CCNA practice question

[vorgusa]

Ok, I am doing some practice questions for my CCNA test tomorrow and I rain accross a question dealing with CSMA/CD and it asked me to pick 3. One of the ones I picked was "Networks are segmented into multiple collision domains using bridges for CSMA/CD networks." Another question they had that I got right used a picture with multiple bridges separating the network into multiple collision domains (not using the term CSMA/CD)...

Are one of these questions wrong since they seem to contradict each other, or is there a difference between CSMA/CD and Collision Domains.. is the CSMA not part of a bridge?

 

[spidey07]

A "segment" is considered a collision domain. A collision domain exists at layer1 because it deals with the electrical signals on the wire.

Bridges do indeed separate collision domains because they operate at layer2, separating the segments into different segments/collision domains. Switches are also layer2 devices so each port on a switch (really a switch is a multi-port bridge) is a single collision domain.

It's important to understand all this but I will also say that collisions are a thing of the past as all ethernet LANs operate in full duplex now so it's impossible for a collision to even occur unless a hub is used.

CSMA/CD is the physical layer means ethernet uses to send frames. It senses carrier and detects collisions. This is all physical layer stuff.

 

[vorgusa]

so you would say that the answer "Networks are segmented into multiple collision domains using bridges for CSMA/CD networks." is correct even though the question says it is wrong?

 

[spidey07]

That is a fuzzy statement. You can't really use a bridge to make a single CSMA/CD network. A segment IS a single CSMA/CD network and a bridge separates them.

It could go eitherway depending on the other choices.

 

[vorgusa]

yeah I get that a lot on these questions... really frustrates me when I see stuff like that. I am looking at the cisco practice questions now, and according to them 127.16.71.43 is a private IP range and 10.215.34.43 is not.... how am I supposed to study well for this when I keep finding stuff like this!... getting a little frustrated

 

[bigpow]

CSMA/CD -> collision domain -> backoff algorithm for multiple devices (+hub) in one network segment
one switch port/interface = 1 collision domain = 1 network segment
a switch has as many collision domain as its number of ports/interfaces - but only one broadcast domain

 

[drebo]

When I took my CCNA test, there were absolutely no questions that specifically had to do with half duplex network operation, and that included the few questions I got about wifi. I was kind of disappointed.

 

[Jamsan]

So did you pass your exam?

 

[drebo]

I did, actually.

 

[ch33zw1z]

congrats, Cisco makes those tests a real PITB

 

[Jamsan]

Originally posted by: drebo
I did, actually.

Sorry, I meant the op.

 

[vorgusa]

Yep! by a small margin.. and down to the last minute. The longest question of the test for me was the second to last question.... was not good timing

 

[drebo]

When I took it, all of my simulation questions were in the first 10 questions. So when I finally got done with those and looked at the clock, the first 10 questions had taken me almost a half hour. I freaked out, thinking the entire test would be that way and I'd run out of time for sure, although the test really only took me about 50 minutes to do.

 

[mcmilljb]

Yeah, they really push you on time. I just wish they would break the exam into 2 sections. One part for the simulations and one part for the non simulation questions. Then you don't have to cram in so much in a short amount of time, and you can allow people to go back to previous questions. I hate not being able to review questions but normally not enough time to even do that at the end of the exam.

 

[spidey07]

Originally posted by: mcmilljb
Yeah, they really push you on time. I just wish they would break the exam into 2 sections. One part for the simulations and one part for the non simulation questions. Then you don't have to cram in so much in a short amount of time, and you can allow people to go back to previous questions. I hate not being able to review questions but normally not enough time to even do that at the end of the exam.

On the job you don't have time or the ability to go back and redo your decisions.

 

[mcmilljb]

Originally posted by: spidey07

Originally posted by: mcmilljb
Yeah, they really push you on time. I just wish they would break the exam into 2 sections. One part for the simulations and one part for the non simulation questions. Then you don't have to cram in so much in a short amount of time, and you can allow people to go back to previous questions. I hate not being able to review questions but normally not enough time to even do that at the end of the exam.

On the job you don't have time or the ability to go back and redo your decisions.

You also don't have to drag and drop ip address boxes on the screen.

So if you make a mistake on the job, you can't go back to fix it? I could have sworn I could...

I'm talking about being able to go back and look over my answer choices on non simulation questions. There is a reason they have it in their current format. They don't want people skipping to the simulation parts to look up an answer. If you separate the two sections, you make sure people have plenty of time to not worry about the simulation questions and no one is looking up an answer. It's a testing format, and it's quite normal to check yourself during a test.