I havn't read this thread so apologies if this has
been done already.
Computer 1 sends to Computer 2.
Router B relays a valid frame to computer 2.
Assume no other devices on Segment B for clarity,
computer 2 must be transmitting a frame on this
segment in order for the collision to occur.
Therefore router B and computer 2 do a random back-off
before attempting to re-transmit. So shouldn't the
answer to which device re-transmits be "either"
depending on which device can respond the fastest ?
i.e Router B's frame is totally independent from
Computer 2's frame.
Regards,
Phil.
PS : hope thats not a real CCIE question or I think
I'll be throwing tantrums on the day .......
--- Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote:
> Where did these questions come from? Please specify
> the source (book, etc.)
> so that we know we aren't disobeying the NDA and
> giving you answers from an
> actual test. These sure sound like questions from
> the CCIE written. Also, I
> think it would be best to limit each e-mail message
> to one topic. It makes
> discussions easier to follow.
>
> Despite all that, I can't resist giving you my
> answers! &;-) See below.
>
> At 05:18 AM 9/17/00, Derek Chung wrote:
> >Question 1:
> >Router A and Router B are configured to route IP to
> each other over a serial
> >line. Host A is connected to Router A and Host B is
> connected to Router B. A
> >packet is sent from Host A to host B. A hit on the
> serial line causes an
> >error in the packet. Retransmission is sent by:
>
> Host A retransmits the packet. The data-link layer
> protocols in use today
> on serial lines, including PPP, Frame Relay, and
> Cisco HDLC, detect errors
> but are not responsible for error correction or
> retransmission.
>
>
> >Question 2:
> >During the middle of a TCP conversion across a
> routed backbone, the network
> >receives a voltage spike and several of the packets
> are damaged. Where are
> >the packets retransmitted from?
>
> The TCP sender. This is almost a repeat of the last
> question.
>
>
> >Question 3:
> >Computer1 --------[Segment
>
>A]-------RouterA--------------RouterB----------[SegmentB]--------------Compu
> >ter2
> >A packet is sent to Computer 2 from Computer 1. A
> collision occurs on
> >Segment B. Which device will retransmit the frame
> and what will the source
> >MAC address be (when the packet actually reaches
> Segment B)?
>
> Router B senses the collision and retransmits at the
> MAC layer. The MAC
> address is Router B's Ethernet address.
>
>
> >Question 4:
> >When computer A sends a frame to computer B across
> many routers, how will
> >the source and destination layer 3 addresses
> change? How will the source and
> >destination layer 2 addresses change?
>
> Layer 3 addresses won't change (unless you have NAT
> or tunnelling or
> something else bizarre.) The Layer 2 addresses
> change each time a router
> re-encapsulates the packet in a data-link-layer
> header than includes
> layer-2 addresses.
>
> Priscilla
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
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