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Home > Archive > alt.certification.cisco > April 2003 > Just passed BSCI, But one question I Didn't Understand, Any explanation??
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Just passed BSCI, But one question I Didn't Understand, Any explanation??
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| CRock 2003-04-22, 10:24 am |
| Today is April 22nd 2003 and I passed the BSCI exam with a score of
860 out of 700, I think that is fair if you consider the fact that I
didn't practice on real router , I just had to imagine the
configuration, and just read them in the study material that I had...
But there was a question That I didn't understand in the test, maybe
this will be a spoil for the exam but one question didn't hurt anyone
,,,it was:
Given the summarized network address 175.17.100.0/22
how many C class subnets were summarized..
A. 2
B. 4
C. 8
D. 16
E. 32
First of all this isn't a class C address even if IP classless routing
is in place it doesn't matter is it a class C or B.., so what's the
deal here
Can anyone offer me any explanation about this question... I know I
passed But I want to know the answer for peace of mind.
Thank you...
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| 4 total class C addresses. 175.17.100.0 /24
175.17.101.0/24
175.17.102.0/24
175.17.103.0/24
Course, I could be wrong...
"CRock" <mirtoni@yahoo.com> wrote in message
news:c879c05f.0304220635.246c55ac@posting.google.com...
> Today is April 22nd 2003 and I passed the BSCI exam with a score of
> 860 out of 700, I think that is fair if you consider the fact that I
> didn't practice on real router , I just had to imagine the
> configuration, and just read them in the study material that I had...
>
> But there was a question That I didn't understand in the test, maybe
> this will be a spoil for the exam but one question didn't hurt anyone
> ,,,it was:
>
> Given the summarized network address 175.17.100.0/22
> how many C class subnets were summarized..
>
> A. 2
> B. 4
> C. 8
> D. 16
> E. 32
>
> First of all this isn't a class C address even if IP classless routing
> is in place it doesn't matter is it a class C or B.., so what's the
> deal here
>
> Can anyone offer me any explanation about this question... I know I
> passed But I want to know the answer for peace of mind.
>
> Thank you...
| |
| anchor40 2003-04-22, 11:40 am |
| Nope, you're dead on. I guess the writer of that particular question fell into the "Class C" mask mix-up. A case of listen to what they mean, not what they say! 
anchor40 | |
| anchor40 2003-04-22, 11:45 am |
| By the way, CRock, congratulations!
 | |
| Stuart Robinson 2003-04-22, 12:24 pm |
| > 4 total class C addresses. 175.17.100.0 /24
> 175.17.101.0/24
> 175.17.102.0/24
> 175.17.103.0/24
How can those be Class C addresses, 175 is in the Class B range is it not
?
Stuart.
| |
| anchor40 2003-04-22, 1:21 pm |
| How often have you heard 255.255.255.0 refered as a "Class C mask" instead of a "whack-24" or "24-bit mask???"
Too many times to count!!!
| |
| vladimir 2003-04-22, 1:24 pm |
|
"CRock" <mirtoni@yahoo.com> wrote in message
news:c879c05f.0304220635.246c55ac@posting.google.com...
> Today is April 22nd 2003 and I passed the BSCI exam with a score of
> 860 out of 700, I think that is fair if you consider the fact that I
> didn't practice on real router , I just had to imagine the
> configuration, and just read them in the study material that I had...
>
> But there was a question That I didn't understand in the test, maybe
> this will be a spoil for the exam but one question didn't hurt anyone
> ,,,it was:
>
> Given the summarized network address 175.17.100.0/22
> how many C class subnets were summarized..
>
> A. 2
> B. 4
> C. 8
> D. 16
> E. 32
>
> First of all this isn't a class C address even if IP classless routing
> is in place it doesn't matter is it a class C or B.., so what's the
> deal here
>
> Can anyone offer me any explanation about this question... I know I
> passed But I want to know the answer for peace of mind.
>
> Thank you...
That's a B class address so original subnet mask is 16. Given that here IP
address is summarized with 22 subnet mask you have to add 6 subnests and an
easy way to calculate the number of summarized address is like this
2^(22-16)-2 =
2^6 -2=32-2-30 So you have 30 summarized addresses. where 22 is summarized
subnet mask , 16 is class B subnet mask and 2 is network and broadcast
address.
| |
|
| IP Address : 175.17.100.0
Address Class : Classless /22
Network Address : 175.17.100.0
Subnet Address : 175.17.100.0
Subnet Mask : 255.255.252.0
Subnet bit mask : nnnnnnnn.nnnnnnnn.nnnnnnhh.hhhhhhhh
Subnet Bits : 22
Host Bits : 10
Possible Number of Subnets : 1
Hosts per Subnet : 1022
Selected Subnet : 175.17.100.0/255.255.252.0
Usable Addresses : 1022
Host range : 175.17.100.1 to 175.17.103.254
Broadcast : 175.17.103.255
Strict classfull C networks always have a 24 bit mask you can cidr it down
to more networks but when asked assume 24 bit networks on tests. so how
many 24 bit networks to the question is 4.
