The response of the Media Access Control Question
In recent weeks I have a lot 'of e-mails about Ethernet cards, both wired and wireless, and more specifically, about Media Access Control (MAC). I think the main reason that I have received many questions about Ethernet cards, and MAC addresses is people trying to own wireless home networks and their desire to use the MAC address filtering to secure. This type of filter in wireless networks can be configured toAllow or deny use of specific computers or connect to the wireless network based on the MAC.
My first thought was that of a single article on wireless Ethernet MAC addresses and write. After thinking, I decided to expand on this and to move some specific information about Ethernet cards and communication.
Different ways to find your MAC address and much more
There are several ways to Ethernet protocol and communication and information. Many Ethernet cardmanufacturer's proprietary software that can reveal this information, but behave differently depending on the manufacturer. So we'll use the Windows 2000 and XP "ipconfig" utility since this is available in most Windows operating systems.
First, go to "Start" -> "Run" and type "cmd" without quotes. Then press the Enter key. At the command prompt type "ipconfig / all", again without the quotes. In fact, just typing ipconfig without the '/ all will work, but it will onlyprovide summary information of network adapters. An example of what one might see by typing "ipconfig / all" command is below each said in green:
Fault Tolerant and High Availability Computer Systems
There are several ways to Ethernet protocol and communication and information. Many software vendors Ethernet card owners who can reveal this information, but behave differently depending on themanufacturer. So we'll use the Windows 2000 and XP "ipconfig" utility since this is available in most Windows operating systems.
First, go to "Start" -> "Run" and type "cmd" without quotes. Then press the Enter key. At the command prompt type "ipconfig / all", again without the quotes. In fact, just typing ipconfig without the '/ all will work, but provide only summary information of network adapters. An example of what one might see by typing"Ipconfig / all" command is as follows:
Output of "ipconfig / all" command
Windows IP Configuration
Host Name. . . . . . . . . . . . : Home Computer
This is the name of the computer, usually defined during the installation of Windows. However, it can be changed after installation.
Primary DNS Suffix.. . . . . . : Domain.com
If your computer has an active network, such as a Microsoft Windows domain this entry may contain the name ofdomain.
Node Type. . . . . . . . . . . . : Unknown
The node type can say unknown, or peer-to-peer, or in some cases "hybrid". It is an institution that has to do with Windows Internet Naming Services used in certain types of Windows domain networks.
IP Routing Enabled. . . . . . . . : No
This setting determines whether Windows XP or 2000 functions as an IP router. If you have two or more network cards you can configure the system to act as a router, forwarding communicationsrequests from one network to another. Windows 2000 can be configured to do this in a nice straight forward, Windows XP will need a change in the registry.
WINS Proxy Enabled. . . . . . . . : No
WINS Proxy is another institution that is linked to the "Node Type" we discussed earlier. It is not normally a required setting in a home or small office or the newer type of Microsoft Windows domains.
Ethernet adapter Wireless Network Connection 2:
If youover Ethernet (network) cards in your system, if I were in this laptop, you will have multiple listings. This is the second Ethernet card, a wireless Ethernet card inside.
Description. . . . . . . . . . . : Broadcom 802.11b / g WLAN
This is the description of the Ethernet card, usually the name / manufacturer and type of Ethernet card. In this case it is a Broadcom wireless Ethernet card built into my laptop.
Physical Address. . . . . . . . . :00-90-4B-F1-6E-4A
And here we have the MAC address. The MAC address is a 48-bit hexadecimal code and is suppose to be a completely unique address. It is 48 bits because each number or letter in hexadecimal represents 8 bits. Hexadecimal numbers range from 0,1,2,3,4,5,6,7,8,9, A, B, C, D, E, F. There are 6 alpha-numeric codes is 6 * 8 = 48 (bit). The first 3 codes identify the manufacturer of the card and the other codes are used to create a unique number. Theoretically there should never be acard with the same MAC address of a local network. However, there are some exceptions. There are software tools that allow you to change this code. In reality, this is a step some hackers take to attack other machines on a local network. I speak the local network because MAC addresses are not routable between network segments. By spoofing this address, you can impersonate another machine on the network. Traffic that was bound for the objective may be redirected to the hacker's computer. This isthe address is also possible to use a physical address or MAC address table before setting up wireless access point to support MAC address filtering to people.
DHCP enabled. . . . . . . . . . . : Yes
DHCP or Dynamic Host Control Protocol, if enabled means your computers IP address provided by a DHCP server on the network. The DHCP server can cable wireless access point / router DSL, cable modem or a network server. Although aDHCP server is enabled on the network, the computer operating system will automatically generate a random IP address within a predefined interval. This means you could network a group of interconnected, without having to manually assign the IP settings.
