At 07:08 PM 9/19/00, Phil Barker wrote:
>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,
Why should we assume that? The question doesn't assume that. Also, it's
pretty clear that the question is about who retransmits the original frame,
not who retransmits the frame that collided with it. The answer is
obviously the router. This is fundamental Ethernet 101 stuff. It's so
basic, we should move this question to the CCNA list! %-)
Priscilla
>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
> >
> > **NOTE: New CCNA/CCDA List has been formed. For more
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>
>
>____________________________________________________________
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
**NOTE: New CCNA/CCDA List has been formed. For more information go to
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