MAC stands for Media Access Control.
MAC address is defined as the identification number for the hardware. In general, the network interface cards (NIC) of each computer such as Wi-Fi Card, Bluetooth or Ethernet Card has unchangeable MAC address embedded by the vendor at the time of manufacturing. Dell, Nortel, Belkin, and Cisco are some of the well known NIC manufacturers. One can change the given default address of the device by replacing the NIC cards.
As far as history, we can say that Xerox PARC scientists have created the existence of Media Access Control addresses. There are many similar terms that are used in place of MAC address such as hardware address, physical address, ethernet hardware address of a network device. Even burned-in address (BIA especially for Cisco Router Switches) also referred to as the same.
- The MAC address that is considered to be the distinguishing number of the hardware is globally unique. This lets us identify each device within a connected network.
- The total length MAC address in byte is 6 (or 48 bits). According to the IEEE 802 standards, this address is written in three commonly used formats:
- Six two-digits hexadecimals separated by hyphens (-) like 45-67-89-AB-12-CD .
- Six two-digits hexadecimals separated by colons (:) like 45:67:89:AB:DE:23 .
- Four three-digits hexadecimals separated by dots (.) like ABCD.4567.1238 .
The possible MAC addresses that can be formed by the address space is about 2^48 (over 281 trillion).
- The right 24 bits (4 bytes) of the address is termed as Organizationally Unique Identifier (OUI) number. This OUI number is assigned by Internet Assigned Number Authority (IANA). This globally unique OUI number will always remain the same for NICs manufactured by the same company. The left 24 bits (4 bytes) of the address is termed as Network Interface Controller Specific (NICS), which is responsible for communication either by using cables or wirelessly over a computer network.
- Some devices that exist on this second layer are NIC cards, bridges and switches. This layer is also responsible for error free data transmission over the Physical layer under LAN transmissions. If we refer to our Open Systems Interconnection (OSI) network model, we will find that MAC addresses in the medium access control protocol sub-layer uses data link layer.
- The devices that connect to the network have no or free attachment cost associated with it.
- The router or switch has policy set on them. Either it has permitted equipment attached or non-permitted equipment attached irrespective of the person attaching it.
- The MAC addresses for all the devices on the same network subnet are different. Hence, Diagnosing Network issues relating to IP address, etc. are easy because of the usefulness of MAC Addresses.
- A network administrator feels reliability in identifying senders and receivers of data on the network with the help of MAC address. The only reason behind is that unlike dynamic IP addresses, the MAC addresses doesn’t change from time to time.
- Due to the reason that the first three bytes (OUI) for a MAC address reserved for the manufacturer, therefore it is limited for having only be 2^24 unique addresses per OUI by the same manufacturer.
- We can say spoofing is easy for MAC address filtering. One can act in disguise and just listen to and from permitted MAC addresses because of the broadcast nature of ethernet.
- In most cases an intruder can obtain access to the network by constantly changing his MAC Address to a one that is permitted.
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