How fast is your subnetting?

I'd like to get a rough idea of the necessary speed needed to prepare for the CCENT ICND1 exam. For those of you who have either passed ICND1 or ICND2 recently, whats the range at which you can find the answers to the questions at subnettingquestions.com? Currently, depending on the question, I find myself resolving these problems in 45 to 60 seconds... Would you say this is sufficient? What should I get it down to? I want to make sure I have enough time for difficult sims or other things that may trip me up.

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chmorin

Monkerz wrote: »

I'd like to get a rough idea of the necessary speed needed to prepare for the CCENT ICND1 exam. For those of you who have either passed ICND1 or ICND2 recently, whats the range at which you can find the answers to the questions at subnettingquestions.com? Currently, depending on the question, I find myself resolving these problems in 45 to 60 seconds... Would you say this is sufficient? What should I get it down to? I want to make sure I have enough time for difficult sims or other things that may trip me up.

Back when I went subnetting insane I could answer most in 30 seconds to a minute depending on how much I decided to mis-read my horrible handwriting.

Now it is probably worse. But I'd say a minute would be enough. Keep in mind that you have time to jot down some tables before the exam starts to potentially double your speed with a quick reference.

jtoast

*nod* thats the first thing I do for any exam...take the scratch paper and jot down all the tables/references I anticipate needing so that I'm ready when the question comes up.

jamesleecoleman

I could do it between 3-20 seconds, depending on the problem. Make sure you compete against yourself to do better

I think that if you can get it under 25 seconds, you should be good.

Selfmade

i think Jeremy Cioara once said you should be able to answer a subnetting question in 20 seconds or less!

but yes, making a subnetting table is something a LOT of people do on that scratch paper, it only makes sense since there will be no calculator on the actual exam from what I understand.

(although I think there should be, since the calculator would only be of value in answering a subnetting question, and has no other value other than to help you calculate the answer correctly which you can do anyway on scratch paper)

chmorin

Selfmade wrote: »

(although I think there should be, since the calculator would only be of value in answering a subnetting question, and has no other value other than to help you calculate the answer correctly which you can do anyway on scratch paper)

The exam is really trying to test your understanding and ability to implement network schemes. The key word is your. The Net+ had a calculator in it, and that made me laugh since I never really needed it. In the real world, you may have a calculator. In the cisco training environment they believe that you can get better and faster by learning how to do the stuff in your head.

I can't believe I said that, I hate math AND subnetting. Give me a calculator any day!

I could do it between 3-20 seconds, depending on the problem. Make sure you compete against yourself to do better I think that if you can get it under 25 seconds, you should be good.

I just realized what subnettingquestions.com actually asks, I never used them. I had a family member give me random host numbers and created a vlsm scheme within my 30 seconds to a minute, usually about 4 or 5 different ranges. Now it is probably longer, but practice practice practice!

Devilsbane

First thing I do when I take a test is spit out any information in my head. Even if it is easy stuff, sometimes under pressure you can't think of it so its a good thing you wrote it down.

loxleynew

I can do most of them in around 10-20 seconds but I use a table I have written down to speed it up. Which is what i'll be doing on the test when I take it.

Monkerz

I appreciate everyone's input! I was told by a Net Engineer buddy of mine, "If your fiance isn't complaining about the lack of quality time you spend with her, you're not studying hard enough" I think I will take that advice and squeeze more time in as often as possible.

earweed

I take about 2 minutes but I'm not studying Cisco (yet, maybe later)
I just wanted to learn subnetting since it's part of the 70-642 studies. You guys are like ZOOM..done

fly351

I just ran through about 10 questions, averaged between 3-10 seconds on each. Do they get harder as you go on? I am going to use this site for practice tho.

@monkerz, you need to practice block size subnetting

stlsmoore

I say it takes me about 10-20 seconds for the common ones, and about 2 minutes for the wierd CIDR ones they throw at you.

Devilsbane

Monkerz wrote: »

I was told by a Net Engineer buddy of mine, "If your fiance isn't complaining about the lack of quality time you spend with her, you're not studying hard enough"

I am studying plenty then. She is always complaining.

Selfmade

Devilsbane wrote: »

I am studying plenty then. She is always complaining.

sometimes her soft comforts are better than studying

ColbyG

I can't subnet for **** anymore. I use calculators and **** sheets most of the time.

