# Stupid question for the day - 70-291

Discussion in 'MCSE' started by LMC, Oct 29, 2008.

1. ### LMCGuest

So here I am asking another stupid question regarding 70-291 (and perparing
myself to take a punch in the face from MCPGP)...

I'm sure there will be questions regarding subnetting and such ... all fine
and good. I'm just curious if the exam provides the most basic calculator
(the native calc program) so I don't have to waste time counting on my
fingers and toes.

LMC, Oct 29, 2008

2. ### FrisbeeĀ®Guest

http://www.learntosubnet.com

FrisbeeĀ®, Oct 29, 2008

3. ### LMFGuest

I'm pretty sure the calculator is the complete windows one. Scientific and
all. But i wouldn't know for sure since i can do all the in my head

LMF, Oct 29, 2008
4. ### CBICGuest

You can't subnet in your head? You're sh!tting me! Can you dress yourself in
the morning? It's not hard just remember /28 is block size of 16 and go from
there.

CBIC, Oct 29, 2008
5. ### Victor AsuquoGuest

The test environment provides a basic calculator without the scientific
function. That is more than enough to sail you through. As a tip, do know
you ip addressing and subnetting very well. I flunked this exam at first try
and if you as me, that was the culprit.

Best of luck anyway

Victor Asuquo, Oct 31, 2008
6. ### DieHard

Joined:
Oct 29, 2008
Messages:
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The way I subnet: Takes around 30 seconds (if that) - with practice!

I have seen some stupid subnetting questions and thought I'd offer they way I do it to try and help.

Before you try and learn how to subnet you need to learn binary and the different classes of addresses.

Forget magic numbers and special tables, if you know binary it's easy, trust me.

191.16.97.150 with a mask of 255.255.255.192

Prefix notion:255.255.255.192 = /26

In the mask you always ignore the 255 and the 0 part so we use the 192 part( 4th octet )in the mask and the address.

192 in binary is
128 64 32 16 8 4 2 1
1 1 0 0 0 0 0 0

What ever the last one is in the mask 64 in this case, this is the number the subnet go up by:

Network number: 0 range: 0-62 BC Address: 63
Network number: 64 range: 65-126 BC Address: 127
Network number 128 range: 129-190 BC Address: 191
Network number 192 range: 193-254 BC Address: 255
Network number 256 (not valid as greater than 255)

Therefore as 192 in the mask is the 4th octet we use the 4th octet in the address: 150

From the above find what number is below 150, 150 is between 128 and 192 therefore:

191.16.97.150 /26

Network number 191.16.97.128 /26
range: 191.16.97.129 - 191.16.97.190