IP address. . . . . . . . . . . . : 192.168.0.117
This parameter allows your current IP address. The address above is what is called a "private" addresses. There are several classes of IP addressesare reserved for private use. This means that for the internal network, local or private home or office. Such addresses are not, or not, are routable on the Internet. The Internet routes called "valid" IP addresses. The cable / DSL router or cable modem has a valid IP address assigned to the "outside" of the network. The external interface of the phone or cable TV cable.
Subnet Mask. . . . . . . . . . . : 255.255.255.0
Subnet Mask is aspecial issue, or in a sense, the filter, which breaks your IP address, in this case a private IP address in certain areas. IP addresses and subnet mask can be a complicated issue and would require an entire article to be about.
Default Gateway. . . . . . . . . : 192.168.0.254
The default gateway IP addresses of the above, the IP address of the device that will route your request, such as when you try to browse a website on the Internet. It 's a bit complicatedthan that, but as a gateway or router traffic to different networks, the other private networks. At home or small office, this gateway most likely is your cable modem / DSL or router.
DHCP Server ... . . . . . . . . : 192.168.0.49
The DHCP server, remember we talked a bit 'above, the device indicates that the computer has an IP address and other information. DHCP server can assign all kinds of information, including: StandardGateway, DNS (Domain Name), IP address, Subnet Mask, Time Server, and more.
DNS Server ... . . . . . . . . : 192.168.0.49, 64.105.197.58
The DNS servers are internal or external, to fully resolve the names (FQDN), such as http://www.defendingthenet.com full domain of IP addresses. This is because computers are not really about your request using the domain, use the IP address assigned to the FQDN. For mosthome or small office, DNS server IP address from your primary Cable / DSL Router. The Cable / DSL Router to ask an external DNS server on the Internet to perform address the effective resolution of the FQDN to IP. The address 192.168.0.49 is an internal private device on my network that 64.105.197.58 is an external public Internet DNS server and is available in case my router has difficulty performing the DNSResolution tasks.
Lease obtained. . . . . . . . . . : Sunday, March 19, 2006 18:38:16
This information tells you when the computer received its IP address and other information from a DHCP server. You will notice that says "Lease obtained", it is because most of the DHCP server just give the IP address lease from a pool of addresses available. For example, the pool may be 192.168.1.1 through 192.168.1.50. So your DHCP server has 50 IP addresses to choose from whenassigning the IP address of your computer.
Lease expires. . . . . . . . . . : Wednesday, March 29, 2006 21:38:16
If the IP address assigned by the DHCP server will attempt to lease expiring lease is the same or a different IP address. This can usually be changed on the DHCP server. For example, on some fully functional DHCP server, you can never rent due within one day and so on.
Why are so MAC addressesImportant and how they work
To jump back into the MAC address for just a bit '. 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 local network, broadcasts a query, or ask a question, who owns a particular IP address. For example,The computer can say, "Who is 192.168.0.254". Using the information above, my default gateway is 192.168.0.254 and say "I am" 00-90-4B-F1-6E-4A "192.168.0.254". You send the MAC address. That the MAC address then in what is called a (ARP) Address Resolution Protocol table on your computer. You can use this information to the command prompt like you did above and typing "arp-a". You can obtain information such as the following:
Internet Address Physical AddressType
192.168.0.49 00-12-17-5C-A2-27 dynamic
192.168.0.109 00-12-17-5C-A2-27 dynamic
192.168.0.112 00-0C-76-93-94-b2 dynamic
192.168.0.254 00-0E-2E-2e-15-61 dynamic
How can a hacker use MAC addresses in an attack
You will notice that the IP addresses and the right of their MAC addresses. Without this information, without the MAC address, it would not be reading this right now. MAC addresses are not routable, such as IP addresses. They work on localor private network. However, the devices on the Internet, to perform the same tasks. Routers and switches keep a list of their colleagues MAC address devices such as computers and devices on your home or office network. I mentioned that MAC addresses can be modified to meet demand. For example, if I'm on your corporate network and you had an internal Web server that took personal information as input, I could tell the computer to my laptop for the websitebroadcasting my MAC address with the real web server IP address. I would do if the computer asks, "Who is the" Real Web Server ". I could set up a fake web server that looks just like the real thing, and start gathering information that the real web servers normally collect. You can see how it can be dangerous.
Conclusion
There are many other simple ways to protect your MAC address, but can be a bit 'of confusion if you have more than oneinternal network. Most external USB or PCMCIA wired and wireless Ethernet cards have their MAC address printed on them. Where the wired or wireless network adapter in your computer, such as in laptops, the MAC address is sometimes printed on the bottom of the laptop. Even Desktop systems cards that are inserted in PCI slots have the MAC address printed on the Ethernet card.
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