How many bytes are used for the 'Source' field in an Ethernet header?

The 'Source' field in an Ethernet header is 6 bytes long. This field contains the MAC (Media Access Control) address of the device that is sending the Ethernet frame. A MAC address is a unique identifier assigned to network interfaces for communications at the data link layer of a network. It is standardized to be 48 bits long, which translates to 6 bytes, with each byte represented as two hexadecimal digits.

Having a 6-byte source address allows for a sufficiently large pool of unique addresses, ensuring that devices on the same network segment can be uniquely identified. This is critical for the proper functioning of Ethernet networks, allowing frames to reach the correct destination based on the addresses provided in the header.

In contrast, the incorrect options represent values that do not align with the standard size of a MAC address. For example, a 4-byte address would not provide enough unique identifiers for the number of devices commonly found on even a small network, and 2-byte or 8-byte sizes do not fit Ethernet specifications for MAC addresses.