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Member Posts: 33 ■■□□□□□□□□
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Which of the following is an example of a valid subnet mask?

255.255.225.0
255.255.191.0
255.255.127.0
255.255.64.0
None of the above is a valid subnet mask

I selected the first option and it tells me that none of them is a valid answer.

Does anyone know the reason why ?

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Registered Users Posts: 4 ■□□□□□□□□□
Quick and dirty answer is that a subnet mask has to be all 1's from left to right in binary before you get to any 0's.
Meaning you cannot have any 1's to the right of a zero.
for example 255.255.225.0 = 11111111.11111111.11100001.0000000
255.255.191.0= 11111111.11111111.101111111.00000000
255.255.127.0= 11111111.11111111.01111111.0
255.255.64.0= 11111111.11111111.01000000.0

Seeing it spelled out like this, we see that none of them work as a subnet mask.
Subnetting always easier when converted to binary.
Hope this helps.
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Member Posts: 33 ■■□□□□□□□□
Quick and dirty answer is that a subnet mask has to be all 1's from left to right in binary before you get to any 0's.
Meaning you cannot have any 1's to the right of a zero.
for example 255.255.225.0 = 11111111.11111111.11100001.0000000
255.255.191.0= 11111111.11111111.101111111.00000000
255.255.127.0= 11111111.11111111.01111111.0
255.255.64.0= 11111111.11111111.01000000.0

Seeing it spelled out like this, we see that none of them work as a subnet mask.
Subnetting always easier when converted to binary.
Hope this helps.

hey madgarin thanks for your help....my 801 exam is on 14th and stressed out a bit..lets see how it goes
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Registered Users Posts: 4 ■□□□□□□□□□
No worries. I am also taking the 801 on the 14th in the evening. Never underestimate the power of positivity. Remember as I tell my kids, the studying is truly the difficult part.
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Member Posts: 33 ■■□□□□□□□□
thats so true ! well, i booked my exam in the morning at 11:30am.
anyways, wish you all the luck on your exam!!
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Member Posts: 33 ■■□□□□□□□□
I just passed the 801 exam and am sooo happy
i scored 779 not that high but i am grateful im done with it !

People out there who are looking for exam prep material, i would highly recommend the EXAM CRAM sixth edition by David Prowse
This is the ONLY material i used for passing this exam. I did watch some professor messer videos but not all of them though.
Make sure you guys take the test which is at the back of the exam cram book and also definitely do all the 801 quizzes on examcompass site, like other people are recommending. Actual exam questions are very similar to above mentioned materials.

I got two performance and three simulation based questions as well. I had a very little knowledge about computers prior taking this exam. So, if i can pass, you guys can certainly pass it. Just study hard and don't worry...
good luck to all of you folks who are indenting on taking this exam !! i'll start my prep for 802 from tomorrow...
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Registered Users Posts: 4 ■□□□□□□□□□
Nice job. I passed as well with a 832. I believe I over prepped a bit. I used the Mike Meyers book and his practice tests. I have been working on computers since I was 15, so I do have practical experience which helps a bit. Now to continue the quest for more certs to prove it.
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Member Posts: 33 ■■□□□□□□□□
way to goooooo !! many congratulations
good luck on 802