"anchor40" <anchor40.mas0b@mail.examnotes.net> wrote in message
news:anchor40.mas0b@mail.examnotes.net...
> Nope, you're dead on. I guess the writer of that particular question
> fell into the "Class C" mask mix-up. A case of listen to what they
> mean, not what they say!
>
> anchor40
> ---
> View this thread: http://www.examnotes.net/article1007731.html
> anchor40 - Networking
Phreak----------------------------------------------------------------------
--
> anchor40's Profile:
http://www.examnotes.net/forums/mem...o&userid=158211
>
| |
|
| "Stuart Robinson" <Stuartr@nospam.please> wrote in message
news:memo.20030422173344.1084A@srnet.compulink.co.uk...
> > 4 total class C addresses. 175.17.100.0 /24
> > 175.17.101.0/24
> > 175.17.102.0/24
> > 175.17.103.0/24
>
>
> How can those be Class C addresses, 175 is in the Class B range is it not
> ?
>
> Stuart.
Variable Length Subnet Masks and Classeless Interdomain Routing allow for
Route Summarization. Say for instance your network is 175.17.0.0/16. This
gives you from 175.17.0.0 through 175.17.255.255 to use. Well, instead of
using all of those host addresses with a 16-bit mask, you want to subnet
your branch offices which have no more that 100 people at any given
location. So, you use the 175.17.100.0/24 subnet for your Austin TX
location, the 175.17.101.0/24 subnet for the Dallas location and the
175.17.102 for San Antonio. All of these connect back to the Houston branch
175.17.103.0 /24 via a frame relay network. The Houston location acts as a
hub for the Texas branches and is connected back to the corp. HQ in NY City
via a T3 or the like. So on the NY City router to Houston, you route
traffic for those four networks as 175.17.100.0/22 instead of putting a
separate route for each one to the same destination. This is where
hierarchal addressing comes in handy.
| |
| Stuart Robinson 2003-04-23, 2:24 am |
| Thanks for the explanation.
I understand the summarised\classless bit but how can 175.17.100.0 contain
any Class C networks since its obviously a Class B address ?
I could sort of understand if the question asked "how many C class size
subnets were summarised"
Stuart.
| |
| anchor40 2003-04-23, 10:44 am |
| Don't worry, you're right on. Ever feel like you're a pebble in a raging river trying to stop the river?
Again, they are making the "industry-wide" mistake that a 255.255.255.0 (/24) subnet mask equals a Class C network. It drives me batty!!!!! I guess I'm just a semantic freak!
Address "Classes" were developed by ARIN, and the advent of VLSM to further optimize the IP address allocation process created this monster.
The two have nothing to do with each other - technically - but because of the prevalence of companies being assigned Class C addresses for use, the association of the x.y.z.0/24 address naming convention, the /24 mask has unfortunately become identified a Class C network.
Thus a 4.176.97.0/24, a 175.100.0.0/24 and a 199.34.69.0/24 have unfortunately been called "Class C" networks because of the mask. They should be called 24-bit networks, or Class A,B or C networks with a Class C mask. But only 199.34.69.0/24 can really be called a Class C network.
Likewise, a 199.0.0.0/8 is not a Class A network, right? My point is that we as an industry need to stop refering to networks by the "Classes" that ARIN has assigned to the ranges of IP addresses.
I am that pebble, trying to change the way the industry looks at network naming, one drop at a time... | |
| Dean B. Johnson 2003-04-23, 11:24 pm |
| After reading the question and reading all of the responses I must be
missing something...
The test listed a class B address...
Wanted to know how many subnets "were" summarized based on the /22 mask
But worded it wrong when they classified the resulting subnets as class
"C"....
So I see it as a misleading "typo" on the test ....
No ???
p.s
Congrats on passing...
"CRock" <mirtoni@yahoo.com> wrote in message
news:c879c05f.0304220635.246c55ac@posting.google.com...
> Today is April 22nd 2003 and I passed the BSCI exam with a score of
> 860 out of 700, I think that is fair if you consider the fact that I
> didn't practice on real router , I just had to imagine the
> configuration, and just read them in the study material that I had...
>
> But there was a question That I didn't understand in the test, maybe
> this will be a spoil for the exam but one question didn't hurt anyone
> ,,,it was:
>
> Given the summarized network address 175.17.100.0/22
> how many C class subnets were summarized..
