Simple Subnetting
Simple and Quick way to Subnet
On this page you will learn how to subnet in a simple and quick way if you are on the go or are just bored of the way other people teach you. Some materials you might need:
- calculator
- pen
- paper
Step 1
Write out the subnetting cheat chart on a piece of paper. You need to be able to do it by hand in case you have to work out subnetting problems in your head or in an exam.
Step 2
Look at the IP address and subnet mask. If the subnet mask is written out in abbreviated form (called CIDR) then just count up in blocks of eight and add the last few numbers to reach the subnet mask. e.g.
192.168.1.23/26 - you will to work out what the slash 26 actually is when written out as a full subnet. The binary math section tells you that 255 in binary is equal to 8 and we need to reach 26 so..
255 is 8 255.255 is 16 bits 255.255.255 is 24 bits and to get to 26 we need to add 2 to 24 so tick two places down on the top left column on the subnetting cheat chart.
128< 192< 224 240 248 252 254 255
So you can see that by counting down two (which is 24 + 2 = 26 bits) you have generated the subnet mask of 255.255.255.192 which if you write out in binary bits is 26 binary bits (or 8 + 8 + 8 + 2).
if you don't understand that then try it this way: you are pretty much starting at 1 and literally working your self all the way to the left, up, then all the way to the right. You are counting up by powers of 2. When you get to the top (128) you will say:
128 + [64] = 192, 192 + [32] = 224, 224 + [16] = 240, 240 + [8] = 248, 248 + [4] = 252 and etc
Step 3
Take the same number across the top row of the Subnets.
128 64 32 16 8 4 2 1
The above table is one binary octet written out in decimal. Whichever number your last tick ends at tells you which number your subnets begin on.
So you have it numbered 64 which means that our subnets are going up in increments of 64. Your host number out of the IP address 192.168.1.23 is the number 23. It is 23 because 192 is a traditional class C address so we can only use numbers in the last octet for IP addresses.
write out your subnets counting up in increments of 64. You are allowed to start with IP subnet zero because the guys who invented the RFC (requests for comment) for subnetting designed it to permit that.
192.168.1.0 - this is the first subnet and is known as the zero subnet. Host number 23 is in here because if you go any further you will have gone past 23.
192.168.1.64 - we have added the first 64 to the end.
192.168.1.128 - we have added another 64 to the end. This is your 3rd subnet.
192.168.1.192 - our last subnet. Can't go higher because the SM ends in 192.
to answer the question 'which subnet is host 192.168.1.23 in is subnet 192.168.1.0
Complete!
Here is a quick and simple way to learn subnetting if are you in a hurry.