What is a MAC Address? Everything about MAC addresses

Published on August 31, 2022

MAC Address

Everything you wanted to know about MAC addresses is in this article. If you do not find what you were looking for, please contact me and I will add the relevant information to this article.

What is an IP Address Explained | T...
What is an IP Address Explained | Tech Education

What is a MAC Address?

A Media Access Control (MAC) address is a hardware identification hexadecimal number that uniquely identifies each device on a network. Every network card (Ethernet or wireless) or Bluetooth device comes with a preset MAC address and cannot be changed.

In the past, MAC addresses were also called Ethernet addresses, but these days, MAC addresses also apply to wireless (Wi-Fi) and Bluetooth networks.

A MAC address is associated with the Network Interface Controller (NIC), which makes the physical connection to the network. This is done by by plugging the network card using an ethernet cable or connecting wirelessly to a Wi-Fi network or via Bluetooth.

Binary, Decimal and Hexadecimal number systems

Before we start, here is a table showing the decimal, binary and hexadecimal number equivalents.

Decimal Binary (4-bit) Hexadecimal
0 0000 0
1 0001 1
2 0010 2
3 0011 3
4 0100 4
5 0101 5
6 0110 6
7 0111 7
8 1000 8
9 1001 9
10 1010 A
11 1011 B
12 1100 C
13 1101 D
14 1110 E
15 1111 F

MAC address formats

A MAC address consists of 6 bytes or 12 hexadecimal digits or 48 bits.

If you recall middle school or high school mathematics, 8 bits = 1 byte. That means 6 bytes = 6 x 8 = 48 bits. You can also group 4 bits into 1 hexadecimal digit, so 48 bits = 12 hexadecimal digits.

By default, a MAC address is written in this format using colons as delimiter. X represents a hexadecimal digit.

XX:XX:XX:XX:XX:XX

MAC addresses can also be written using hyphen as delimiter.

XX-XX-XX-XX-XX-XX

MAC addresses can also use dots as delimiter.

XX.XX.XX.XX.XX.XX

OUI address and NIC address

The OUI address is the first 3 bytes. The NIC address is the next 3 bytes.

As an example, let us look at this MAC address 00:12:34:56:78:9E.

The first 3 bytes 00:12:34 correspond to the OUI.

The last 3 bytes 56:78:9E correspond to the NIC.

OUI NIC
00:12:34 56:78:9E

What are MAC address block sizes?

There are 3 MAC address block sizes: MA-L, MA-M and MA-S.

MAC Address Block Sizse MA-L, MA-M, MA-S

MAC Address Block Large (MA-L)

MA-L block size, or MAC Address - Large, was previously called OUI (Organizationally Unique Identifier). It is a 24-bit identifier. This MAC address block can contain 224 = 16 million MAC addresses.

Example: The MAC address FA:8F:CA:00:11:11 is a large block ML-A that is assigned to Chromecast devices. This MAC address block belongs to Google.

The range of this block is from FA:8F:CA:00:00:00 to FA:8F:CA:FF:FF:FF. The last 3 bytes would take all variations. That would be a total of 28 x 28 x 28 = 224 = 16 million MAC addresses.

MAC Address Block Medium (MA-M)

MA-M block size, or MAC Address - Medium, is a 28-bit identifier. This is combined with 20 organizational bits to form EUI-48 addresses. In some cases, it can be combined with 36 organizational bits to form EUI-64 addresses. This MAC address block can contain 220 = 1 million MAC addresses.

Example: The MAC address range D4:BA:BA:A0:00:00 to D4:BA:BA:AF:FF:FF is a medium block ML-M that is assigned to Actiontec devices.

The last 20 bits will take all variations. That would be a total of 220 = 1 million MAC addresses.

MAC Address Block Small (MA-S)

MA-S block size, or MAC Address - Small, was previously called OUI-36. It is a 36-bit identifier. This is combined with 12 organizational bits to form EUI-48 addresses. In some cases, it can be combined with 28 organizational bits to form EUI-64 addresses. This MAC address block can contain 212 = 4096 MAC addresses.

