Venting

THA_DOC

Subnetting is an Evil Brain twister. Whomever the geniune was who created subnetting was EVIL Person. I hate Subnetting 500 different formulas to come a simple answer that a computer on calculator in a matter of second. The monster who puting subnetting on test in which the testor already nervous should beater to a pulse.... I HATE Subnetting

ciscoman2012

Well you better get to love it because that's what networking is all about! :P

But seriously, it's not so hard once you've grasped the fundamentals. Now....until you get to the point where you fully understand it learning subnetting will be very painful. I was honestly about to stop studying for my ICND1 because I wasn't able to convert decimal numbers into binary.

Now I just laugh at myself for even thinking that and am glad I pushed through. I'm sure you will do the same!

spicy ahi

Agree with ciscoman. It's like anything else, keep practicing and soon enough it'll become second nature. Plus you'll definitely need it for further cisco certifications so if that's your plan, I'd take the time to get subnetting down cold. Have you gone to subnettingquestions.com? I went to the site for two weeks straight answering questions for about 30mins. to an hour each day and after two weeks I could "do the math" without having to draw out the binary. Give it a try!

reloaded

Haha, I understood your pain...until Jeremy from CBTNuggets showed me the light. It's ALL about block size!! (i.e. subnet mask bit position = block).

boredgamelad

We did two weeks (six 3 hour classes) of subnetting in my Intro to Networking class in college. By the end, everyone in class was a subnetting master.

Then, I took the Cisco Discovery/Exploration courses. The instructor spent about 3 days on subnetting, and everyone who hadn't already taken the Intro to Networking class was lost for most of the semester. We ended up having to teach our group mates how to subnet during lab time.

It really is a frustrating process, and everyone always says "you'll get it eventually", because they were once in your position. You WILL get it eventually, and when you do, you will wonder what other people are talking about when they say it's so hard to understand. Just stick with it!

martell1000

i guess it is so hard for a lot of people because of the binary calculation.

a good hint is to print out a subnet table and use it everyday. after a few weeks you will just KNOW that a .248 mask is a /29 and has 8-2 usable hosts in it ....

THA_DOC

I have reading testing and studying subnetting for a while. I first encouter it in MSCA courses, it was difficult then. However Microsoft did not use go to the degree of asking how many host when on Variable Lengths. I have understand Jeremy's 3 step formula.
1. Determine the number of networks and convert to binary.
2.Reserve bits in the subnet Mask and Find the Increment.
3.Use the Increment to find the Network Range.

Example: Network 195.5.20.0 Needs 50 netowrks
1. 50 = 00110010 or 6 bits
2. 255.255.255.00000011 or 255.255.255.252 /30 with an increment of 4
3. Ranges 195.5.20.0_______195.5.20.3
195.5.20.4_______195.5.20.7
195.5.20.8_______195.5.20.11
195.5.20.12______195.5.20.15
195.5.20.20______195.5.20.23 etc Simple


Example: 192.168.10.0= Network Address; 255.255.255.128=subnet mask. Therefore

1. How many subnets? 5 since 128 is 1 on (10000000), 2(2)- 2=126
2. What are the valid subnets? 256-128= 128 so our subnets are 0, 128
3. What are the broadcast address of each subnet 0 ,127
4. what are the valid hosts? 0 and 128

Subnet: 0 128
First host: 1 129
Last Host: 126 254I Broadcast 127 255 Understandable with a little work and can follow it through to some simple varable length.

But having to know all of this:
Subnet Mask CIDR Values
255.0.0.0 /8
255.128.0.0 /9
255.192.0.0 /10
255.224.0.0 /11
255.240.0.0 /12
255.248.0.0 /13
255.252.0.0 /14
255/254.0.0 /15
255.255.0.0 /16
255.255.128.0 /17
255.255.192.0 /18
255.255.224.0 /19
255.255.240.0 /20
255.255.248.0 /21
255.255.252.0 /22
255.255.254.0 /23
255.255.255.0 /24
255.255.255.128 /25
255.255.255.192 /26
255.255.255.224 /27
255.255.255.240 /28
255.255.255.248 /29
255.255.255.252 /30
And have plug it in every IP address on 90 minute test make not want to take the test. Oh , then after calculating the the ip addresses configure the switches and routers too..... AHHHHH

mella060

Seriously, all it takes is about 2-3 weeks of solid practice. Forget about the subnetting used in the microsoft courses, i had no clue either until i started my CCNA studies.

