“Media Access Control”. Nothing to do with the Macintosh.
In the world of hacking and specially Networking, you will often come
across this term “MAC Address”. It is used in various hacks, but the
majority doesn’t even knows what it is. So What exactly is it? What does
it do? How it is used? Is it related to IP address?
The
Media Access Control (MAC) address is a binary number used to uniquely
identify computer network adapters. These numbers (sometimes called
“hardware addresses”) are physically burned into the network hardware
during the manufacturing process, or stored in firmware, and designed to
not be modified. Some refer to them as “Ethernet addresses” for
historical reasons, but most popular types of networks utilize MAC
addressing including Ethernet, WiFi and Bluetooth.
Format of a MAC Address:
MMM.MMM.SSS.SSS
The leftmost 6 digits (24 bits) called “prefix” are associated with the
adapter manufacturer. Each vendor registers and obtains MAC prefixes as
assigned by the IEEE (Institute of Electrical and Electronics
Engineers). Vendors often possess many prefix numbers associated with
their different products. For example, the prefixes:
00:13:10, 00:25:9C and 68:7F:74 (plus many others) all belong to Linksys (Cisco Systems).
The rightmost digits of a MAC address represent an identification number
for the specific device. Among all devices manufactured with the same
vendor prefix, each is given their own unique 24-bit number. Note that
hardware from different vendors may happen to share the same device
portion of the address.
64-bit MAC Addresses:
While traditional MAC addresses are all 48 bits
in length, a few types of networks require 64-bit addresses instead.
“ZigBee” wireless home automation and other similar networks based on
“IEEE 802.15.4″, for example, require 64-bit MAC addresses to be
configured on their hardware devices. TCP/IP networks based on IPv6 also
implement a different approach to communicating with MAC addresses
compared to mainstream IPv4. Instead of 64-bit hardware addresses.
(TECHNICAL: IPv6 automatically translates 48-bit MAC address to a 64-bit
address by inserting a fixed (hardcoded) 16-bit value in between the
vendor prefix and the device identifier. IPv6 calls these numbers
“identifiers” to distinguish them from true 64-bit hardware addresses.)
For example, a 48-bit MAC address-
00:25:96:12:34:56 might appear on an IPv6 network as say for example, in either of these two forms:
00:25:96:FF:FE:12:34:56
0025:96FF:FE12:3456
(They simply add in the remaining 16 bits containing known characters at
a known position so it can be easily converted back and forth, if
needed to. In above case, “FFFE” fills up the requirement.)
MAC vs. IP Address Relationship
TCP/IP networks use
both MAC addresses and IP addresses but for separate purposes. A MAC
address remains fixed to the device’s hardware while the IP address for
that same device can be changed depending on its TCP/IP network
configuration and ISP. Media Access Control operates at one Layer of the
OSI model (Open Systems Interconnection) while Internet Protocol
operates at another Layer, meaning they each do their own tasks without
interfering with each other. This allows MAC addressing to support other
kinds of networks besides TCP/IP.
IP networks manage the conversion between IP and MAC addresses using
Address Resolution Protocol (ARP). Basically, ARP defines a set of rules
according to which IP and MAC addresses can be related. So, all in all
MAC addresses are simply a unique number assigned to a Network adapter.
They help identifying the specific device to which a specific packet of
information must reach in order to create a successful connection to
exchange data. You need an address to send a mail, right? That is just
what MAC addresses brings to the table.