Votes: 0Posted On: May 24, 2017 01:56:59
What is a subnet in an IP Address?
The process of dividing the IP block into smaller groups is called subnetting. Suppose any organization is provided with 64 IP addresses. But it has three separate departments of finance, sales and marketing. The organization wants to divide these IP addresses into smaller networks and allocate them to these departments. One method of doing so is to divide the IP addresses into subnets.
When an organization is provided by an IP address block, it generally (not necessarily) uses the first IP as network address. This IP address is used by the network for all communication from the external network. The world recognizes the network address as a point of contact and is unaware of all other IPs in the network. The network IP is basically allotted to the router which routes the data to the internal IPs.
The subnet mask is used to define the block of IP addresses provided to the organization. A block of IP address is represented as "a.b.c.d/n".
The "/n" is called as the CIDR notation.
Calculation of IP range - The "/ " notation after the IP address can be used to calculate the IP address range that falls under that category. All you have to do is subtract the prefix from the number 32(As IP addresses is a 32 bit number). Put the result as an exponent of 2 and you will get the number of IPs in that range.
For instance, to find the IP range of "/29" prefix, we subtract The prefix 29 from 32. The result 3 is used as an exponent of 2. Hence, the IP range you get is "2 to the power 3" i.e 8 IPs.
With this method you will be able to calculate any IP range that is provided to you.
The process of subnetting
Suppose an IP address block of 64 addresses is divided into three subnets of 32, 16 and 16 addresses. The mask of the address will the "/26". However, the subnets will have their own subnet masks.
1. First subnet containing 32 addresses will have subnet mask of "/27" (that is 2 to the power 5).
2. Second subnet containing 16 addresses will have subnet mask of "/28" (that is 2 to the power 4).
3. Third subnet containing 16 addresses will have subnet mask of "/28" (that is 2 to the power 4).
Hence, an address block of 64 IP address is divided into three blocks of 32, 16 and 16 addresses each.