A Q for those past Cisco Net Acad Class 1

I'm wondering if the curriculum goes more in-depth with subnetting than the 5 pages I just read that hasn't even defined what a block size is, has already touched on VLSM, and other subnet-related topics or if I should start reading up on subnetting on my own.

I've been studying the same five pages for the past five hours, but there simply is NOT enough information for me to grasp the concept. I understand the concept of borrowing the bits and how each bit essentially gives to subnets, and how to determine the network and broadcast address, but it really doesn't mention much else regarding subnetting.

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ziggi138

When i went through the academy; we went in depth with subnetting. I guess it depends on your teacher.

sentimetal

The class is in 12 hours - I just read the few pages the book has on it and decided to look at some subnetting questions and realized there's not much the book itself teaches on it (especially in regards to the questions asked on websites like subnettingquestions.com.)

I'll see what we go over tonight / the instructor has planned, and then determine whether or not to buy the Sybex book; I'm already using CBT Nuggets.

tomaifauchai

Aren't you using the web-based flash CCNA curicullum from Netacad or (CCNA Exploration 4.0) ? It is well explained!
We passed at least 8-9 hours on this subject in class

sentimetal

tomaifauchai wrote: »

Aren't you using the web-based flash CCNA curicullum from Netacad or (CCNA Exploration 4.0) ? It is well explained!
We passed at least 8-9 hours on this subject in class

I am. I have the basics down, but the diagrams kind of just say what they're doing and not explaining why they're doing them; I've figured quite a bit on my own - hopefully the teacher will assist.

spiderjericho

There are subnetting problems in the Network Fundamentals and Routing Protocols and Concepts workbook.

Also, the chapter discusses ANDing, decimal to binary conversion and how to subnet/VLSM.

Depending on your instructor, you can go very in detail.

sentimetal

Welp, we went over the chapter in Fundamentals and he stressed that we should AND everything. I'll give it a shot, but from what I've been learning from other sources, there are much better ways subnet than AND out every octet.

spiderjericho

There are many ways to skin a cat. I, personally, from my years of teaching exploration can do subnetting in my head. But in the short term, try out the subnetting by requirement (how many hosts or how many networks). Or if you can get your hands on a copy of Todd Lammle's book, he has numerous problems. Also, you can ask your instructor for a copy of the subnetting workbook in the netacad tools. Subnetting is one of the key topics on the CCNA exam.

sentimetal

spiderjericho wrote: »

There are many ways to skin a cat. I, personally, from my years of teaching exploration can do subnetting in my head. But in the short term, try out the subnetting by requirement (how many hosts or how many networks). Or if you can get your hands on a copy of Todd Lammle's book, he has numerous problems. Also, you can ask your instructor for a copy of the subnetting workbook in the netacad tools. Subnetting is one of the key topics on the CCNA exam.

I can subnet a C class just fine in my head - I still don't quite grasp what I'm missing when I come across a class A or B subnet with a, /8 or /14 or any other A-B prefix. I can tell you the subnet mask of such addresses, but that's about it. I.E. I have no idea what to do with a 10.0.0.0/14 subnet; I get lost after the fact that you're borrowing the 6 bits for additional networks.

I have CBT Nuggets CCNA videos, and will try to get my hands on Lammle's book. I do also have the CCNA Exploration work book, also.

tomaifauchai

sentimetal wrote: »

I have no idea what to do with a 10.0.0.0/14 subnet; I get lost after the fact that you're borrowing the 6 bits for additional networks.

If it can help you to understand, a /14 is the same as a /22, exept it's not on the same octet! (Mask wise)
A /16 is the same as a /24, exept it isnt on the same octet! (Mask wise)

Of course, the number of hosts and subnets available changes, but basically you're splicing the whole thing the same way.

For your question,
10.0.0.0/14 is a /16 with 2 more bits borrowed for the subnets. (2^2 = 4)

(What i am saying in my head is basically, /14 is four /16 because of the 2 bits borrowed)

Hosts are

10.0.0.1 to 10.3.255.254
10.1.0.0 is a valid IP address
10.2.0.0 is a valid IP address
10.3.0.0 is a valid IP address
10.0.0.0 is the network
10.3.255.255 is the broadcast

Another example could be something more easier...
192.168.0.0/23
1 bit borrowed from a /24 (2^1) = two /24

192.168.0.1 - 192.168.1.254
192.168.1.0 is a valid IP
192.168.0.0 is the network
192.168.1.255 is the bcast

Hope this helps, each guy has his own method and after some times, you'll find the right one for you!
There's a very good sheet in the Curriculum somewhere, let me find it

sentimetal

tomaifauchai wrote: »

If it can help you to understand, a /14 is the same as a /22, exept it's not on the same octet! (Mask wise)
A /16 is the same as a /24, exept it isnt on the same octet! (Mask wise)

Of course, the number of hosts and subnets available changes, but basically you're splicing the whole thing the same way.

