Q: LAN Broadcasts

By certskills September 18, 2018 09:05

To answer some #CCNA questions, you need to think like a network analyzer (e.g., Wireshark). What values sit in the headers of an Ethernet frame or IP packet? In this next sample question, you’ll get a chance to think about the Ethernet header for a LAN broadcast.


The Question

Which answers are accurate about a LAN broadcast frame sent by host A?

A) The Source MAC is the Broadcast Address (but the Destination MAC is not)

B) The Destination MAC is the Broadcast Address (but the Source MAC is not)

C) Both the MAC Addresses are the Broadcast Address

D) The Type field is the Broadcast Type value


Figure 1: Figure Reference


Answer Post in a Few Days!

I’ll post an answer post in a few days. Watch for it! It should be the next post in chronological order as well, so watch for the link at the bottom of this page (just above the comments section).

A: Encapsulation
A: LAN Broadcasts
By certskills September 18, 2018 09:05
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  1. Null0 September 19, 07:18

    I guess

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  2. Nicholas September 19, 08:07

    B) The Destination MAC is the Broadcast Address (but the Source MAC is not)

    Reply to this comment
  3. Carlos September 19, 13:09

    The answer is B!!!

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  4. Alidoski October 24, 07:54

    B is the right one because Host A send a packet to broadcast destination to the whole devices in the same LAN,
    A is not correct becuz the source shoud not be be broadcast address they send message and that msg contain specific IP address that include source IP address but Destination can be Broadcast or Unicast also Multicast addresses depend on Topology .
    C we don’t have anything like that in networking .
    for D I didn’t understand what it mean exactly but type field it could be unicast or multicast not only broadcast .

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  5. Prathmesh Patil May 14, 11:41

    Ans is B as the Broadcast frame contrains the destination ethernet address as Broadcast address (FFFF.FFFF.FFFF) and source address as the MAC address of the device which is sending the frame.

    Reply to this comment
  6. Punya Atma March 11, 21:58

    Answer is, B.

    In the Ethernet frame, the Type field is not about broadcast or not, but, it defines the Type of protocol listed inside the frame, which is nowadays most likely, IP version 4 (IPv4) or IP version 6 (IPv6). So the choice D, is knocked off. Choices A, and, C, simply knocked off as the definition of broadcast address, is only for destination mac-address, not for source address ever.

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