Doing binary conversion without paper or a calculator...?

qsub

I'm having trouble doing binary without a piece of paper. Is this normal? Or should I be able to do it in my head?

Anyone got any tips or tricks that might be able to help?

keenon

memorize, memorize and memorize.... certain things still will require getting a pen and paper... sometime a subnet calc

qsub

So really when you see 192.. you should automatically remember that it is 11000000 in binary?

keenon

yep

Webmaster

I wholeheartedly agree, the best way to 'beat' subnetting, is to memorize the binary numbers and there corresponding common values. Also because you only need to focus on the contigious binary numbers when it comes to subnets.

I wish they drilled me with binary values back in school instead of 1x1=1, 2x1=2, 3x1-3 etc. etc

wildfire

you will find eveyone has different ways to learn, heres the way I learnt, I learned the sequence ie

0, 128, 192, 224, 240, 248, 252, 254, 255
0 1 2 3 4 5 6 7 8
I then look at a subnet mask eg 11110000 and see four 1's so I remeber four in my sequence 240. Of crouse that is only for subnetting, but subnetting is the main time you will use it.

Its probably not the best way but it helped me, and if you ask Im sure people have different suggestions.

have a look at an easy to remeber sheet here

http://www.cisco-engineer.com/new/index.php?option=com_content&task=view&id=64&Itemid=32

qsub

Yeah, I think I'm starting to get the hang of the subnetting stuff. For class C anyways.

I'm reading that CCNA book by Todd Lammle.

I started to pick it up after he does the walk through where he says "ALL YOU NEEd TO KNOW IS THESE FIVE QUESTIONS!" By the third or fourth one he gave me, I started to understand.

I haven't started the class B subnetting or Class A yet, but I'm going to assume B and A subnetting will also be in the exam?

rossonieri#1

in addition :

11100000 means bit with 1's is fixed - with 0's is variable.

counting subnets :

1110000

---

> is from left to right


counting how many hosts :

1110000

<

---

is from right to left


8 7 6 5 4 3 2 1
128 64 32 16 8 4 2 1
128 192 224 240 248 252 254 255

qsub

edit: nvm.

Jammywanks

oh I thought you meant like any number besides the typical 128, 192 pattern, I thought you mean numbers like 56 and 69 or what not LOL. In any case, for subnetting sake just start from left to right with 1's.

EdTheLad

Why memorize? Just learn the maths!
The problem with memorizing is that info will generally only be retained for a short period of time.With something like subneting which is the basis for all these cisco exams you should understand and know it well it crops up everywhere in the exams and also on the job.
Learning binary sequences is crazy and will make you crazy
Also maybe im a little crazy answering this question from a bar in Bangkok!!

qsub

I'm just curious.

In enterprise level networks. What formula is used to get subnets.

Do they do 2^(number of 1's) - 2

or

just 2^(number of 1's)

dmaftei

2^n