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# Subnetting

5 replies to this topic

### #1 Sharki

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Posted 05 November 2017 - 08:24 PM

Hello everyone, I'm new in this forum, also I'm from Spain, so I'm sorry for all those mistakes because english isn't my native language.

Okay, I'm really confused because my teacher gave us some exercises about Subnetting, but this is making me mad. So, as I don't found information about this, I've needed to resort to this kind of forums.

The question: 10.15.12.3 / 9 -> you need to make 9 subnets, then get the 7th subnet's IP, its mask, and its range.

but I'm confusing as bleep because it makes no sense, at least not for me, if the mask is 9, it means isn't class A, neither B, so...??

9 subnets means 24 = 16 as maximum.

Net   || SNet || Hosts

_______________________

10.0 || 0000 || 000. 0 .0

10.0 || 0001 || 000. 0 .0

10.0 || 0010 || 000. 0 .0

...

10.0 || 1111 || 000. 0 .0

_______________________

how can you get the decimal IP there?

So weird... I'm sorry for my english, and thank you for the help!

Have you all a nice day.

Edited by Sharki, 05 November 2017 - 09:08 PM.

m

### #2 toofarnorth

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Posted 06 November 2017 - 06:36 AM

A /9 network contains 128 class B networks. It is half of a class A network

It is impossible to divide into 9 equal size networks.

You could make 7x /12 networks and 2x /13 networks.

Eg:

Netmask: 255.240.0.0 = 12 11111111.1111 0000.00000000.00000000
Wildcard: 0.15.255.255 00000000.0000 1111.11111111.11111111

Network: 10.0.0.0/12 00001010.0000 0000.00000000.00000000 (Class A)
Broadcast: 10.15.255.255 00001010.0000 1111.11111111.11111111
HostMin: 10.0.0.1 00001010.0000 0000.00000000.00000001
HostMax: 10.15.255.254 00001010.0000 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.16.0.0/12 00001010.0001 0000.00000000.00000000 (Class A)
Broadcast: 10.31.255.255 00001010.0001 1111.11111111.11111111
HostMin: 10.16.0.1 00001010.0001 0000.00000000.00000001
HostMax: 10.31.255.254 00001010.0001 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.32.0.0/12 00001010.0010 0000.00000000.00000000 (Class A)
Broadcast: 10.47.255.255 00001010.0010 1111.11111111.11111111
HostMin: 10.32.0.1 00001010.0010 0000.00000000.00000001
HostMax: 10.47.255.254 00001010.0010 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.48.0.0/12 00001010.0011 0000.00000000.00000000 (Class A)
Broadcast: 10.63.255.255 00001010.0011 1111.11111111.11111111
HostMin: 10.48.0.1 00001010.0011 0000.00000000.00000001
HostMax: 10.63.255.254 00001010.0011 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.64.0.0/12 00001010.0100 0000.00000000.00000000 (Class A)
Broadcast: 10.79.255.255 00001010.0100 1111.11111111.11111111
HostMin: 10.64.0.1 00001010.0100 0000.00000000.00000001
HostMax: 10.79.255.254 00001010.0100 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.80.0.0/12 00001010.0101 0000.00000000.00000000 (Class A)
Broadcast: 10.95.255.255 00001010.0101 1111.11111111.11111111
HostMin: 10.80.0.1 00001010.0101 0000.00000000.00000001
HostMax: 10.95.255.254 00001010.0101 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

Network: 10.96.0.0/12 00001010.0110 0000.00000000.00000000 (Class A)
Broadcast: 10.111.255.255 00001010.0110 1111.11111111.11111111
HostMin: 10.96.0.1 00001010.0110 0000.00000000.00000001
HostMax: 10.111.255.254 00001010.0110 1111.11111111.11111110
Hosts/Net: 1048574 (Private Internet)

The last block in /13 networks:

Netmask: 255.248.0.0 = 13 11111111.11111 000.00000000.00000000
Wildcard: 0.7.255.255 00000000.00000 111.11111111.11111111

Network: 10.112.0.0/13 00001010.01110 000.00000000.00000000 (Class A)
Broadcast: 10.119.255.255 00001010.01110 111.11111111.11111111
HostMin: 10.112.0.1 00001010.01110 000.00000000.00000001
HostMax: 10.119.255.254 00001010.01110 111.11111111.11111110
Hosts/Net: 524286 (Private Internet)

Network: 10.120.0.0/13 00001010.01111 000.00000000.00000000 (Class A)
Broadcast: 10.127.255.255 00001010.01111 111.11111111.11111111
HostMin: 10.120.0.1 00001010.01111 000.00000000.00000001
HostMax: 10.127.255.254 00001010.01111 111.11111111.11111110
Hosts/Net: 524286 (Private Internet)

Hth!

tfn

### #3 Sharki

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Posted 06 November 2017 - 09:48 AM

I'm sorry, but I don't get it >_<

Our teacher is a little fool, so he said we could do it in this way.

00001010. 0000 0000 . 00000000 . 00000000 - Network

00001010. 0001 0000 . 00000000 . 00000000 - First Subnet

...

00001010. 0101 0000 . 00000000  . 00000000 - 7th subnet

Host min:  00001010 . 0101 0000 . 00000000 . 00000001 = 10.48.0.1

Host máx: 00001010 . 0101 1111  . 11111111  . 11111110  = 10.55.255.254

00001010. 1111  0000 . 00000000 . 00000000 - Last subnet

I guess he's wrong, like always in everything... But I can't see why he is.

I mean, I don't understand what you wanted to say about that I can't divide into 9 equal size networks but rather 12 o 13. How I could know that?

also, what mean, 2x or 7x?

I'm sorry for be annoying... >_<

Thank ya!

Edited by Sharki, 06 November 2017 - 09:49 AM.

### #4 toofarnorth

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Posted 06 November 2017 - 11:04 AM

According to my calculations 00001010.01010000.00000000.00000000 should be 10.80.0.0

Using a 0000000.00001111.11111111.11111111 netmask would give a /12 network meaning the last ip would be 10.95.255.254

Perhaps someone else could step in and verify that they get the same result?

tfn

Edited by toofarnorth, 06 November 2017 - 11:04 AM.

### #5 Sharki

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Posted 06 November 2017 - 12:05 PM

Holy crap, you're right, I swear our teacher said that, I just copied it in my notebook, so I don't even take the time to try figure out that was wrong.

Now, that makes sense, just wondering why you could do it in /13 instead of /12.

Anyway, I get it!

Thank you so much!

### #6 Sharki

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Posted 06 November 2017 - 04:36 PM

Okay, here we go once again.

He's wrong, right?....

I mean,

1º Subnet -> 192.168.31.0.     First ip useful -> 192.168.31.1       Last one -> 192.168.31.126      Broadcast -> 192.168.31.127

2º Subnet -> 192.168.31.128  First ip useful -> 192.168.31.129   Last one -> 192.168.31.254      Broadcast -> 192.168.31.255

I'm right, am I not?

Edit: Nevermind, it's hard to explain in english, but he said the first subnet going since 192.168.31.1 untill 192.168.31.129 , I SWEAR THAT.

But, at the same time, the photo makes sense. So, just nevermind xD

I'm sorry haha

Thank yaaaaaaaa >_<

Edited by Sharki, 06 November 2017 - 04:41 PM.

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