For your question,
10.0.0.0/14 is a /16 with 2 more bits borrowed for the subnets. (2^2 = 4)
(What i am saying in my head is basically, /14 is four /16 because of the 2 bits borrowed)

Hosts are
10.0.0.1 to 10.3.255.254

10.1.0.0 is a valid IP address

10.2.0.0 is a valid IP address

10.3.0.0 is a valid IP address

10.0.0.0 is the network

10.3.255.255 is the broadcast

Hope this helps, each guy has his own method and after some times, you'll find the right one for you!

So you turned 10.0.0.0/14 into 10.0.0.0/16, which gives you four subnets and a mask of 255.255.0.0, but for a a Class A and B subnet, how do I figure out the number hosts and the host range? It's easy for a C (2^n - 2 = number of hosts per subnet).

Also, do the sequence of the addresses go in such an order:
10.0.0.255
next ip: 10.0.1.0
or
10.0.1.255
next ip: 10.0.2.0

tomaifauchai

sentimetal wrote: »

So you turned 10.0.0.0/14 into 10.0.0.0/16, which gives you four subnets and a mask of 255.255.0.0

It's not exactly the case.

[LIST]
[*]10.0.0.0/16 = [B]10[/B].[B]0[/B].[COLOR=Red]0.1 - [COLOR=Black][B]10.0[/B][/COLOR].255.254[/COLOR] = (2^16) - 2
[*]10.0.0.0/14 = [B]10.0[/B].[COLOR=Red]0.0[/COLOR] - [B]10.3[/B].[COLOR=Red]255.254[/COLOR] = (2^1[IMG]https://us.v-cdn.net/6030959/uploads/images/smilies/icon_cool.gif[/IMG] - 2
[/LIST]

So basically, when you look at this, you say..well my /14 contain FOUR /16 because you borrowed 2 bits from the /16, but it's just a way to understand things. You can sub-subnet the /14 into what you want, really.

But it's something you'll learn later. For now, it's just important you get how to borrow bits from subnet portion and from hosts portion. I always prefer borrowing the subnet portion. But you might prefer the opposite, like i said, it's up to you.

For now, you should focus borrowing bits from the hosts portion /25,/26..and so on.

Open your NetAcad curricullum and go to section 6.5.3.5 and print that VLSM Subnetting chart PDF on your left, it is very useful !

sentimetal wrote: »

Also, do the sequence of the addresses go in such an order:
10.0.0.255
next ip: 10.0.1.0
or
10.0.1.255
next ip: 10.0.2.0

Both are good, if we stay in the /14

sentimetal

tomaifauchai wrote: »
It's not exactly the case.
[LIST]
[*]10.0.0.0/16 = [B]10[/B].[B]0[/B].[COLOR=Red]0.1 - [COLOR=Black][B]10.0[/B][/COLOR].255.254[/COLOR] = (2^16) - 2
[*]10.0.0.0/14 = [B]10.0[/B].[COLOR=Red]0.0[/COLOR] - [B]10.3[/B].[COLOR=Red]255.254[/COLOR] = (2^1[IMG]https://us.v-cdn.net/6030959/uploads/images/smilies/icon_cool.gif[/IMG] - 2
[/LIST]
So basically, when you look at this, you say..well my /14 contain FOUR /16 because you borrowed 2 bits from the /16, but it's just a way to understand things. You can sub-subnet the /14 into what you want, really.

But it's something you'll learn later. For now, it's just important you get how to borrow bits from subnet portion and from hosts portion. I always prefer borrowing the subnet portion. But you might prefer the opposite, like i said, it's up to you.

For now, you should focus borrowing bits from the hosts portion /25,/26..and so on.

Open your NetAcad curricullum and go to section 6.5.3.5 and print that VLSM Subnetting chart PDF on your left, it is very useful !

Both are good, if we stay in the /14

I have that PDF saved, but have not looked at it.

So
10.0.0.0/16 = 10.0.0.1 - 10.0.255.254 = (2^16) - 2

This is a network with 65,536 addresses - 2 for the broadcast and network itself. That gives us 65,534.

