Why subnetting was introduced

The subnet mask is represented as The router inside the network will have the routing table which will be as follows:.

It is the opposite of Subnetting. In this multiple smaller networks are combined together to form a large network. The routing table contains the entry of a subnet mask for every network. If there are lots of small networks then the size of the routing table increases.

When the router has a big routing table then it takes a lot of time for the router to process the routing table. Supernetting is used to reduce the size of the IP routing table to improve network routing efficiency. All the networks are not suitable for aggregation. There are some rules according to which the network can be aggregated. For any network to be aggregated it should follow three rules.

Example: Suppose we have four small networks with network ID as The last 10 bits are zero. Hence it divisible by the size of the network. Hence, all three conditions are satisfied.

These four networks can be combined to form a supernet. The supernet ID or the network ID for all the four networks will be Supernet Mask is a bit number where all the fixed bits of the network are represented by 1 and the variable part is represented by 0. Overall, there are usable hosts after subnetting. Therefore, it is only necessary to observe the first byte of the IP address to determine its class. Figure 1 shows the decimal value of the first byte for each class. Figure 1 — The class of an IP address can be quickly identified by observing only the first byte.

For example, the Class A network address 0. X cannot be used since it is used to indicate "this" network. Class A address X is reserved for loop back testing. With the host portion of the address, you cannot have an all 0s host, which refers to the network address where the hosts reside. Likewise, you cannot use the all 1s host address because that indicates a broadcast which is a message to all hosts on the network.

Therefore, with any host addressing on either a Class A, B or C network, you lose 2 host addresses. Still with 4 billion possible addresses from a bit address space, you would think there are plenty of addresses even with reserved addresses. The problem is that there was much waste when addresses were originally assigned. For example, a Class A address can handle 16 million hosts per one network ID.

That is an enormous amount of hosts for just one network. Even a Class B address can handle 65 thousand hosts per network ID. A Class C address can handle only hosts per network ID which may be too little for some networks. A scheme was needed to obtain a better balance between network and host assignments and that is called subnetting. If you look at Table 1, you will notice that a class B address uses 14 bits for network addressing and 16 bits for host addressing.

By simply reassigning one of the host bits to a network bit, you would double the number of available network addresses but halve the number of host addresses. Carrying the argument further, move eight of the host bits actually the complete third byte to the network side.

The result is 22 bits for network addressing and eight bits for host addressing which is quite similar to a class C address. These additional network addresses are called subnets and not networks because to the Internet, the original address is still a class B network address but locally the class B network address can be broken down to manageable subnets that function as actual network addresses. Why use subnets? Subnets are interconnected using routers, and routers improve network performance by reducing traffic and minimizing disruption due to broadcast messages.

Large networks become more manageable when subnets are deployed. Table 1 — Address classes define the split between network and host IDs. To create subnets you need a subnet mask that defines which bits will be used to create the new network address out of the bit IP addresses. What do these masks look like? If we start with a basic class A address and do not define any subnets, the mask would look like Only those bits that are set as a 1 will be considered when defining a network address.

In this case, all the bits in the first byte of the IP address will be considered. The natural mask for a class B address is In order to create more network addresses subnets we need to move the mask bits to the right changing 0 bits into 1s in order to convert host bits into network bits. The best way to understand the concept is to use an example. Assume we begin with IP address From Figure 1 we know that this is a class B address with a network address of We do not want 65, hosts on one network but would like to have up to hosts on each subnet.

In order to have hosts on one subnet, we need to have 9 bits of host addressing. Currently, we have 16 bits of host addressing since we possess a class B address. That means that we can reassign 7 of those bits to signify subnet bits. Therefore, the subnet mask would be What is Subnetting, Benefits, and How does it Work? What is Subnetting? What is Subnetting used for? How does Subnetting work?

Benefits of Subnetting Subnetting divides broadcast domains, meaning that traffic is routed efficiently, improving speed and network performance. A subnet mask ensures that traffic remains within its designated subnet. This reduces major congestion and reduces the load imparted on the network. With sub-networks, less distance needs to be traveled by data packets, enhancing network performance. With different subnets within your larger network, you can be more aware of route maps.

These will help you to identify potential threats. With subnets, devices will not be able to access the whole network, meaning that companies can dictate which hardware and users have access to more sensitive data. Network security can be boosted. Sound organization is crucial within large businesses.

This extends to your newtork and routers. With subnetting, companies have full control over their traffic and data packets. Field Engineer has.