Getting back into CCENT

Raymond Mason

Hello! I have been studying for the CCENT for a quiet a long time in the past. I really just gave up because the subnetting was just really too much for me. I could learn everything else just fine, but I really, really couldn't do subnetting in my head. I had a difficult time just doing it on paper.

I also got discouraged because other people can learn CCENT in a month, while it took me 2+ years to learn the bulk of it. So today, I decided I am not going to let subnetting get in the way of getting my certification. Spending 2+ years and 100$+ plus dollars on equipment is just too much just to give up on.

Since I spent so much time on it, I can get back into it really easily since everything else is going to be a refresher. I really need to spend my time studying subnetting heavily. I need to take subnetting a little bit at a time. I read many threads on subnetting on here, but there is still something about it that is difficult.

I know I can do subnetting because I solved a problem successfully once.

dontstop

Are you subnetting using the Binary or Decimal method? If you're using the Binary method you should really look at using the Decimal method.

Raymond Mason

dontstop wrote: »

Are you subnetting using the Binary or Decimal method? If you're using the Binary method you should really look at using the Decimal method.

I believe I used the binary method, I can try it but I doubt its going to be much easier. I am just going to try and illustrate it while going through it like this for example:

From cisco.com

"The bit just to the left of that holds a value of 2^1"

I assume they mean this:

dontstop

Yep the binary method is the one in which you list out IP Addresses and Subnet Masks as long strings of binary numbers. It's too much effort to do in the exam and the decimal system makes the process a lot quicker and easier.

I personally floundered around with Cisco certifications for many years. After I learnt the decimal method for Subnetting which took around 10 days (multiple different sources) it clicked. It was literally my barrier to entering into Cisco Certification.

Subnetting is something (for the exams especially) you need to drill yourself on constantly as it can quickly slip away. I think the best way to learn the decimal method would be through videos as reading about it is a little hard to follow.

I found Kevin Wallace's videos and Wendell Odom's books the best to teach this method.

rob42

Can you nail down what it is that's confusing for you [subnetting]? For me, I had to be able to understand what was going on at a very 'low level'. That's possibly because of the way that I got into the world for computers. Back-in-the-day, it was 8-bit home computers, Machine Code, and D.I.Y electronics. I learned about the 'zeros' and 'ones' that you needed to put on the wires in order to make things do what you wanted them to do: I've found that the same approach to 'Subnetting' to be a natural progression to make; it's not for everyone.

Some people like what I've done here URL="http://rob42.net/IPv4_Subnets1.htm"]Rob42.net - IPv4 Subnets[/URL, some don't. It's a work in progress, which I'll be expanding upon as and when. It maybe of help to you, and I hope that it is.

I totally get where you're coming from about getting discouraged because other people can learn CCENT in a month. I find the studying VERY tough! I'm not an academic person and find retaining information a HUGH challenge. In fact, I'm not sure that I'll ever get to CCENT, let alone CCNA!. I've been studying for about 5 months, but I don't think I'm even close!

I'm not going to give up, mind. It'll probably take me another year of study and repetition to crack the CCENT exam, but I'm going to do it!

*-Never Give Up-*

wseyller

For practice subnetting I like this site: https://www.subnetting.net/

It does good to gauge how quick you can do the subnetting whether you have to write the binary out or once you finally get it you can do many subnetting problems in your head without a calculator or pencil/paper.

PocketLumberjack

Get the free week trial to itprotv and watch the Todd Lammle subnet videos. His way is so simple I can do Class As in my head quickly.

Uriah7

I second PocketLumberjack. Todd Lammle teaches it the best way. I studied for a few months and passed the CCENT without feeling like I was ready for it. Use Todd's books and videos from ITProTV and you will be fine. Absorb yourself into the material and don't let anything distract you. You can do it.

volfkhat

Raymond Mason wrote: »

I believe I used the binary method, I can try it but I doubt its going to be much easier.

Yaw,
the binary method is simply to show you that there is indeed a "method to the madness".

But once you accept that it's legit math..... you don't really need to use it (by pencil/paper).

Instead, i learned the MAGIC# method;
AFter about a week... i Had subnetting down cold (could do it All in my head).

https://www.youtube.com/playlist?list=PL33E07ECCA73C0755
Start with video 46 :]

It just takes practice/repetition (and a little **** sheet)

Raymond Mason

Well, I pin pointed the problem and I think it boils down to my basic arithmetic skills.

In the magic number method, let's say I had the IP address 172.21.45.143 with a mask of /22

Subnet question: You are given IP address 172.21.45.145/22. What is the first valid host on address on this subnet?

In binary it is 11111111.11111111.11111100.00000000

The magic number is 4 and I know I have to count by 4's in my head. I will time myself to see how fast I can count by 4's to get to 45 eventually.

44. 1 minute and 8 seconds

I stopped just before I hit 45.

Let me try to count by 8's 5 times in my head. I will time it as well.

40 - 30 seconds so I guess that is not nearly as bad as counting by 4's

Going to try to count by 16's 8 times.

48 - 54 seconds and I lost count so I couldn't go any higher without starting over.

dontstop

A quick tip. Every mask has a 128 Network ID. That means that every Magic number is a multiple of 128. That cuts your time in half for finding the network ID. Also you can count backwards from 256.

Another tip would just be to quickly try and find multiples. We know that 4 is the Subnet Address so 0 4 8 etc. are all Subnet IDs

e.g. 45 (with a magic number of 4)
4 * 10 = 40 (too low) (step 1)
40 + 4 = 44 (too low) (step 2)
44 + 4 = 48 (too high) (step 3) (^ go back)

Work on getting quicker after a while the numbers occur over and over again so you start to know round about were the address is.

