Subnets enable you to allocate specific blocks, or pools, of IP addresses for your Data ONTAP network configuration. This enables you to create LIFs more easily when using the network interface create command, by specifying a subnet name instead of having to specify IP address and network mask values.
A subnet is created within a broadcast domain, and it contains a pool of IP addresses that belong to the same layer 3 subnet. IP addresses in a subnet are allocated to ports in the broadcast domain when LIFs are created. When LIFs are removed, the IP addresses are returned to the subnet pool and are available for future LIFs.
It is recommended that you use subnets because they make the management of IP addresses much easier, and they make the creation of LIFs a simpler process. Additionally, if you specify a gateway when defining a subnet, a default route to that gateway is added automatically to the SVM when a LIF is created using that subnet.