It is a mask utilized for determining the source of the subnet of an IP address. Basically, IP addresses comprise of two components. It has a network address and the host address. This means, if the IP address is 150.343.858.089 and it is a part of Class B network, the first two sets of numbers listed such as 150.343 would represent the Class B network address. As for the second two set of numbers, 858.089, they can identify the host of the network.
Why is subnetting important?
It enables the network administrator further divide the host section of the address into two to more subnets. It will be easier to determine the part of the host address that is actually reserved to the particular subnet.
What is a subnet or a subnetwork?
It pertains to visible subdivisions of an IP network. As mentioned earlier, "subnetting" would mean the division of a network in various subnetworks.
Understanding Subnets and Subnet Masks
Keep in mind the all computers do belong a subnet and these have addresses having identical, common and most significant bit-group in the IP address. This causes a logical division of the IP address to 2 fields. One field would be for the network or the routing prefix. The other field would be the "rest field". This "rest field" is the specific identifier for the network interface or computer.
For the routing prefix, it is always expressed in CDIR notation. This means, it is written as the 1st address of a network and then followed by the prefix's bit-length. It is just separated by a slash character.
When it comes to the traffic between subnetworks, these can be interchanged through a special gateway computer known as "routers". These routers represent physical or logical borders between subnets.
Advantages of subnetting can vary with every deployment scenario. In the case of address allocation architecture of the Net through the use of CIDR or Classless Inter-Domain Routing as well as in large organization, it is essential to efficiently allocate address space. As a matter of fact, it can also improve routing efficiency. It can also be convenient in network management, especially if subnetworks are controlled administratively by distinct entities in bigger organizations.
These subnets can be logically arranged in hierarchical architecture. This is done by partitioning the network address space of an organization into a "tree-like routing structure".
