Cisco CCNA Exam: Layer 2 Ethernet Frame

Layer 2 Ethernet Frame

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What are contained in layer 2 Ethernet frame? (Choose three.)



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A. B. C. D. E.


The Ethernet protocol is used for communication between devices on a local area network (LAN). Ethernet protocol is organized into various layers, where the Layer 2 Ethernet frame provides the data-link layer functionality, which enables data to be sent and received over the physical layer.

The Layer 2 Ethernet frame contains the following components:

  1. Preamble: It's a 7-byte field used to synchronize the receiver's clock to the sender's clock, and it is used to identify the beginning of a frame. The preamble is composed of alternating 1s and 0s followed by an ending 1 bit.

  2. Destination MAC Address: A 6-byte field that specifies the Media Access Control (MAC) address of the device for which the frame is intended. The destination MAC address is used by the receiving device to identify whether the frame is for it.

  3. Source MAC Address: A 6-byte field that specifies the MAC address of the device that sent the frame. The source MAC address is used by the receiving device to send a response to the sender.

  4. Type/Length: A 2-byte field that specifies the type of the protocol used in the data field of the frame or the length of the data field.

  5. Data Field: This field carries the actual data being transmitted between the devices. The length of this field varies, and it can be between 46 and 1500 bytes.

  6. Frame Check Sequence (FCS): A 4-byte field that is used to check the integrity of the frame during transmission. The FCS is generated by the sender and verified by the receiver.

Therefore, from the given options, the three components that are contained in Layer 2 Ethernet frame are Preamble, Type/Length, and Frame Check Sequence.

Note that the TTL and version options are not part of the Layer 2 Ethernet frame, but rather the IP header of a Layer 3 packet.