Example: The MAC address range 8C:1F:64:A2:D0:00 to 8C:1F:64:A2:DF:FF is a medium block ML-M that is assigned to Actiontec devices.

The last 12 bits will take all variations. That would be a total of 212 = 4096 MAC addresses.

What is MAC address cloning?

MAC address cloning is the process of copying the MAC address of an approved device on the network or assigning a new MAC address to a device if there are network or connectivity problems.

For example, if a laptop has a problem connecting to the home Wi-Fi, the connectivity issue can be resolved by finding a valid or approved device (another laptop, maybe), and assigning the MAC address of the second laptop to the first laptop. Also, some providers would require you to clone your laptop with the MAC address of the router.

Can you ping to a MAC address?

No, you cannot ping to a MAC address, but you can ping to an IP address. If the local IP address of a device is 192.168.1.100, you can ping it this way:

ping 192.168.1.100

OUTPUT:

$ ping -c 3 192.168.1.100
PING 192.168.1.100 (192.168.1.100): 56 data bytes
64 bytes from 192.168.1.100: icmp_seq=0 ttl=64 time=15.447 ms
64 bytes from 192.168.1.100: icmp_seq=1 ttl=64 time=13.156 ms
64 bytes from 192.168.1.100: icmp_seq=2 ttl=64 time=2.565 ms

--- 192.168.1.100 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 2.565/10.389/15.447/5.611 ms

After you run the ping command, the MAC address of the target will be stored in the ARP cache. ARP cache is a temporary storage that stores IP addresses and associated MAC addresses. By running the arp -a command, the MAC address-IP address combo will be listed.

$ arp -a
? (192.168.1.1) at d8:7:b6:XX:XX:XX on en0 ifscope [ethernet]
? (192.168.1.100) at 0:21:2f:XX:XX:XX on en0 ifscope [ethernet]
? (192.168.1.103) at f4:f5:d8:XX:XX:XX on en0 ifscope [ethernet]
? (192.168.1.118) at dc:3a:5e:XX:XX:XX on en0 ifscope [ethernet]
? (224.0.0.251) at 1:0:5e:XX:XX:XX on en0 ifscope permanent [ethernet]
? (239.255.255.250) at 1:0:5e:XX:XX:XX on en0 ifscope permanent [ethernet]

NOTE: For privacy reasons, the real numbers have been replaced with XX.

There is a utility called arping that discovers devices (hosts) on the network. Arping operates at the data link layer, unlike ping, which operates at network layer.

How many MAC addresses exist worldwide?

Short answer: 281 trillion.

Theoritically, the number of MAC addresses that could exist are 248 = 281,474,976,710,656, which is 281 trillion. Unless we have more than 281 trillion networked devices, we will never run out of networkable entities.

Devices do not even have to be physical. Virtual machines can get their own MAC addresses.

How to write MAC address in binary

MAC addresses are generally written in hexadecimal. If you want to convert a MAC address to binary notation, convert each hexadecimal digit to 4-bit binary using the 4-bit binary table shown above.

Example: Let us write the MAC address 00:12:34:56:78:9E in binary notation. We convert each hexadecimal digit into its 4-bit version.

Going from left to right, 0 becomes 0000, 1 becomes 0001, 2 becomes 0010, and so on. And finally, 916 becomes 10012 and E16 becomes 11102.

This is demonstrated in the table below.

0 0 1 2 3 4 5 6 7 8 9 E πŸ‘ˆ hexadecimal
0000 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1110 πŸ‘ˆ binary

Look up MAC address

To look up MAC addresses, you can visit our MAC address look up utility.

To do it manually, you have to download the text databases from the IEEE website and do a string search (ctrl+F or command+F) for the MAC address in the corresponding blocks. You will find the name of the vendor, MAC address block size and type, and the vendor's postal address, including country.

Generate MAC addresses

If you are looking to generate MAC addresses with a certain prefix, you can use our MAC address generator. This generates as many MAC addresses with a fixed prefix or OUI.

MAC Address Lookup

MAC Address Generator

Conclusion

This is just a lay person's introduction to MAC addresses and associated terminology. For more academic or detailed information, please stay tuned. You can also subscribe to our RSS feeds or email subscription.

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Published on August 31, 2022

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