Subnetting IP and Borrowed Bits

What is subneting?
I would say layperson division a network on multiple subnets in order to improve utilization of all IP addresses that belong to that network.

Let us remember our IP address and the Default (standard) Network Mask.
I will be based on our IP address and the mask, which belongs to the class C private IP address, but in fact as we have seen that the network we received surgery AND-ing (see Figure6)

How to perform Network Subnetting

To execute subneting some networks, we need to borrow a number of host bits and convert them into bits Network.
I hope that you understood and remembered Figure1 and Figure3, in the topics on this blog.

What does subnetting a network?
Suppose that we decided that we should network in a company that will have four subnets (management, accounting, sales and procurement) and each subnet (group office) should have 25 hosts (computers) that use employees of the group, ie. Offices but we have take into account that the number of workers may increase in the future, so we will need another computer.

We are having only one network, ie. Single IP address and containing 254 usable IP addresses. Given that we should total 4 groups with 25 computers now we know it's 100 computers. Each group will plan a maximum of 30 hosts (computers).

What should we be doing that we would fulfill the requirement?
We need to divide (subnetting) our network into four subnets, but each has the option of connecting 25 computers and an IP address can not be duplicated.
How? Well, we'll borrow a certain number of bits from the host portion of the subnet bits and the rest will be used for hosts.

How to borrow bits?

Take for example our network mask

Let us note again, that the fourth octet (byte) called. "Host octet" in the Network Mask. It consists of 8 bits, the figure marked in green (see Figure 7)

Figure 7.

IP Subnetting - binary IP address and mask

From the Network Mask that the fourth octet borrow will be 3 bits ie. first three digits and convert them into units.
Let's go to the next page to continue the tutorial