or more network cards, configure the system to act as a router, the transmission of requests from one network to another. Windows 2000 can be configured to do so in a fairly simple Windows XP requires a registry change.

WINS Proxy Enabled. . . . . . . . : No

WINS Proxy is another setting that refers to "Node Type" we discussed earlier. It is not normally necessary to set up a home network or small office areas or the latest Microsoft Windows.

Ethernet adapter Wireless Network Connection 2:

If you have multiple Ethernet (network) cards in your systems, as I do in this laptop, you will have multiple listings. This happens to be the second Ethernet card, an internal wireless ethernet cards.

Description. . . . . . . . . . . Broadcom 802.11b / g Wi-Fi

This is a description of the Ethernet card, usually in the name / manufacturer and type of Ethernet card. In this case, it is a Broadcom wireless Ethernet card built into my laptop.

The physical address. . . . . . . . . : 00-90-4B-F1-6E-4A

And here we have the MAC address. The MAC address is a hexadecimal 48-bit is supposed to be a unique address. It is 48 bits because each number or letter in hexadecimal represents 8 bits. Hexadecimal numbers 0,1,2,3,4,5,6,7,8,9 large as A, B, C, D, E, F are six alphanumeric codes are 6 * 8 = 48 (bits). The first three codes identify the manufacturer of the card and the remaining codes are used to create a unique number. Theoretically, it should never be a card with the same MAC address on a LAN. There are some exceptions. There are software tools that allow you to change the code. In fact, it is a step some hackers take to attack other systems on a LAN. I say local network because MAC addresses are not routable between network segments. By spoofing this address, you can publish to another machine on the LAN. Traffic that was bound to the objective pursued can be redirected to the attacker's machine.

DHCP enabled. . . . . . . . . . . : Yes

DHCP, or Dynamic Host Control Protocol, if enabled means your computers IP address is supplied by a DHCP server on your network. The DHCP server can be your wireless access point, cable / DSL router, cable modem, or a server on your network. Also, if a DHCP server is not enabled on your network, your computers operating system will automatically generate a random IP address in a predefined interval. That means you could network a group of systems together without having to manually assign the IP settings.

IP address. . . . . . . . . . . . :

This setup gives you your current IP address. The address above is called a "private" address. There are certain classes of IP addresses that are reserved for private use. This means that your internal network, local or private home or office. These addresses are not or should not be routable on the Internet. Internet clues to what is called "valid" IP addresses. Your Cable / DSL router or cable modem has an IP address assigned to network interface "external". The external interface may be your phone line or cable TV cable.

Subnet Mask. . . . . . . . . . . :

Subnet mask is a special number, or in a sense, a filter, which breaks down the IP address, in this case the private IP address, to certain groups. IP addresses and subnet mask can be complex and would require an entire article to go further.

Default Gateway. . . . . . . . . :

Default Gateway, IP addresses of the above, the IP address of a device that sends your request, like when you try to navigate the site, the Internet. It 'a little' more complicated, also act as a gateway or router can route traffic to different networks, but also other private networks. Home or office, this gateway is likely that the cable / DSL modem or router.

DHCP server. . . . . . . . . . . :

DHCP server, I remember we talked a little 'before, is a device that identifies the computer's IP address and other information. DHCP server can provide any kind of information, such as the default gateway, DNS server (Domain Name), IP address, Subnet Mask, Time Server, and more.

DNS servers. . . . . . . . . . . :,

DNS Servers are internal or external servers that resolve domain names (FQDN) and IP addresses This is because computers are not actually transmit your requests with the domain name, you use the IP address assigned to the FQDN. For users of most home or small office, the DNS server is the IP address of your cable / DSL router. Your cable / DSL router that requests an external DNS server on the Internet for the resolution of the FQDN to an IP address. The address is a domestic private on my network, whereas the is an external Internet DNS server, and is present only in the case of my router has trouble performing the DNS resolution tasks.

Lease Obtained. . . . . . . . . . : Sunday, March 19, 2006 06:38:16

This information tells you when your computer has an IP address and other information about the DHCP server. You will notice that says "Lease Obtained", that is, because most of the DHCP servers only lease the IP address of the pool of available addresses. For example, the pool may be with So the DHCP server has 50 IP addresses to choose from when you configure the IP address of the computer.

Lease expires. . . . . . . . . . : Wednesday, March 29, 2006 9:38:16 pm

When the IP address assigned by the DHCP server lease expires try to hire you or another IP address. This feature can be changed at the DHCP server. For example, in some fully functional DHCP servers, you can set the lease never expires, or within one day and so on.

Why are the MAC addresses so important and how they work

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To return to the MAC address for just a little. You might think that IP addresses are the most important thing when it comes to network communication. The reality is, MAC addresses are very important because without them computers would not be able to communicate over Ethernet networks. When a computer wants to talk to another computer on a LAN, it will broadcast a request or ask a question that has a specific IP address. For example, your computer may say "Who is". Using the information above, my default gateway is and will answer "I" 00-90-4B-F1-6E-4A "192,168. 0254 ". It returns its MAC address. The MAC address is then passed through what is called an Address Resolution Protocol (ARP) on your computer. You can view this information by going to the command you've done above and typing "arp-a". You can obtain information as follows:

Internet Address Type Physical Address 17.12.00-5C-A2-27 dynamic 00-12-17-5c-27-A2, a dynamic 00-0c-76-93-94-B2 dynamic 00-0e-2e-2e-15-61 dynamic

How a hacker could use the MAC address of attack


Notice that the IP addresses and to the right of their MAC addresses. Without this information, without MAC address, you will not be reading this article right now. MAC addresses are not routed IP addresses. They work on your LAN or private. But the devices on the Internet perform the same tasks. Routers and switches keep a list of MAC address peer devices such as computers and devices on your home network or office. I mentioned above that MAC addresses can be modified to redirect requests. For example, if I were in your office network and you had an internal Web server that took personal information as input, I could tell your computer to access my laptop on the site by sending my MAC address tied to the real web servers IP address. I want to do when your computer asked "Who is the" real web server "."



There are several other easy ways you can find your MAC address, but can be a bit confusing if you have more than one internal network card. More USB or PCMCIA external wired and wireless Ethernet cards have their MAC address printed on them. In cases where the wireless network card or within your computer, such as laptops, the MAC address is sometimes printed on the bottom of the notebook. Even Desktop systems cards that are inserted into PCI slots have the MAC address printed on the Ethernet card.

This is the address that you also use it to fill a table of MAC addresses or physical address to configure your wireless access point to support MAC address filtering.

I could install a fraudulent Web server that looks like the real thing, and start collecting information on the real web server would normally collect. You can see how it can be dangerous.


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