Having problems subnetting in my head.

Raymond Mason

Hello! I have been studying for my CCENT for quiet a while now; I believe I am on month 5? Its taking so long because I keep going backwards in the book trying to soak everything in. Anyways, I know it is expected to do subnetting in your head but I am finding that really really hard to do. I read tons of tutorials even the ones on this forum but I still find it extremely difficult. I think it stems from not being able to multiply and do divisions in my head and keeping track of all the numbers without getting lost. I don't have a real problem with anything else it is just subnetting that is giving me trouble.

Thanks for reading.

koz24

Have you read Chapter 4 in Todd Lammle's book? I think I tried every way of subnetting when I was studying for the CCENT and found his method the fastest. Check it out if you haven't already.

Jon_Cisco

All I can suggest is memorizing the block sizes and working with Subnetting Practice Questions practice tests daily.
I also used cisco binary game app which is free to download and will help you learn binary.

james43026

Personally I find the magic number method of subnetting to be the quickest, here is a tutorial for it.

Madmd5

+1 for Todd's book. I just read Chapter 4 today and I found his method very useful and easy to comprehend. I didn't have a clue how to subnet before today.

Deathmage

Jon_Cisco wrote: »

All I can suggest is memorizing the block sizes and working with Subnetting Practice Questions practice tests daily.
I also used cisco binary game app which is free to download and will help you learn binary.

+1 for block size, and custom subnets or CIDR's for the subnets. Understanding how to count out subnet/hosts like subnets are from left to right and hosts are from right to level in powers of 2. Once you know the powers you just remember the block sizes and it make it so much easier.

Took me well over 10 months to finally figure out subnetting, so be patient, eventually it clicks, just whatever you do don't give up!

mikeybinec

BLOCK SIZES BLOCK SIZES BLOCK SIZES!!! Block sizes are the same no mater what octet you're in.

OK, time for another mikey replay courtesy of the Deathmage thread:


Cmon man.. just do the block sizes!! OK, here we go:

Test question comming up!!


Given the IP address 20.188.13.50 /12, what is the network ID and two valid hosts?

A) 20.192.0.1

20.177.255.255

C) 20.190.1.255

D) 20.255.255.255

E) 20.176.0.0


READY!!! START THE CLOCK!!

A slash 12 means it hits the 2nd octet and has a block size of 16. How many 16s can we fit under the 188 WITHOUT GOING OVER? 11!11 11 times 16 = 176

WE GOT OUR NETWORK ID 20.176.0.0 /12

Our first host is 20.176.0.1

add a block of 15 to the 176 to come to the end of our network and you have 20.191 Now put in the host addreses in the third and 4th octet 255.254 for the last host and 255.255 for the broadcast address

Last host address is 20.191.255.254

Bcast address is 20.191.255.255

MIKEY DID IT 30 SECONDS OR LESS

=====================================

So your network range runs from 20.176.0.1 - 20.191.255.254

You might get confused on my sentence when I say "add a block of 15 to the network id" If you added sixteen, you would
be at the beginning of the next network.. basically the block sizes are even in the sense that you use the numerals 0-15 or 0-3 or ________________ (pick your block size) Remember, network ID;s (an analogy would be the name of the club or gang you belong to) is ALWAYS EVEN NUMBERED i.e 192.168.1.0 172.16.1.32 etc etc The broadcast ID is always ODD (the manager of your apartment complex who talks to everybody-- a mikey analogy)

Regards

Raymond Mason

Have you read Chapter 4 in Todd Lammle's book?

I don't have Todd's book I have Wendells book. Thank you guys for the suggestions and I am going to try them all out to see how it goes for me.