CCNA Exam: Flow of a packet

Posted on 2009-04-24
Last Modified: 2012-06-21

1) This is related to a prep test for CCNA Exam.
2) Please see the graphic at the attachment.
3)The question: "When a packet is sent from Host 1 to Server 1, in many different frames will the packet be encapsulated as it is sent across the internetwork?"
4) The given answer: Two
5) My question: i) Why two? and what are they?, ii) If possible, please give or tell the detailed Flow of the packet from "Host 1" and arriving at "Server 1"
6) Thank you

Question by:tjie
    LVL 50

    Assisted Solution

    by:Don Johnston
    The correct answer if three.

    Every time a router receives a packet, the layer 2 header (and trailer) is stripped off and new layer 2 information is created for the next hop.
    LVL 26

    Assisted Solution

    donjohnston -

    Not to be pedantic, but since there's two routers wouldn't it be two? The first 'hop' is actually into a switch - that doesn't re-encapsulate the packet.
    LVL 10

    Assisted Solution

    Midnight -

    Don is right.

    Your encapsulation path would be -

    First - Host 1 to R1 - Host 1 encapsulates, R1 receives and strips.
    Second - R1 to R2 - R1 re-encapsulates sends to R2, strips
    Third - R2 to Server 1 - R2 re-encapsulates, sends to Server 1, strips


    Author Comment

    - so the Prep Test is Wrong?
    - The right answer is 3?
    LVL 7

    Accepted Solution

    If the question asks how many times a packet will be encapsulated during traveling to server tha answer is 3
    But if it asks how many encapsulation types will be used the answer is two, ethernet and hdlc or ppp.
    I am teaching ccna since 2002 and believe me there test (testking, pass4sure) hava enough mistakes!!!

    Author Comment

    - I agree with Hau
    - Don, Midnight and Atlas: any other comments before i close it? I will wait up to tomorow (around 8 hours)
    - Thank you very much for all of you

    LVL 26

    Expert Comment

    No objections at all. He explained it well.

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