I HATE these practice exams

I'm at Question 29 with only 48% because of junk like this and I don't understand why I'm getting them wrong:

Question (and let me know if I'm not supposed to do this - I'll delete it if so)

Host 1 sends 3 consecutive TCP segments to Host 2 with sequence numbers 1600, 2100 and 2600 respectively. All 3 segments have a source port of 80 and a destination port of 1600. Assuming host 2 responds to acknowledge successful receipt of all 3 segments, which of the following are true?

After getting the question wrong, I went back and hit the 'show answer' to see what I got wrong. 2 the 3 I checked were correct, but the 3rd I checked was not:

The segment that is sent from Host 2 to Host 1 has an acknowledgement field of 3100.

The reasoning: Each TCP segment might be a different length. Nothing in the question states the number of bytes of data in the 3rd packet so it is impossible to know to which number Host 2's acknowledgment field has been set.

OK, except in the book (Odom's), the Ack field always was the next number in the series (IE seq 1000, seq 2000, ack will be 3000). It also specifically states "the sequence and acknowledgment fields count the number of bytes". Pages 140-141

This is FRUSTRATING and IRRITATING!

Find more posts tagged with

Free for TechExams community: Cybersecurity salary guide

Compare cert salaries and plan your next career move

Button

Comments

chmorin

You will encounter some questions like that, I remember being irritated as well. Take what you can with a grain of salt, and make sure what you used to study is more up to date than the exam you are taking.

Or, try and match how up to date the two are. No practice exam is perfect, though.

jrmeulemans

I feel your pain man. I have been studying CCENT with odom for like 4 months and still only getting like 60% on those Boson exams. They are rediculous, having stuff that is not even found in the book. I had one talking about traceroute sending icmp with a life of 1 or something like that, when the book nowhere covers that kind of thing.

bermovick

jrmeulemans wrote: »

I feel your pain man. I have been studying CCENT with odom for like 4 months and still only getting like 60% on those Boson exams. They are rediculous, having stuff that is not even found in the book. I had one talking about traceroute sending icmp with a life of 1 or something like that, when the book nowhere covers that kind of thing.

HAHA I just got that question, and of course got it wrong. Flipped open the book cause I sure don't remember reading ANYTHING about Time-To-Live in THIS book and sure enough, not a single mention of it under the 1/2 page dedicated to traceroute.

notgoing2fail

I've made it known here many times I am not a good test taker. I know how you feel.

Sometimes though, you just have to go with the flow, sometimes if you over think the question you will get it wrong, that's been my beef.

I can't tell if they are trying to trick me, or see if I'm sharp...

tha_dub

It is a bit of a trick question but they are correct in that you cannot assume the ack windows size for the next packet.

Cyanic

Whoever wrote that question is a moron.

You will find this a lot with practice tests, just be assured you will find no such nonsense on the real exam. Tough questions, yes, just not moronic ones.

Boson is notorious for asking questions about topics that are not covered in the exam. This is why many believe the Boson tests are harder then the real thing.

DevilWAH

My advice,

getting 100% in the test exams will not garantee you pass the real thing,

and getting 50% in the test will not mean you would fail the real thing.

I think I passed the CCENT with some thing like 950 while in the test exams I was only getting around 80%ish.

I would say do you understand the resoning behind both the book and the test exam explination. both are correct to an extent.

I find in this field there is a lot of learnign and then unleanring as you move higher up.

Its like at school when your are 5 you would be taught that a mushroom is a plant. Then later on you find out its nither a plant nor animal but a fungus. Then you get in to a biology degree and you find even this in not completly correct and it is more complex still.

Expct to contine like this as you move on, it is not an exact sicence and at this level lots of things are getting simplified to make them eaiser to understand.
if something like SYN requests are in the exam at this level, Cisco is going to expect you to understand the consepts of them, not have indepth knowlage about them.

Make sure you know why things are used and what function they achive with in the big picture.

note

"Host 1 sends 3 consecutive TCP segments to Host 2 with sequence numbers 1600, 2100 and 2600 respectively" this hints that segments can be different lenths as 1600, 2100 and 2600 are not constant lenths.

bermovick

*sigh*

OK, now I'm just RANTING:

In the figure, the 2960 switches have been taken out of the box and cabled, and PC2 can communicate through R1 with the rest of the IP network. However, no configuration has been added to either SW1 or SW2. As a result, the network engineers sitting at a management station to the right of R1 cannot ping or telnet to SW2. Which of the following configuration commands, when entered in the correct order on SW2, allow the network engineer to ping or telnet to SW2 from the management station.

PC2 --- SW2 ---- R1

*
(there's more to the network, but I've only shown the parts that apply to the question).

I got this wrong, selecting options 'interface vlan 1' and 'ip address <the address listed for S2), because I did NOT also select "ip default-gateway (routers lan-side IP address) and 'no shutdown', despite the question clearly stating that PC2 can communicate through R1 with the rest of the IP network! Clearly the statement in bold means that 1) the port is not administratively down, and 2) a default gateway has already been entered, no?

Forsaken_GA

bermovick wrote: »

I got this wrong, selecting options 'interface vlan 1' and 'ip address <the address listed for S2), because I did NOT also select "ip default-gateway (routers lan-side IP address) and 'no shutdown', despite the question clearly stating that PC2 can communicate through R1 with the rest of the IP network! Clearly the statement in bold means that 1) the port is not administratively down, and 2) a default gateway has already been entered, no?