My suggestion would be to pick up a copy of Todd Lammles CCNA study guide if you haven't already done so and go through the chapter on subnetting. Thats how i got started with it all. At first i had no idea but after a few weeks of going through all the exercises again and again, it 'clicked'.

The key is when starting is to write EVERYTHING down, bit by bit. Grab a notebook and write everything down, the question, everything. That way it sticks in your brain. Spend half an hour to an hour each day just on subnetting and doing the exercises from the book. Rinse. Repeat. Rinse Repeat.

Know your subnet formulas...2^n for networks/subnets and 2^n-2 for hosts where n is the number of bits used

Know your powers of 2.

In your example network 195.5.20.0 needs 50 networks or subnets

What power of two will give you 50 subnets ?

2^4 = 16
2^5 = 32
2^6 = 64

195.5.20.0 is a class c address with a default subnet mask of 255.255.255.0 or in binary 11111111.11111111.11111111.00000000
So you will need to borrow 6 bits from the host portion of the address

So your subnet mask will be 255.255.255.252 or in binary 11111111.11111111.11111111.11111100

jdancer

What he said.

If you know your powers of two, then use your fingers to figure out the block size. It's that simple.

ChickenNuggetz

That's exactly what I do! Thank the gods I have at least 8 fingers!

In all seriousness, I found Jeremy's explanation in the CBT Nuggets series to be really straightforward. Even with those, it still took some time (and practice) for it to really soak in. I kept on doing subnettingquestions.com questions for practice. If I got the answer wrong, I wouldnt move on until I figured out why I got it wrong. After about a solid weekend of doing this for a few hours each day, I could subnet within a minute!

Moral of story: doesnt matter how "bad" you think you are; with ENOUGH practice, you'll get it. Practice really does make perfect!!!

djfunz

Yeah, subnetting took me a couple months to really get down. Mind you, I didn't spend much time on it per day. A few questions from subnettingquestions.com per day and Jeremy Cioara's method was enough for me. I remember taking half a sheet of paper and 10 minutes just to solve one question. Then I was able to eventually do them in my head in under 15 seconds. You'll get there. If you want to get into networking, you'll have to master it though. It only gets more complicated from there if you don't have the basics down. VLAN, VLSM, and Summarization along with wildcard masks are all based on being able to subnet. Keep plugging away. You'll look back and wonder what was so hard.

Futura

can i just say that to me Subnetting is like the screens on the Matrix,

Once you see it, you can't unsee it.

I used to stand in the shower and recite 8x 16x 32x 64x tables.

Subnet license plates and various number on bill board whilst driving

and now, I laugh to myself.

cb3dwa

i must say i never thought i would understand it but now it just comes natural

i think if i can do it anyone could,

keep at it and you will get there

Monkerz

If you dislike IPv4 subnetting, you might as well change your goal to something other than networking. IPv6 subnetting (coming slowly) will completely blow your mind and make you want to beat someone.

THA_DOC

Thanks everyone for the advice. I guess will subnetting this weekend, all weekend. I'll start with basic and Yes I have Lammle Study Guide. Funny thing is I can understand Block size fairly well. I guess I just need to go more in depth with the subnetting and the power of 2^n-2.
I appreciate everything.

SharkDiver

I agree with Futura.
Once you see it, you can't unsee it.
Someone says /29 mask to me and my mind just jumps to 32 groups of 8 with 6 hosts each.

Plus, you have to love a good Matrix reference.
BUT, it takes skill to use a Matrix Reloaded reference.

"Damn it Morpheus, not everyone believes what you believe!"
"My beliefs do not require them to."

xbuzz

SharkDiver wrote: »

"Damn it Morpheus, not everyone believes what you believe!"
"My beliefs do not require them to."

I knew you posted here Jeremy!