Gun to my head, I think I could manage, but it'd be tough.

Monkerz

Do they get harder as you go on?

No they do not. They are just private IP questions.

Ok, by using a **** sheet, that I can create in 2 minutes, I have narrowed the time in which I can subnet to 9 - 25 seconds depending on the question. Below is the sheet I just thought up...helps me a lot!

2^1 2
2^2 4
2^3 8
2^4 16
2^5 32
2^6 64
2^7 128
2^8 256
2^9 512
2^10 1024
2^11 2048
2^12 4096
2^13 8192
2^14 16384
2^15 32768

128....64.....32.....16.....8......4.....2.......1
128...192...224...240...248...252...254...255

Selfmade

now if someone can talk about how taking away subnet bits from the network bits to create subnets, that'd be great

Subnetting is the ONE skill that I have not reviewed on much and i'm so far behind Monkerz, I'm making him look like a CCIE

Monkerz

Taking away from network bits to make subnets? I think you are confused...

You reserve host bits to create subnets.

Say you have a Class B IP, the net mask should appear as follows:
255.255.0.0

Converted to binary and the bits identified with N as network bits and H as host bits:
11111111.11111111.00000000.00000000
NNNNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH

Say you need 50 subnets, what is 50 in binary?
110010

It takes 6 bits to make the number 50, so reserve those bits in the netmask. Identify with S, subnet bits should be turned on:
11111111.11111111.11111100.00000000
NNNNNNNN.NNNNNNNN.SSSSSSHH.HHHHHHHH

Convert back to decimal:
255.255.252.0

Easy as that...

Selfmade

Ok, I think I'm getting it, so you just find out how many bits it takes to add up to the number you need and that's how many bits you need to reserve for the subnet?

make another example but DO NOT give the answer, i will reply when I figure it out.

wbosher

If you're taking the ICND1 exam, anything under a minute is ok. If you're doing the CCNA exam, I've heard you need to be doing it in less than 30 seconds.

johnwest43

under a minute is fine for either exam.

Monkerz

Selfmade wrote: »

make another example but DO NOT give the answer, i will reply when I figure it out.

From the network 189.41.0.0/16, what would the netmask be for 43 subnets?

thenjduke

between 5 - 30 seconds. I can usually look at it and figure it out in my head where a year ago I was scared of it.

Forsaken_GA

for exam purposes, fast enough that I've never had a time issue as far as subnets go.

These days? seconds, because ipplan is sexy

Monkerz

IPPlan is cheating...

Forsaken_GA

of course it is!

but i've already passed the CCNA, so I've proven I know how to get my hands dirty. I just don't have to anymore hehe

Monkerz

Oh believe me, I can't WAIT to get my hands dirty... I just want to know everything there is to know about the exam topics, and lab myself to the moon before sitting for either exam. (ICND1 or 2)

Monkerz

I didn't want to start a new thread, so I am just going to bring this one back to life for a quick question. One of the posts, earlier in this thread, said being able to subnet in under 60 seconds will be sufficient for ICND1 and/or ICND2.

Some of my practice test questions are asking me to verify the interface addressing for up to 6 routers. I like to think I am proficient in subnetting, but these questions take a bit longer for me. After the initial brain fart, it took me 3 minutes to complete my last attempt at answering one of these.

I've thought about the actual exam, 50 questions with 90 minutes to complete, leaving me with roughly 1.8 minutes per question. Do I need to hone the skills? I am only worrying because this is my first Cisco exam, and I want to make sure I am right before clicking next, yet paying attention to the clock as well.

Selfmade

i know they suggest you be able to do it in your head, but the reality is they give you a scratch paper to take into the exam

you can make your own very uber handy (i just wanted to say uber

) subnetting chart, and it's nearly a prerequistive to jot down a subnetting chart for your exam, because it greatly reduces the mental calculations you have to do and you run a lot less of a risk that your mental calculations will be wrong. THEY DO NOT ALLOW CALCULATORS AT THE EXAM!!!

That is the main reason why one of the first things most test takers will do is jot down a subnetting and binary math chart, and before the test, they will practice using their chart, untill they can do a problem in under 20 seconds or less. That way they have more time to focus on the harder questions, like the sims and simlets

Remember, when it comes to subnetting, you'll either be right or wrong, so there's no real agonizing over your answer if you know how to do it with a chart.