In Ethernet networking, what is the standard bit length of a MAC address and how is it usually written for human readability?

Introduction / Context:
Media Access Control (MAC) addresses are used at the Data Link layer to uniquely identify network interface cards on Ethernet and other Layer 2 technologies. For Cisco exams, you must know both the bit length and the typical textual representation of a MAC address.

Given Data / Assumptions:

• The question asks about both the bit length and the expression form of a MAC address.
• We are talking about the standard Ethernet MAC address format defined by IEEE 802.
• We want the common way MAC addresses are written for humans, not internal binary representation.

Concept / Approach:
A standard Ethernet MAC address is 48 bits long. Internally, it is just a 48 bit binary value, but for readability it is shown as 12 hexadecimal digits, grouped into six octets. Each octet is written as two hexadecimal digits, and these octets are typically separated by colons, hyphens, or dots depending on vendor style. Example formats include 00:1A:2B:3C:4D:5E or 001A.2B3C.4D5E.

Step-by-Step Solution:
Step 1: Recall that each hexadecimal digit represents four bits.Step 2: A six octet MAC address has 6 * 8 = 48 bits. This corresponds to 12 hexadecimal digits because 48 / 4 = 12.Step 3: For human readability, the 12 hex digits are grouped into six pairs; each pair corresponds to one octet, often separated by colons (:) or hyphens (-).Step 4: An example is 00:1A:2B:3C:4D:5E, where each pair like 00 or 1A is a value from 00 to FF in hexadecimal.

Verification / Alternative check:
On real network devices, commands such as show interfaces or ipconfig /all display MAC addresses in one of these standard formats. You will see 48 bit addresses expressed as six hex pairs, confirming the format described in option A.

Why Other Options Are Wrong:
Option B describes a 32 bit dotted decimal format, which actually matches IPv4 addresses, not MAC addresses.Option C suggests a 64 bit format like IPv6, but this is not how classic MAC addresses are represented, even though they can be related to IPv6 interface identifiers.Option D gives only 16 bits, which is far too short to uniquely identify interfaces at global scale.

Common Pitfalls:
Some learners confuse MAC address length with IP address length or with IPv6 interface identifiers derived from MAC addresses. Remember that MAC addresses are 48 bits, while IPv4 addresses are 32 bits and IPv6 addresses are 128 bits.

Final Answer:
The correct description is that a MAC address is 48 bits, written as six pairs of hexadecimal digits separated by colons or hyphens, for example 00:1A:2B:3C:4D:5E.