How would I figure out the maximum host address without counting up manually? I was shown the ANDing technique, but he never explained /how/ that 3rd octet became 255 - he just said to pretend that the subnet mask and IP address had all 1s there...

(thanks for helping btw)

/edit: Also, now I realized when I said /16 I was subnetting a subnet, I was kind of mixed up there. Woops.

tomaifauchai

sentimetal wrote: »

I have that PDF saved, but have not looked at it.

So
10.0.0.0/16 = 10.0.0.1 - 10.0.255.254 = (2^16) - 2

This is a network with 65,536 addresses - 2 for the broadcast and network itself. That gives us 65,534.

How would I figure out the maximum host address without counting up manually?

(thanks for helping btw)

It's always (2^n) - 2

But with the time, you'll just memorize the common ones.
....
/22 = 1024 - 2
/23 = 512 - 2
/24 = 256 - 2
/25 = 128 - 2
/26 = 64 - 2
.....
Got the pattern?

sentimetal wrote: »

he just said to pretend that the subnet mask and IP address had all 1s there...

(thanks for helping btw)

/edit: Also, now I realized when I said /16 I was subnetting a subnet, I was kind of mixed up there. Woops.

The addresses included in a subnet, can be 0 or 255 in some cases, if your subnet mask is less than /24.
I forgot to mention it early, but from your 10.0.0.0/14, the
10.0.255.255
10.1.255.255
10.2.255.255
are also valid IP's

Check your Private messages!

sentimetal

tomaifauchai wrote: »

It's always (2^n) - 2

But with the time, you'll just memorize the common ones.
....
/22 = 1024 - 2
/23 = 512 - 2
/24 = 256 - 2
/25 = 128 - 2
/26 = 64 - 2
.....
Got the pattern?

Yep, I got the pattern. What I meant, though is with

10.0.0.0/16 - you have 65,534 host addresses. What method did you use to figure out that the maximum host address is 10.0.255.254?

tomaifauchai

sentimetal wrote: »

Yep, I got the pattern. What I meant, though is with

10.0.0.0/16 - you have 65,534 host addresses. What method did you use to figure out that the maximum host address is 10.0.255.254?

10.0.0.0/16
255.255.0.0
11111111.11111111.00000000.00000000

1st octet = always 10
2nd octet = always 0
3rd octet = 0-255
4th octet = 0-254

10.0.0.0/14
255.252.0.0
11111111.11111100.00000000.00000000

1st octet = always 10
2nd octet = 0-3
3rd octet = 0-255
4th octet = 0-255 for 10.0.0.0, 10.1.0.0, 10.2.0.0 and 0-254 for 10.3.0.0

sentimetal

tomaifauchai wrote: »

10.0.0.0/16
255.255.0.0
11111111.11111111.00000000.00000000

1st octet = always 10
2nd octet = always 0
3rd octet = 0-255
4th octet = 0-254

What if you were to subnet that network with 8 subnets?

10.0.0.0/19
255.255.224.0
2^13 - 2 = 8190

So we have 8190 hosts! How would you figure out the maximum host?

tomaifauchai

sentimetal wrote: »

he just said to pretend that the subnet mask and IP address had all 1s there...

(thanks for helping btw)

/edit: Also, now I realized when I said /16 I was subnetting a subnet, I was kind of mixed up there. Woops.

sentimetal wrote: »

What if you were to subnet that network with 8 subnets?

10.0.0.0/19
255.255.224.0
2^13 - 2 = 8190

So we have 8190 hosts! How would you figure out the maximum host?

11111111.11111111.11100000.00000000

1st method

You borrow 5 bits from the 3rd octet
So that would mean 2^5 = 32
10.0.0.1 - 10.0.31.254
1st octet = always 10
2nd octet = always 0
3rd octet = 0-31
4th octet = 0-255, 254 for the last

2nd method (Lazy method) This is the one i prefer and is very fast for the exam.

You take the mask 255.255.224.0
You do the substraction of 256 - 224 = 32
32 is the step/range you would get from the starting point of your network.
10.0.0.1 - 10.0.31.254

If your network is 10.0.32.0/19, you do the same..and you get your way through 10.63.255.254 as your last useable host.

