Sub Netting

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So is Sub Netting some dark black magical thing everyone is telling me about.
Or is there as simple way to learn it, apart from using a sub net calculator?

 

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Yes its a dark black magical thing, but hopefully, these should show you the light...

http://www.learntosubnet.com
http://www.subnetting-secrets.com/
http://www.subnettingquestions.com/default_uk.asp

 

I would also suggest Subnet Tutor from innovative Software Concepts. Inexpensive and I use it daily to refresh my skills.

Subnetting is the biggest hurdle to face for the CCNA. Plenty of other things to learn as well, but without Subnetting you can forget it.

Good luck!!!!!

 

Confirmed. Be able to subnet in your head before attempting the CCNA. You'll be glad you did... plus, you'll never escape from subnetting. Learn it the right way now, and you'll never forget it later.

 

Subnetting looks very intimidating at first glance. But once you've mastered it, you've mastered it. Takes some doing, but it's doable. My advice is to use those links provided by Mr Cheeks, especially the one about subneting secrets. Afterwards you'll wonder what all the fuss was all about.

 

Cheers for that.

 

Yeah, in our academy class, we did at least 15 minutes at the beginning of EVERY lesson in going over subnetting. A bit tedious when I understood it right at the start. After a while, you develop a way to easily think it all up in your brain. When I now see /28, 14 usable hosts and subnet increments of 16 instantly appear in my head.

You'll get that last sentence in a while, don't worry

 

To understand slash notation I would sit down and really learn how the binary math behind subnetting works.

You don't have to remember it or be able to do it but if you understand the underlying theory then I find it really helps to appreciate *why* a /28 gives you x number of subnets and y number of hosts.

As for a quick and easy tip, say your octet in question is 240; I would subtract that from 256 (as for WHY it's 256, think binary - all the 1s are on) to give me a total of 16 - my block size. Ditto for an octet of 192, what with 256-192 giving a block size of 64.

Once you have something that works for you then practice, practice and practice some more and learn to count in 16's - you will need to!

 

I checked that out and that actually works pretty good.

 

Can't for the life of me remember where I got it from, but I believe it may have been the Sybex book.

And as an aside, once you have identified your block size, just multiply it until you find the subnet address and you have a piece of cake way of getting the subnet address, the broadcast address and then the range for useable hosts.

Saves me loads of time when revising subnetting.

 

Yeah, this is the method I use too. I identify the block sizes differently though.