Subnet Class C Network

Subnetting is the process of breaking down one network, into many smaller networks.  There are a few reasons you why you would want to implement subnetting on your network.  One of the reasons you would want to subnet a network is to lower the network traffic load, resulting in increased network performance.  Another good reason to subnet a network is because this allows you to administrate your network more easily.

Think about it, what if there was a problem with your network and you had to repair the problem?  With subnetting in already in place, you will be able to section off what part of the network is having the problem and repair the network quicker.  In this article I will be showing you just the basics of subnetting a network, but I will be writing more advanced subnetting articles in the future.

Before you begin subnetting a network you will need to ask yourself a few questions.  First of all you need to ask yourself; how many networks do I need?  Also you need to ask yourself how many hosts I need to be able to accommodate.  If you want to find out what your current subnet mask is, open up command prompt on a Windows based pc and type in ipconfig.

In order for you understand on how subnet a network, you first need to know how to convert decimal into binary. As you can see from the chart below that there are three different classes that you can use to subnet your network.  There are actually a few more subnet classes out there, but they are being used for research.

Subnet Classes

Class Subnet Format CIDR
A 255.0.0.0 Network.Host.Host.Host /8
B 255.255.0.0 Network.Network.Host.Host /16
C 255.255.255.0 Network.Network.Network.Host /24

In a class c subnet all you need to worry about is the last octet, which is the zeros.  So in a class C scheme the subnet decimal form of 255.255.255.0 is equal to 11111111.11111111.11111111.00000000 in binary form.  When you look at the chart below, look at the binary column and in the binary column the 1′s represent networks, while the 0′s represent hosts.

Class C Subnet Masks

Binary Decimal CIDR Subnet Mask
00000000 0 /24 255.255.255.0
10000000 128 /25 255.255.255.128
11000000 192 /26 255.255.255.192
11100000 224 /27 255.255.255.224
11110000 240 /28 255.255.255.240
11111000 248 /29 255.255.255.248
11111100 252 /30 255.255.255.252

So if you were given the ip address of 192.168.1.0 with the subnet mask of 255.255.255.192. How many subnets do you have and how many hosts in each subnet?  Well if you look at the chart above you see the subnet mask for 255.255.255.192 and there are two binary 1′s and six binary 0′s.  To figure out the amount of subnets you have you can use this easy formula.

Subnets = 2Network Bits

So if you take the above example, since you have 2 bits for the network. All you have to do is use the equation Subnets = 22 which is 4 subnets. Now if you wanted to figure out home many hosts you can have on each of the four subnets you would use the equation below.

Host = 2Hosts Bits - 2

So since you have 6 bits located in the subnet mask dedicated for hosts, once again just use the equation above. Hosts = 26 – 2 which is 62 available host ip addresses.  The reason that you have to minus two is because one ip is reserved for the network address and the other is reserved for broadcast addresses. So in all reality there really are 64 host ip addresses, but there are only 62 available ip addresses that you can use in each subnet to assign to your different network devices.

So now let’s figure out valid ip ranges for each subnet, also the network and broadcast addresses for each subnet.  So all you have to do to figure out the ip range for each subnet is to first figure out what the subnets are the first place.  Well since our ip address is 192.168.1.0 that will be our first subnet.  The next subnet can be found by adding 64 to the end of 192.168.1.0 which is 192.168.1.64.  You can then find the third subnet by again adding 64, but this time add it to 192.168.1.64 which is 192.168.1.128.  And finally again repeat the process 192.168.1.128 + 64 = 192.168.1.192.  You would stop here because if you added another 64 to 192.168.1.192 you would get 192.168.1.256, which is not valid and would be located in a totally different network.

So now you need to figure out the valid ip ranges for each subnet.  We will again start back at with the ip address 192.168.1.0  Since we know that the network address 192.168.1.0 is currently in use and cannot be assigned, the next available address is 192.168.1.1.  So 192.168.1.1 will be our first assignable ip address.  To figure out the broadcast address, simply go to the second network address and minus 1.  So if you took 1 away from 192.168.1.64 you would get 192.168.1.63 for a broadcast address.  So you now know that the ip address 192.168.1.0 is the network address and the broadcast address is 192.168.1.63, you network range would be 192.168.1.1 to 192.168.1.62.

Network Address Ip Range Broadcast Address
192.168.1.0 192.168.1.1 to 192.168.1.62 192.168.1.63
192.168.1.64 192.168.1.65 to 192.168.126 192.168.1.127
192.168.1.128 192.168.1.129 to 192.168.1.190 192.168.1.191
192.168.1.192 192.168.1.193 to 192.168.1.254 192.168.1.255