What you mean by variable and static subnetting?
Static and Variable Subnetting
Subnetting can be classified into two.
Static Length Subnetting:
If all the subnetworks in a single network use the same subnet mask, it is called as 'Static Length' subnetting.
Variable Length Subnetting:
If the different subnetworks in a single network use different subnet masks, it is called as Variable length subnetting
Advantages of Static Length subnetting:
1)Easy to configure.
2)Native IP routing understands only Static subnetting
Advantages of Variable Length Subnetting:
1)Ip addressess are allocated depending on the number of hosts present in the subnetwork.
2)Available host ip addressess are efficiently used and not wasted