Having trouble learning subnetting

Can someone point me to a good place to learn to do the subnetting questions? I just can't seem to learn to do this, I've been trying for 3 weeks and I still miss almost ever question when I do the practice exams. So far the study book I've been using is the Sybex book by Lammle. I've looked at a few websites about subnetting but still nothing is clicking.

Thanks in advance.

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Comments

Webmaster

Well, I guess nothing beats www.learntosubnet.com

jkelly

Thanks, I've looked at that site, but I can't seem to make it work on my machine. I only have a 24k connect to the net so video just isn't very workable. I guess I'll have to send him the money for the CD.

loksenna

I don't know where to go for subnetting, but I will help you if you want. I haven't passed the exam, but I know subnetting like the back of my hand. Its the only thing I do well.

jkelly

Thanks for the offer, loksenna!

I think It's slowly starting to click. A large part of my problem may have been that I've had a difficult time concentrating due to headaches that I couldn't seem to get rid of. Finally was prescribed an allergy medication that helped with that greatly. It's amazing how much better I can think now! I'm still not good at subnetting, but at least I'm understanding my mistakes now, so I guess I'll keep practicing! Hopefully this is going to get easier now. Back to the books!

Thanks again!

loksenna

ahhh, I understand your situation completely. It's always such a relief when something like that gets fixed. I'm glad for you.

jkelly

I'm catching onto this now, but I wonder how I'll ever be able to answer these in less than a minute. I'm terrible at math, so trying to find multiples of 4,8,16, etc, is killing me.. I was hoping to take the 640-607 test before it is discontinued in September, but I may just have to do the new one. I wonder if I need new study guides...

loksenna

Hmm, I dunno about which test to take. Go ahead and just memorize everything up to, say, 12 binary digits.
Here's my method, try this:
Take out a sheet of paper, and write down 8 blanks with a period. Then write down 3 more of the same thing. Under each blank in the last octave, write the decimal value of each placeholder (backwards: 128,64,32,16,8,4,2,1). Try and visualize the octave. Then try and visualize the whole ip address. Use that to help you learn the numbers.

Like this

##### etc. etc.

Here is my method for subnetting with speed. Say they give you an address with a /# format mask.
Like this:
192.168.1.32/27
Now, write down an 8 for the first octave and then a period, since you know that is a full octave for the network part of the address. Then write an 8 and a period for the second octave. Then do that for the third octave. Now stop, since you know that covers up to the third octave, which is /24. For the last octave you know that 3 digits are used for the subnet since 27-24 is 3, which leaves 5 for the host address. I write it like this

8.8.8.3/5

Sorry to be long-winded, but that is part of my method and I am really fast with subnetting, I just wanted to offer that to you.