With fixed-length subnet masking (FLSM) the same quantity of addresses has allotted for every subnet. It’s a sequence of figures of constant length that streamlines packet routing inside the subnets of the proprietary network. If all of the sub-network has similar needs for the amount of hosts, these fixed-size address blocks could be enough.
But, most often that isn’t the situation. Fixed-length subnet masking (FLSM) also called conventional subnetting. The Standard Subnetting method causes wastes of IP Addresses. Since the same quantity of addresses allotted to every sub-network the requirement isn’t similar.
The topology proven in Figure 1 above requires 5 subnets, one for that four LANs, and something for WAN link between routers. Using traditional subnetting using the address of 130.10../23, we are able to borrow w bit in the third octet and a pair of bits in the last octet from the host portion to satisfy the subnet necessity of 5 subnets.
As proven in Figure 2, borrowing 3 bits creates 8 subnets leaving 6 host bits with 62 functional hosts per subnet. This plan of action produces the preferred subnets and meets the host demand for the biggest LAN.
Though this traditional subnetting meets the needs from the largest LAN and divides the address space into enough quantity of subnets, Therefore it leads to the main waste of unused addresses.
For instance, 3 addresses have needed for WAN subnet, But each subnet has 62 functional addresses, you will find 60 unused addresses obtainable in this subnets. This limits the development from the network by reduction of the entire quantity of subnets available.
This incompetent utilization of addresses may be the feature of traditional subnetting. Traditional subnetting plan for this scenario isn’t professional in addition to a filled with waste. To prevent a total waste of Ip subnetting a subnet, or using Variable Length Subnet Mask (VLSM), was design. Figure 3 Show the cake chart for that above table of fixed-length subnet masking (FLSM).
Applying a conventional subnetting plan for this scenario may not be efficient and it is inefficient. Really, this situation is a great model for showing the way we may use subnetting a subnet to maximise address utilization. Subnetting a subnet, or utilizing a variable-length subnet mask (VLSM), to save lots of addresses.