Cool Subnetting Tricks with Variable Length Subnet Mask
Benefits of VLSM VLSM provides the ability to subnet an already subnetted network address. The benefits that arise from this behavior include: Efficient use of IP addresses: IP addresses are allocated according to the host space requirement of each subnet. IP addresses are not wasted; for example, a Class C network of 192.168.10.0 and a mask of 255.255.255.224 (/27) allows you to have eight subnets, each with 32 IP addresses (30 of which could be assigned to devices). What if we had a few WAN links in our network (WAN links need only one IP address on each side, hence a total of two IP addresses per WAN link are needed). Without VLSM that would be impossible. With VLSM we can subnet one of the subnets, 192.168.10.32, into smaller subnets with a mask of 255.255.255.252 (/30). This way we end up with eight subnets with only two available hosts each that we could use on the WAN links. The /30 subnets created are: 192.168.10.32/30, 192.168.10.36/30, 192.168.10.40/30,