Comments on: Cool Subnetting Tricks with Variable Length Subnet Mask

By: jayaraju

jayaraju — Fri, 22 Jan 2010 10:15:15 +0000

ultimate…………….

By: FernanDOG

FernanDOG — Sat, 10 Oct 2009 03:18:49 +0000

Hi
This is a very useful artical. Simple and Sweet. Diagrams and tables are simple to
understand
thumbs up from me
Thanks a lot
fer

By: chinedu God'swill

chinedu God'swill — Wed, 30 Sep 2009 17:02:57 +0000

Sir,please explain the difference between RIP and OSPF

By: wushu

wushu — Mon, 02 Feb 2009 08:01:50 +0000

i have problem in indicating numbers, what number should i use why should i use it, how did you get?

huhuhuhu… please help

By: Wushu

Wushu — Mon, 02 Feb 2009 07:44:36 +0000

i still don’t get it… T_T

i need a further explanation… pls help…

By: franklin

franklin — Thu, 25 Sep 2008 12:19:56 +0000

Good job, I think their is a mistake wirh the network E and F. The reason been that
192.168.10.44/26 and 192.168.10.108/27 is not a subnet address.

I stand to be corrected, I think since network E needs 40 hosts, The easiest way to assign the subnet is to assign the largest first. Hence.

Network E 192.168.10.0/26
Network F 192.168.10.64/27
Network A 192.168.10.96/27
Network B 192.168.10.104/30
Network C 192.168.10.108/30
Network D 192.168.10.112/30

Thank you

By: Mark Angelo S. illustrisimo

Mark Angelo S. illustrisimo — Thu, 18 Sep 2008 11:54:46 +0000

110101100.00010000.11111110.00000001
onebyte= eight bits
thirty two bits thnxxxx

By: Adel farid

Adel farid — Sun, 14 Sep 2008 03:36:19 +0000

Thats right actually Stelios good job .

By: Stelios Antoniou

Stelios Antoniou — Wed, 10 Sep 2008 17:21:29 +0000

Very good James,

You are absolutely right. Well, actually the correct sequence should be:

E: 192.168.10.0/26
A: 192.168.10.64/27
F: 192.168.10.96/27
B: 192.168.10.128/30
C: 192.168.10.132/30
D: 192.168.10.136/30

In this way we take advantage of the whole address space.

By: James

James — Wed, 10 Sep 2008 06:29:09 +0000

Maybe I am wrong, but your network E is incorrect. 192.168.10.44/26 is not a subnet address but rather a usable IP address within that block. Maybe this will explain better….

192.168.10.00|101100 (.44 octet in binary, w/ bar separating net and host)

given the above info your subnet would be as follows:

subnet address: 192.168.10.0
broadcast address: 192.168.10.63
first usable address: 192.168.10.1
last usable address: 192.168.10.62

Based on your chart network E has a range of 192.168.10.44 – 107. In order to achieve anything greater than 63, you would have to change a net bit and then would be violating the subnet mask or the /26 part of the network.

Above where I have .44 written in binary there is a bar between the 26th and 27th bit separating the net and host. As I stated the broadcast address (or highest address) is:

192.168.10.63 or 192.168.10.00|111111

Therefore, in order to go any higher (64 – 107), bits to the left of the bar would have to change, but the /26 is saying they cant change.

I hope this makes sense.

By: Paul

Paul — Tue, 02 Sep 2008 16:06:34 +0000

Im almost there probably 90% from fully understanding but still have some confusion great diagrams by the way

where im lost is i can understand which prefix and hence subnet mask to use i.e. a /30 for a WAN link as only 2 hosts needed or a /26 prefix for network E as 40 hosts needed.

I just dont know how the last digit in the 4th octet is known
say for network E the 192.168.10.44/26 where does the 44 comes from?
or for network F the 108 chosen?

By: Msizi

Msizi — Tue, 02 Sep 2008 13:34:59 +0000

Thanks man! I can now say “WHooo” , this really helped me, well written

By: karwan

karwan — Tue, 19 Aug 2008 05:44:03 +0000

Thank you dear
that is realy cool , I hope you be happy in your live .
best regards…………………………………………………….

By: EB Allen

EB Allen — Wed, 02 Jul 2008 21:07:28 +0000

Can you explain the /29 and how it relate to the 248. Is the relationship the same regardless of the number we use?

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By: Rajesh kumar

Rajesh kumar — Sun, 27 Apr 2008 07:14:00 +0000

it’s very nice……understable..

By: Johan

Johan — Mon, 21 Apr 2008 21:17:23 +0000

Hi,

Thanks for this excellent article.

Can you let us know if Subnetting differs when done in a Cisco environment and Microsoft environment ?

Someone once told me, that Cisco networks can use Subnet zero while as Microsoft doesn’t encourage that or something along those lines ?

Can you give some clarity on this please !

Thanks,
Johan

By: dr.zing

dr.zing — Mon, 14 Apr 2008 11:46:12 +0000

Superb Article, and nicely explained with helpful diagrams.