In Ethernet networking, how many bits are there in a standard MAC address?

Introduction / Context:
On Ethernet and many other local area network technologies, each network interface is identified at the data link layer by a MAC address. This address is used for local delivery of frames on the same network segment. Knowing the size of a standard MAC address is basic networking knowledge and is often tested in certification and university exams.

Given Data / Assumptions:

• The focus is on traditional IEEE 802 MAC addresses used in Ethernet.
• These addresses are typically written as six pairs of hexadecimal digits.
• Each hexadecimal digit represents four bits.
• The question asks for the total number of bits in a MAC address.

Concept / Approach:
A standard MAC address has six bytes, which is 48 bits. In human readable form, it is often written as six hexadecimal octets separated by colons or hyphens, for example 00:1A:2B:3C:4D:5E. Each hexadecimal digit corresponds to four bits, so each pair of hexadecimal digits is one byte or eight bits. Six of these bytes give a total of 48 bits. This fixed length and globally unique assignment scheme help ensure that each physical interface has a distinct address on the network.

Step-by-Step Solution:
Step 1: Observe that a MAC address is usually shown as six pairs of hexadecimal digits, such as AA:BB:CC:DD:EE:FF.Step 2: Recall that each hexadecimal digit represents four bits.Step 3: Each pair of hexadecimal digits is one byte, which equals eight bits.Step 4: Multiply six bytes by 8 bits per byte to obtain 48 bits.Step 5: Conclude that a standard MAC address contains 48 bits in total.

Verification / Alternative check:
IEEE 802 standards specify 48 bit MAC addresses for most Ethernet and wireless LAN interfaces. Documentation on organizationally unique identifiers describes how the first 24 bits identify the vendor, while the remaining 24 bits identify the specific interface. Tools such as ipconfig, ifconfig, or network interface configuration panels display MAC addresses in the six octet format, further confirming the six byte, 48 bit length.

Why Other Options Are Wrong:
Option A, 64 bits, describes extended address spaces used in some newer schemes but is not the standard size for traditional MAC addresses. Option C, 32 bits, would yield only four bytes, which is too short to provide the globally unique address space that Ethernet requires. Option D, 16 bits, corresponds to only two bytes and is far too small for MAC addressing in modern networks.

Common Pitfalls:
Confusion sometimes arises because IPv6 uses 128 bit addresses and can derive interface identifiers from MAC addresses using modified formats. However, the underlying hardware MAC address is still 48 bits in most Ethernet devices. Another pitfall is to count the visible hexadecimal characters without converting them correctly into bits. Remembering the six byte structure or the 24 bit plus 24 bit vendor and device split makes it easier to remember the 48 bit total.

Final Answer:
A standard Ethernet MAC address is 48 bits long.