IP Subnetting - Network Based

This is truly one of the topics that i would love to teach, as I managed to learn it & love it while researching on it. I honeslty hope that I am able to explain this in a way that anyone & everyone who reads it the first time understands it & if not master it, atleast has the basics to perform the subnetting.

Before we proceed with the subnetting we need to know what are the requirements for the network. Hence looking at the network digram below, you need to determine the number of networks required. Once you have them they can furhter be subnetted using VLSM or CIDR methods, which i will not cover here.



Class C Address : 216.21.5.0
Subnetmassk     : 255.255.255.0
N.o Networks     : 5

So now that we know that our requirement is for 5 networks, we can not begin with our calculation for subnetting.

Bits Chart : 4096 - 2048 - 1024 - 512 - 256 - 128 - 64 - 32 - 16 - 8 - 4 -2 - 1

 

Looking at the requirement we know that 5 networks that we are looking for are somewhere between bit scale 8 - 4. Now we need to select the closest bit that can fullfil our requirement which here in this case is bit scale 8 that can be used to calcuate the number of network bits for our network.

 

5 Networks : 3 bits (8-2 = 6) : /24 + 3 = 27 N/bits

Hence the new subnet mask - 255.255.255.224

The Increment is 32 as the total network bits are 27. This can be further explained using the binary method.

 

Firstly, all you need to do is to convert each oct of the subnet mask to binary. Then using the bit scale you can determine the increment value to pull out a network from the pool given.

 

So below is how a standard class C-Subnet mask look like when in binary.

          

 

 

  

 

 

When we add the the the network bits to the subnet, it looks something like

 

 

 

 

        Do remember, whenever we talk about the network, we add the borrowed bit from the left side. As you can now see after adding the 3 bits we now have a new subnetmask of 224 or /27. As the last active bit is 32 in the 4th oct, it will also be used as the increment to get our five networks.

 

Therefore using 32 as the increment for the POOL 216.21.5.0 we get the following networks

 

216.21.5.0     ---- 216.21.5.31 

216.21.5.32   ---- 216.21.5.63

216.21.5.64   ---- 216.21.5.95

216.21.5.96   ---- 216.21.5. 127

216.21.5.128 ---- 216.21.5.159

 

I know many of you will be pointing out that the /27 is not at all a good practice to use between the routers & / 30 should have been used. The point here is to teach the basics of subnetting & designing an actual network type. Therefore for many of you my method may not be wise & I truly respect it.

If you however have a better method, or can help explain subnetting better, please do send in the post. Also if you find any site explaining it in a better way or manner, do not heistate to send in the link of the site.

Again I hope you like this & would apprecaite any comments or suggestion.