Fields found in an IEEE Ethernet frame header: Which of the following fields are included in the Ethernet frame header (not the payload) as defined by IEEE framing?

Introduction / Context:
An IEEE 802.3 Ethernet frame consists of a header, payload, and trailer. Knowing which fields live in the header versus payload or trailer is essential for interpreting captures and understanding frame processing by NICs and switches.

Given Data / Assumptions:

• Field 1: Source and destination MAC address.
• Field 2: Source and destination network address (IP addresses).
• Field 3: Combination of MAC and network addresses (not a real header field).
• Field 4: FCS field.

Concept / Approach:

The Ethernet header includes Destination MAC, Source MAC, and a Length/Type field (and optional 802.1Q tag). IP addresses are part of the Layer 3 packet, not the Layer 2 header. The Frame Check Sequence (FCS) is a trailer used for error detection. Among the provided groupings, the best correct selection that references actual Ethernet control fields and excludes IP addresses is the pairing of MAC addressing (1) and the FCS integrity field (4) found in the frame structure (header+trailer).

Step-by-Step Solution:

Verification / Alternative check:

Refer to Ethernet frame format diagrams: Preamble/SFD (not part of the MAC header proper), Destination MAC, Source MAC, Length/Type, optional tag, payload, and FCS trailer.

Why Other Options Are Wrong:

“2 only” and “2 and 3 only” include IP addresses, which are not in the Ethernet header.

“3 only” is not an actual field definition.

Common Pitfalls:

Equating frame header with entire frame; confusing Layer 2 MAC addressing with Layer 3 IP addressing; overlooking that FCS is a trailer, not header, though it is a defined field of the frame structure.

Final Answer:

1 and 4