>
> A. 2
> B. 4
> C. 8
> D. 16
> E. 32
>
> First of all this isn't a class C address even if IP classless routing
> is in place it doesn't matter is it a class C or B.., so what's the
> deal here
>
> Can anyone offer me any explanation about this question... I know I
> passed But I want to know the answer for peace of mind.
>
> Thank you...
| |
| sikdogg 2003-04-28, 1:24 pm |
| "vladimir" <nospam@nospam.com> wrote in message news:<P4fpa.100242$BQi.8097@news04.bloor.is.net.cable.rogers.com>...
> "CRock" <mirtoni@yahoo.com> wrote in message
> news:c879c05f.0304220635.246c55ac@posting.google.com...
> > Today is April 22nd 2003 and I passed the BSCI exam with a score of
> > 860 out of 700, I think that is fair if you consider the fact that I
> > didn't practice on real router , I just had to imagine the
> > configuration, and just read them in the study material that I had...
> >
> > But there was a question That I didn't understand in the test, maybe
> > this will be a spoil for the exam but one question didn't hurt anyone
> > ,,,it was:
> >
> > Given the summarized network address 175.17.100.0/22
> > how many C class subnets were summarized..
> >
> > A. 2
> > B. 4
> > C. 8
> > D. 16
> > E. 32
> >
> > First of all this isn't a class C address even if IP classless routing
> > is in place it doesn't matter is it a class C or B.., so what's the
> > deal here
> >
> > Can anyone offer me any explanation about this question... I know I
> > passed But I want to know the answer for peace of mind.
> >
> > Thank you...
>
> That's a B class address so original subnet mask is 16. Given that here IP
> address is summarized with 22 subnet mask you have to add 6 subnests and an
> easy way to calculate the number of summarized address is like this
> 2^(22-16)-2 =
> 2^6 -2=32-2-30 So you have 30 summarized addresses. where 22 is summarized
> subnet mask , 16 is class B subnet mask and 2 is network and broadcast
> address.
A /22 mask will summarize 4 class C subnets. It doesn't matter if you
start with a class A or B address. They gave you a class B address to
confuse the situation and make you think.
| |
| Hansang Bae 2003-04-28, 10:24 pm |
| [snip]
> > > Given the summarized network address 175.17.100.0/22
> > > how many C class subnets were summarized..
In article <b9f38793.0304280946.1039eb3b@posting.google.com>,
sikdogg@yahoo.com says...
> A /22 mask will summarize 4 class C subnets. It doesn't matter if you
> start with a class A or B address. They gave you a class B address to
> confuse the situation and make you think.
It's incorrectly worded. You can get X number of /24's, but you can't
get a "class C" address from a range that belongs in "B". It's
semantics, but it's important to note the distinction.
Of course, in the real world...CIDR pretty much made CLASSful addresses
a thing of the past.
--
hsb
"Somehow I imagined this experience would be more rewarding" Calvin
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| |
|
| Is the total 900?
860 out of 900 sounds right..
On 28 Apr 2003 10:46:55 -0700, sikdogg@yahoo.com (sikdogg) wrote:
>"vladimir" <nospam@nospam.com> wrote in message news:<P4fpa.100242$BQi.8097@news04.bloor.is.net.cable.rogers.com>...
>> "CRock" <mirtoni@yahoo.com> wrote in message
>> news:c879c05f.0304220635.246c55ac@posting.google.com...
>> > Today is April 22nd 2003 and I passed the BSCI exam with a score of
>> > 860 out of 700, I think that is fair if you consider the fact that I
>> > didn't practice on real router , I just had to imagine the
>> > configuration, and just read them in the study material that I had...
>> >
>> > But there was a question That I didn't understand in the test, maybe
>> > this will be a spoil for the exam but one question didn't hurt anyone
>> > ,,,it was:
>> >
>> > Given the summarized network address 175.17.100.0/22
>> > how many C class subnets were summarized..
>> >
>> > A. 2
>> > B. 4
>> > C. 8
>> > D. 16
>> > E. 32
>> >
>> > First of all this isn't a class C address even if IP classless routing
>> > is in place it doesn't matter is it a class C or B.., so what's the
>> > deal here
>> >
>> > Can anyone offer me any explanation about this question... I know I
>> > passed But I want to know the answer for peace of mind.
>> >
>> > Thank you...
>>
>> That's a B class address so original subnet mask is 16. Given that here IP
>> address is summarized with 22 subnet mask you have to add 6 subnests and an
>> easy way to calculate the number of summarized address is like this
>> 2^(22-16)-2 =
>> 2^6 -2=32-2-30 So you have 30 summarized addresses. where 22 is summarized
>> subnet mask , 16 is class B subnet mask and 2 is network and broadcast
>> address.
>
>A /22 mask will summarize 4 class C subnets. It doesn't matter if you
>start with a class A or B address. They gave you a class B address to
>confuse the situation and make you think.
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