Also even a minute is quick compared to doing the binary method. It sometimes takes me 60+ seconds to just write out some of the number in binary and convert them.

volfkhat

It sounds like you are closer than you think :]

But allow me to give you 2 "cheats" that will get you to the Finish line.

**** #1

Raymond Mason wrote: »

The magic number is 4 and I know I have to count by 4's in my head. I will time myself to see how fast I can count by 4's to get to 45 eventually.

Now there's your problem;
Use pencil & paper!
Seriously.
Cisco gives you something to write on during the test.
So give yourself a break :]

1 minute 8 seconds is pretty darn slooow.
lol

i would bet a $10 banknote that you can count faster by using your own FINGERS :]
Seriously!

COUNT with your LEFT hand, and WRITE with your RIGHT hand:

1-2-3-4
*writes down #4
5-6-7-8
*writes down #8
9-10-11-12
*writes down #12
13-14-15-16
*writes down #16
17-18-19-20
*writes down #20
21-22-23-24
*writes down #24
25-26-27-28
*writes down #28
29-30-31-32
*writes down #32
33-34-35-36
*writes down #36
37-38-39-40
*writes down #40
41-42-43-44
*writes down #44
45-DING DING DING.
You made it :]

Grab your stopwatch and Give it a shot yourself.
Let me know if it's faster/slower/easier/ or harder.

If you get comfortable, then we can move on to **** #2 :]

yoba222

When I took the CCENT, the first thing I did was write out 0 4 8 12 16 ... all the way to 256 down the side of the dry erase board. Then I circled every other 4 so I had a way to quickly see where the blocks of 8 land.

Prevents stupid math mistakes. This way at a quick glance you can tell if 192.168.1.200/29 lands right on the subnet number or if it is one of the 6 assignable IP addresses, for example.

I finished the CCENT extremely quickly.

Raymond Mason

Thank you everyone for the help! I have solved some subnet questions now. Great tips!

I just got to now keep practicing while I study the other parts of the CCENT.

volfkhat

Raymond Mason wrote: »

Thank you everyone for the help! I have solved some subnet questions now. Great tips!

I just got to now keep practicing while I study the other parts of the CCENT.

DUDE... we didn't finish our lesson. You forgot about **** #2.

Consider this:
What If i had a network,
and it had a subnet-mask with --> "192" in it.

What can you tell me about the network?

chopsticks

OP, all the way!

rob42

volfkhat wrote: »

DUDE... we didn't finish our lesson. You forgot about **** #2.

Consider this:
What If i had a network,
and it had a subnet-mask with --> "192" in it.

What can you tell me about the network?

As I'm following this thread, I would really like you to continue.

If I may...

If you have a '192' as part of the Mask, the Broadcast Address will contain a '63', because 192 = 1 1 0 0 0 0 0 0 and 63 = 0 0 1 1 1 1 1 1. [192+63=255]

So, if the Mask is 255.192.0.0, the Broadcast for that Network will be x.63.255.255

If the Mask is 255.255.192.0, the Broadcast will be x.x.63.255.

For 255.255.255.192 -- x.x.x.63

Is that what you're driving at?

volfkhat

rob42 wrote: »

If the Mask is 255.255.192.0, the Broadcast will be x.x.63.255.

For 255.255.255.192 -- x.x.x.63

Is that what you're driving at?

Yes, partly.

i'm really trying to show that you have to think broader.

if the subnet mask was 255.255.255.192.... then yes, the blocksize is 64.

But if the subnet mask was 255.255.192.0... the blocksize is also 64.

And if the subnet mask was 255.192.0.0... the blocksize is 64 (yet again).

There is a fairly obvious pattern at work here.
ANd once you "see" it... there really isn't much "math" to do when you subnet.

Let's try another one:
Assume that your subnet-mask contains a "224"...

What are the possible subnet-masks... and what is the blocksize of each subnet?
:]

rob42

Well, again, I'd work it like this...

255-224=31

B/Casts:
x.31.255.255
x.x.31.255
x.x.x.31

Masks:
255.224.0.0
255.255.224.0
255.255.255.224

Block Size = 32 (0 -- 31)

So the Subnets will be multiples of 32...

0
32
64
96
128
160
192
224

volfkhat

Yeppers.

Mask - Blocksize
.0 = 256
.128 = 128
.192 = 64
.224 = 32
.240 = 16
.248 = 8
.252 = 4
.254 = 2

and regardless of the octect... the pattern stays the same :]

rob42

Cool!! So, knowing how the Block Size relates to the Mask, reduces the mental gymnastics you need to do.

Thank you. It wasn't until you pointed it out, that I twigged onto the relationship. -- Top man!

volfkhat

rob42 wrote: »

Cool!! So, knowing how the Block Size relates to the Mask, reduces the mental gymnastics you need to do.

Thank you. It wasn't until you pointed it out, that I twigged onto the relationship. -- Top man!

You got it!
and now you understand the Magic# method.
The "Block size" is the "Magic#".

(in fact, if you look closely... each line adds up to 256)

CiscoNet Solutions

subnetting is based on the following:

- what is the network portion and host portion
- converting between binary and decimal
- determine network boundary and subnet multiples

https://www.slideshare.net/shaun_hummel/ip-addressing-and-subnetting-quick-reference-for-ccna