Took 37 question ICND1 test and...

smcclenaghan

I was surprised at some of the questions which seem to conflict with the 640-822 ICND1 Cert Guide, but I'm hoping I've just misunderstood and someone could guide me.

One question:


What will happen if a collision occurs in an Ethernet... Wrong


A. One of the stations data transmission will fail.
B. Both stations wil send out a warning on the network before they retransmit the data.
C. A Transport layer protocol such as UDP or TCP will request a retransmission of the data.
D. Both stations will retransmit the data after a random wait time created by a backoff algorithm.



I'm sure I read that any system that notices a collision will send a jamming signal. Actually, p66, step 4 of the ICND1 Cisco Cert guide says:
"If a collision occurs, the devices that had been sending a frame each send a jamming signal to ensure that all stations recognize the collision."
Are we splitting hairs on the definition of "warning" here? God I hope not or I'm doomed to fail this thing.


Another one:



Which of the following is true concerning an IP address?... Wrong


A. IP addressing is defined at Layer 3 of the OSI model.
B. The host portion and the network portion are always of equal length.
C. The host portion can be all zero bits.
D. The network portion of a Class C address is 3 bytes.


Aren't we splitting hairs again here? A *valid* IP address can't have a host portion of all zeroes. If the ICND1 asks me if 0.0.0.0 is an IP address am I supposed to say yes?


Please, I'd love any feedback on these two. And I'm sorry if this has been asked a jillion times and I just missed it.

bbarrick

I think you have to take the wording literally. The word "warning" isn't technically correct since it sends out a jamming signal and not a warning. D is correct in that they will randomly send the data again after the collision to avoid another collision. I don't remember read the words "backoff algorithm" though which would have thrown me off as well. I could see why you chose the answer you did, I think it's worded to be a little tricky.

On the second question this might help:

Host address - Wikipedia, the free encyclopedia

Souljacker

In both cases I think they are trying to determine two things:

1. Do you understand the full spectrum of how CSMA\CD works
2. Do you understand how to convert the masks between decimal and binary

In the case of number one, the best answer to describe how CSMA\CD works is that the devices' transmissions collide, they each set a random wait timer and then listen so they can try again. Therefore the best answer is D.

In the second case, they want to know do you understand that in the case of 192.168.1.0/24 it is masked actually 8.8.8.0 in binary bits? In this case, the host portion is always all 0 binary bits. There would be no such host 0.0.0.0 as there is no such mask as 0.0.0.0. you are thinking that a valid mask cannot have a subnet portion of all 0's. But a valid host is always all 0's in the binary mask.

I am also taking my ICND1 soon. I wish you and I both good luck!

smcclenaghan

Souljacker wrote: »

In both cases I think they are trying to determine two things:

1. Do you understand the full spectrum of how CSMA\CD works
2. Do you understand how to convert the masks between decimal and binary

In the case of number one, the best answer to describe how CSMA\CD works is that the devices' transmissions collide, they each set a random wait timer and then listen so they can try again. Therefore the best answer is D.

In the second case, they want to know do you understand that in the case of 192.168.1.0/24 it is masked actually 8.8.8.0 in binary bits? In this case, the host portion is always all 0 binary bits. There would be no such host 0.0.0.0 as there is no such mask as 0.0.0.0. you are thinking that a valid mask cannot have a subnet portion of all 0's. But a valid host is always all 0's in the binary mask.

I am also taking my ICND1 soon. I wish you and I both good luck!

I see what you're saying, but frankly, it isn't possible to get into the questioner's head to determine if B or D is right. B omits the algorithm, D omits the jamming signal.

I'll just have to hope I don't see too many questions like that.

I really appreciate the feedback, folks.

Souljacker

Technically, they both omit the specific verbiage "jam signal". I agree with bbarick - that's really the only clue as to why the answer was marked wrong in that case, making the "more complete" answer the one with the backoff timer.

Although I agree, the use of the word "algorithm" is... misleading. Bad question. I hope I don't see something like that on the test either.