No, actually, you're wrong on this one. Just because the switch is passing traffic at layer 2 doesn't mean it can communicate at layer 3. If you want to be able to talk to a layer 2 switch over layer 3, it needs to be configured like any other host - ip, subnet, and default gateway, and the interface has to be up. Forgetting to issue no shut on the interface is a big big gotcha

bermovick

Forsaken_GA wrote: »

No, actually, you're wrong on this one. Just because the switch is passing traffic at layer 2 doesn't mean it can communicate at layer 3. If you want to be able to talk to a layer 2 switch over layer 3, it needs to be configured like any other host - ip, subnet, and default gateway, and the interface has to be up. Forgetting to issue no shut on the interface is a big big gotcha

I still don't get it. For the switch to be operating (passing data between PC2 and router), the interfaces in use have to be up, so there should be no need for a 'no shutdown'.

I'm not 100% sure about the default gateway; I'll have to check that on my switch here real quick (hums Jeopardy music)

Yup, I just ran 'no ip default-gateway' on my switch and disconnected, and I can still telnet into it just fine.

xenodamus

bermovick wrote: »

I still don't get it. For the switch to be operating (passing data between PC2 and router), the interfaces in use have to be up, so there should be no need for a 'no shutdown'.

You aren't talking about a physical interface here, though. "interface vlan 1" is the management interface. It's not a physical port on the switch (which all work out of the box - this is what you're referring to).

Like forsaken said, the management interface has to be configured just like any other host. To manage the switch from a PC on the OTHER side of the router, the switch has to know what its default gateway is.

I assume you're testing this with your PC and the switch on the same LAN segment.

alan2308

bermovick wrote: »

I still don't get it. For the switch to be operating (passing data between PC2 and router), the interfaces in use have to be up, so there should be no need for a 'no shutdown'.

I'm not 100% sure about the default gateway; I'll have to check that on my switch here real quick (hums Jeopardy music)

Yup, I just ran 'no ip default-gateway' on my switch and disconnected, and I can still telnet into it just fine.

You're telnetting into it from a device connected directly to it? If that's the case, then you don't need a default gateway because the switch and PC are on the same network. You need a default gateway when the two devices are on different networks. Set it up like this:

SW1

PC1

And try to telnet into the switch without a gateway set on the switch. The PC will be able to send packets to the switch, but the switch will not be able to send anything back.

xenodamus beat me while I was still typing away.

bermovick

Yeah, I understand the need for a default gateway for the 'return path', so to speak, but in this example the PC was on the same subnet as the switch.

I understand what's being said about VLAN1 being a 'virtual port' so the fact that the physical ports are up is irrelevant. I don't remember having to 'no shutdown' when setting up for telnet/SSH access, but that could be possible. I'll have to power up switch #2 and check.

wbosher

DevilWAH wrote: »

My advice,

getting 100% in the test exams will not garantee you pass the real thing,

and getting 50% in the test will not mean you would fail the real thing.

I think I passed the CCENT with some thing like 950 while in the test exams I was only getting around 80%ish. [/I]

I agree. When I did CCENT, I got terrible marks on the Boson exam but passed the real thing (can't remember the exact percentages). I think there may have been some questions on the ICDN1 test exam that were really from ICND2 curriculum.

Don't panic.

Aldur

bermovick wrote: »

Yeah, I understand the need for a default gateway for the 'return path', so to speak, but in this example the PC was on the same subnet as the switch.

Sounds like the question was about a PC/management station that wasn't on the same subnet as the switch.

bermovick wrote: »

... the network engineers sitting at a management station to the right of R1 cannot ping or telnet to SW2. Which of the following configuration commands, when entered in the correct order on SW2, allow the network engineer to ping or telnet to SW2 from the management station.

bermovick

Hmm, not sure how I missed that, and that's a good point - except PC2 can communicate through R1 with the rest of the IP network., suggesting a default gateway already exists.

Ahh, it's irrelevant now anyways, I got to around question 110 with 48% or so and just gave up haha.

[edit] duh nevermind; PC2 would have the gateway. SW1 still needs it for itself.

Aldur

no worries mate, it's all a big learning process for all of us

Just keep your chin up and keep studying

dairou18

The Boson test was VERY annoying and made me doubt myself until I started asking questions on this forum. When you go through the test, make sure you read the explanations on the questions you get wrong. It also doesn't hurt to read the explanations on the questions you got right. For me this test was very intimidating at first but I learned a lot from it and I realized I had more to study.

Forsaken_GA

bermovick wrote: »

Yeah, I understand the need for a default gateway for the 'return path', so to speak, but in this example the PC was on the same subnet as the switch.

Look at the question and the diagram again.

The question said a network admin to the right of R1 is trying to ping SW2. That means he's on a different subnet, going through R1 to get to SW2. That means SW2 needs a default gateway to complete that ping, otherwise it has no return path.

The devil is in the details.

Forsaken_GA

bermovick wrote: »

Hmm, not sure how I missed that, and that's a good point - except PC2 can communicate through R1 with the rest of the IP network., suggesting a default gateway already exists.

A default gateway is set on PC2. PC2 knows how to get to R1 via layer 3. SW2 is providing the layer 2 connectivity between the devices. SW2 isn't doing any routing, so whether or not it has a default gateway is irrelevant to whether or not PC2 can ping the rest of the network. Traffic from PC2 to R1 is switched through SW2 (layer 2 communication). From R1 on, it's all layer 3 communication.

You need to go back and familiarize yourself with how traffic moves at layer 2 and layer 3. This is a fundamental concept you need to understand.

bermovick

I'd realized what I was missing (see my [edit] above). For some reason I was thinking that PC2 being able to go through the router meant there was connectivity all the way through/along the pipe. Yeah I felt pretty dumb when I realized that

I have a pretty good grasp of that; I just always seem to miss some tiny (but vitally important) piece of information when I read a question or think through to the solution. *sigh*