Subnetting by hand...

charliepaul

This is funny, I just spent a couple days an a certain chapter in a a network plus book and all the while was stressing out, the chapter was on subnetting and how to do them by hand. About half way into it I started thinking of the poll thats on this website about the hardest topic for everyone that is studying for the Network+ exam being the OSI model, and thought to myself omg, how come I don't see this at the top of the list? I have a pretty good grasp of it now and it was a little easier than I thought it was, once I got the steps down. And I'm glad I understand it now. But after about 2 days stressing about it at the end of the chapter I read this...

"This section has introduced you to the concept of subnetting. Don’t worry too much about it for the exam, because CompTIA focuses more on class addressing than subnetting. So make sure you are familiar with identifying the class addresses and then, if you can, get an understanding of subnetting—it will only help".


OMG LOL Does anyone know if future cert exams place a big emphasis on subnetting by hand? Like the CCNA?

dynamik

charliepaul wrote:

OMG LOL Does anyone know if future cert exams place a big emphasis on subnetting by hand? Like the CCNA?

Yes. 291 in the MCSA/MCSE track does as well. Just learn to do it in your head. It's not a big deal

Daniel333

It never goes away. Even at work... and I'll I do is application administration.

phantasm

I practiced subnetting until i could do it in my head.

This is a table i memorized which helps:

/25 = block size of 128 = 126 usbale IP's
/26 = block size of 64 = 62 usable IP's
/27 = block size of 32 = 30 usable IP's
/28 = block size of 16 = 14 usbale IP's
/29 = block size of 8 = 6 usable IP's
/30 = block size of 4 = 2 usable IP's (WAN links)

Of course this assuming that the router is utilizing the all 0's subnet.

Pumpkinhead

Heh,
That is kind of funny to me. My instructor spent a whole class on sub-netting by hand. He had 2 large white boards that the class sub-netted across.

Afterwards he said that we didn't need to know this for the test, "just be familar with the sub-net classes (A,B,C)".

He said that was a "real world" instructor. He did not want to teach to the test exclusively.

I had the same reaction you did.

Kikode

My instructor was great at teaching this in college. Made total sense and I was a whiz at doing it in class. Eh to bad my memory sucks though hehe. Thanks m8 now I gotta go brush up on subnetting again

Slowhand

If you're planning on doing MCSA/MCSE, you'll need to know subnetting for the infrastructure exams (70-291 and 70-293). If you're planning on doing the Cisco path, you'll need to learn subnetting in-depth, as you'll be tested on it explicitly for the CCNA test(s), and be expected to implicitly know it for any future exams. If you're looking to work in the networking field, it'll be a very useful skill to be able to calculate subnets in your head, and stopping to fire up the ol' SolarWinds calculator isn't always an option when you're in the field or out in a wiring closet/data center. For the Network+ exam, however, I think your book is very much right and you'll only need to worry about the first three classes, and only have a very general understanding of subnets.