Best subnetting method for CCENT?

Hi Guys. I know there are hundreds of methods for subnetting and subnetting quickly. Not being good at math, and subnetting being one of the main topics in the way of me achieving my Cisco certification, I need to know opinions on what is the best method to use on the exam.

Originally I planned to use Lammle's method, which has 5 steps (For class C networks, havent gotten to others). I can use the method fairly well if I can remember the math. For some reason i'm just not sure on it yet.

Second choice is Jeremy C's method. I havent heard of many people using it on the exam, what I have discovered is it doesnt seem in line with the type of questions encountered in exam prep. His first step is to determine the number of networs needed and convert to binary. Thats all well and good until you get a question asking what is the broadcast address for a specific network. The method doesnt appear to help with getting that answer. Or, if Cisco throws up a sim and I have to determine what the issue is, assumng I can discover its a addressing issue in the first place (Tips on this would be appreciated), how am I supposed to figure out how many networks are needed? I suppose look at the diagram and figure out how many networks are in the model...

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Comments

thinguy

Like you said there are hundreds of methods each with their own trick. But I think that really what makes it more confusing and complicated. We try out all these different methods to get the same answer and we just go in circles.
I recommend finding one of the popular methods and just sticking with it. Get it down and you're gold.
I've been using Jeremy's method from CBT.

Just my .02cents.

Souljacker

I ended up using a cross between Odom's explanation and Paul Browning's super Subnetting chart.

First I convert to binary, paying attention to the "interesting octet" according to Odom's recommendation. This allows you to realize what the question is asking you about the actual mask. So here is a question I just got from subnetting.org

What valid host range is the IP address 172.16.42.74/22 a part of?

First I would convert to binary - Class B address has two 255 octets making the interesting one the third - 8.8.6\2.8

then I just look at the super subnetting chart and count off appropriately what I need to. In this case I need 6 ticks across - we are going up in 4's so I know that 40 divided by 4 is 10 making my starting 40.1 and my ending 43.254. Subnet ID would be 40.0. Broadcast would be 43.255.

JasonIT

Like you said many ways of doing this. My advice for what its worth is to learn the binary formula. After learning how its done "correctly", I came up with short cuts that worked for me. I am sure people do this many ways that work for each one.

I always used this chart to get my magic number. This was before I had it memorized, hope it helps. This represents the CIDR to decimel notation and which magic number it correlates with.

/25---/26---/27---/28----/29----/30----/31---/32 CIDR
128---192---224---240---248---252---254---255 mask
128----64----32

1

J

SephStorm

Souljacker wrote: »

I ended up using a cross between Odom's explanation and Paul Browning's super Subnetting chart.

First I convert to binary, paying attention to the "interesting octet" according to Odom's recommendation. This allows you to realize what the question is asking you about the actual mask. So here is a question I just got from subnetting.org

What valid host range is the IP address 172.16.42.74/22 a part of?

First I would convert to binary - Class B address has two 255 octets making the interesting one the third - 8.8.6\2.8

then I just look at the super subnetting chart and count off appropriately what I need to. In this case I need 6 ticks across - we are going up in 4's so I know that 40 divided by 4 is 10 making my starting 40.1 and my ending 43.254. Subnet ID would be 40.0. Broadcast would be 43.255.

Okay, can someone explain how I would solve this question using Jeremy's method?

EDIT: You know what, I think he answers this in video 3, which I havent watched yet. Maybe i'll understand when I watch that 1.

alphagolf

I'm not sure which author has the best method but this thread made it all click into place for me: http://www.techexams.net/forums/ccna-ccent/38772-subnetting-made-easy.html

Mrock4

Not sure if it'll help, but I did a video on this. It is quite long- I should have cut it into two parts..live and learn. Hopefully it'll help:

https://www.youtube.com/watch?v=JksE5Cqc25M

At the end of the day, though, I strongly believe subnetting is something you just have to DO until it clicks...then when it does, it'll all come easy.