is mac address changed when being routed?

Discussion in 'Cisco' started by jh3ang, Aug 27, 2006.

  1. jh3ang

    jh3ang Guest

    Hello ~: i have a confusing concept problem that i need help !!
    there are two switches, and those are connected to Router A.
    and please look at this following facts:
    switch A has connection to host A.
    switch B has connection to host B.

    Like this:
    host B
    |
    Router A __Switch B
    |
    switch A __host A


    My question is "What will be the source mac address of the frames that
    hostA receives from hostB?"

    I answered this question as "The Mac address of router interface.", but
    the correct answer was "The Mac address of hostB mac address.."!!!!

    How come..?
    I hope this question has wrong answer itself !!!
    jh3ang, Aug 27, 2006
    #1
    1. Advertising

  2. In article <>,
    "jh3ang" <> wrote:

    > Hello ~: i have a confusing concept problem that i need help !!
    > there are two switches, and those are connected to Router A.
    > and please look at this following facts:
    > switch A has connection to host A.
    > switch B has connection to host B.
    >
    > Like this:
    > host B
    > |
    > Router A __Switch B
    > |
    > switch A __host A
    >
    >
    > My question is "What will be the source mac address of the frames that
    > hostA receives from hostB?"
    >
    > I answered this question as "The Mac address of router interface.", but
    > the correct answer was "The Mac address of hostB mac address.."!!!!
    >
    > How come..?
    > I hope this question has wrong answer itself !!!


    You were correct. MAC addresses pass through switches, but not through
    routers.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***
    Barry Margolin, Aug 27, 2006
    #2
    1. Advertising

  3. jh3ang

    Phil Schuman Guest

    "Barry Margolin" <> wrote in message
    news:...
    > In article <>,
    > "jh3ang" <> wrote:
    >
    > > Hello ~: i have a confusing concept problem that i need help !!
    > > there are two switches, and those are connected to Router A.
    > > and please look at this following facts:
    > > switch A has connection to host A.
    > > switch B has connection to host B.
    > >
    > > Like this:
    > > host B
    > > |
    > > Router A __Switch B
    > > |
    > > switch A __host A
    > >
    > >
    > > My question is "What will be the source mac address of the frames

    that
    > > hostA receives from hostB?"
    > >
    > > I answered this question as "The Mac address of router interface.",

    but
    > > the correct answer was "The Mac address of hostB mac address.."!!!!
    > >
    > > How come..?
    > > I hope this question has wrong answer itself !!!

    >
    > You were correct. MAC addresses pass through switches, but not

    through
    > routers.
    >

    it's hard to tell from the textual diagram,
    but the key is how the switches are connected to each other,
    and to the router - ??

    ie - if they all are on the same ethernet and can "see" each other
    directly,
    then the MAC would just go across from one switch to another.

    However - if the switches are connected to TWO interfaces on the router,
    then the frames would have to pass THRU the router MAC interfaces.

    Also - even if they all are on the same physical segment,
    if the "transmission" is using a routed protocol like TCP/IP between two
    subnets
    on the same general infrastructure, then the router again would have to
    route
    the packets, and the Ethernet frames would have the router MAC address.
    Phil Schuman, Aug 27, 2006
    #3
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. John

    Routed port on 3550 switch

    John, Jan 31, 2004, in forum: Cisco
    Replies:
    1
    Views:
    3,698
    Steinar Haug
    Jan 31, 2004
  2. Richard Antony Burton

    NAT & routed at the same time, on an 837

    Richard Antony Burton, Dec 1, 2004, in forum: Cisco
    Replies:
    7
    Views:
    3,157
    Richard Antony Burton
    Dec 3, 2004
  3. Victor Tan

    Routed port mode

    Victor Tan, Dec 3, 2004, in forum: Cisco
    Replies:
    0
    Views:
    1,825
    Victor Tan
    Dec 3, 2004
  4. Replies:
    3
    Views:
    14,772
    JF Mezei
    Mar 7, 2007
  5. ttripp
    Replies:
    5
    Views:
    2,220
    Thrill5
    Feb 5, 2010
Loading...

Share This Page