Grandpa’s will and IP subnetting

IP addressing and subnetting. Any number of times you read and try to apply, the basics evaporate in no time. Subnetting is little tricky and hence needs working through it to stick in the head. Let me make an attempt to give you some help in grasping the concept.

Get this one right. Subnetting is all about dividing a large network to a fairly manageable smaller groups or sub networks. Even before we go and divide the networks into smaller groups, it is divided already into class A,B and C networks. Let’s understand this division first.

Imagine this. Grandpa in his last days left a will to three of his sons Ason, Bson and Cson. Ason is eldest and Cson, the youngest.

To keep everyone happy and avoid any possible conflict Grandpa has done some homework and marked all the land he has to pass on. This is a clever division keeping in mind that eldest should get the lion share but again younger ones should not be disappointed. Hence the shape of the property.

Ason gets the taller box. It can accommodate only few but very very lengthy streets. So he can build many number of houses in a row. Bson’s box is little regular shaped. It can accomodate average number of streets and average number of houses per street. Cson has got a narrow wider strip of land, so he can have very few number of houses but large number of streets.

Class A network can have – 128 networks [streets] and 16 lakh machines [houses] per street. Class B can have – 16000 networks [streets] and 1/2 lakh machines [houses] per network. Class C can have – 2 lakh streets and just 250 machines [houses] per network.

Once this land is handed over to these three sons, they can rework within the allotted area . It’s upto the individual to come up with the desired number of streets and so many houses per street. So this is where subnetting will begin.

If Cson decides to increase the number of streets he might end up with an absurd situation like having one house per street. Similarly, if Ason decides to keep very few number of streets, he might have to line up the houses for miles together in a row that it may not be called a street.

So, a balance needs to be found in keeping the street length reasonably lengthy and with good number of houses. This is what subnetting is all about.

PS: Well, it took me nearly 6-8 hours of constant thinking to pick the topic, state the problem, referring the text, spin a story and illustrating with the free hand cartoon. Believe me, it’s not as easy it looks here.