CodeBlox

I did the netacad program through my community college. The idea of a multiplier is how I learned it easily.
Example

Take class A. You need 62 subnets

that would be a /14 || 255.252.0.0

The multiplier = place value of least significant subnet bit which is 4 in this case

So your multiplier (which is 4 in this case) determines the subnets and you increment that "special octet" by the multiplier.

subnets would be:
10.0.0.0
10.4.0.0
10.8.0.0
...
10.248.0.0
10.252.0.0 <-- broadcast subnet

Thats the way I learned it. The netacad curriculum does do a good job explaining subnetting though.

sentimetal

CodeBlox wrote: »

I did the netacad program through my community college. The idea of a multiplier is how I learned it easily.
Example

Take class A. You need 62 subnets

that would be a /14 || 255.252.0.0

The multiplier = place value of least significant subnet bit which is 4 in this case

So your multiplier (which is 4 in this case) determines the subnets and you increment that "special octet" by the multiplier.

subnets would be:
10.0.0.0
10.4.0.0
10.8.0.0
...
10.248.0.0
10.252.0.0 <-- broadcast subnet

Thats the way I learned it. The netacad curriculum does do a good job explaining subnetting though.

I'm actually starting to get it.

Your ranges would be
10.0.0.1 - 10.3.255.254
10.4.0.1 - 10.7.255.254 etc, right?

I'm going to have to reread chapter 6 to see why I am claiming it didn't explain it well. Honestly, though, this thread, a few friends, and the internet have been a huge help.

CodeBlox

Yeah, and its still best to know the binary math behind it. That way if you aren't sure you can resort to it. If your subnet bits change, it's a different subnet.

/14 is 6 subnet bits

10.4.0.0 /14 = 10.0000 0100.0.0
10.8.0.0 /14 = 10.0000 1000.0.0

see how the blue subnet bits change? Means its a different subnet. Thats a way to check if you're correct. May take longer but it helps while learning. I don't need to do it this way anymore though and can do it in my head.

Since the red bits are host bits, they can be any variation within a subnet. So long as you don't change the blue ones, you're still in the same subnet.

tomaifauchai

CodeBlox wrote: »

The idea of a multiplier is how I learned it easily.

Me too and it's very fast to reverse engineer IP/Subnet/Mask questions.
You only have to learn the masks on your fingertips. I've posted a good topic about it somewhere..check this out. Some of the tips i use, like knowing the middle etc...

http://www.techexams.net/forums/ccna-ccent/61837-can-anyone-explain-subnet-255-255-254-0-a.html#post487578

sentimetal

CodeBlox wrote: »

Yeah, and its still best to know the binary math behind it. That way if you aren't sure you can resort to it. If your subnet bits change, it's a different subnet.

/14 is 6 subnet bits

10.4.0.0 /14 = 10.0000 0100.0.0
10.8.0.0 /14 = 10.0000 1000.0.0

see how the blue subnet bits change? Means its a different subnet. Thats a way to check if you're correct. May take longer but it helps while learning. I don't need to do it this way anymore though and can do it in my head.

Since the red bits are host bits, they can be any variation within a subnet. So long as you don't change the blue ones, you're still in the same subnet.

I do. 10.0010000.0.0 - 16 would be the next one.
10.0010100.0.0 - 20 the next
10.0011000.0.0 - 24 the next
10.0011100.0.0 - 28 the next
10.0010000.0.0 - 32 and so on

I understand binary, but I do have a much easier time doing it in my head than writing it out IN binary.

For someone who started Sunday night at 8pm, I feel like I've made progress.

CodeBlox

sentimetal wrote: »

I do. 10.0010000.0.0 - 16 would be the next one.
10.0010100.0.0 - 20 the next
10.0011000.0.0 - 24 the next
10.0011100.0.0 - 28 the next
10.0010000.0.0 - 32 and so on

I understand binary, but I do have a much easier time doing it in my head than writing it out IN binary.

For someone who started Sunday night at 8pm, I feel like I've made progress.

Actually the next one would be :
10.0000 1100.0.0 /14

Which is 10.12.0.0, after that would be 10.16.0.0

Other than that you're right. Just practice a bunch.

sentimetal

CodeBlox wrote: »

Actually the next one would be :
10.0000 1100.0.0 /14

Which is 10.12.0.0, after that would be 10.16.0.0

Other than that you're right. Just practice a bunch.

Gah, that was carelessness on my part; maybe that's why I always received B or B+ grades in math classes - carelessness.

I really get this stuff now, and it is definitely thinks to you all. I have to admit that my mind goes a bit blank when I sit at subnettingquestions.com, but I'm sure with practice I'll get it down. x]