 For IPv4 networks, the tethering normally works via NAT on the handset's existing data connection, so from the network point of view, there is just one device with a single IPv4 network address, though it is technically possible to attempt to identify multiple machines.On some mobile network operators, this feature is contractually unavailable by default, and may only be activated by paying to add a tethering package to a data plan or choosing a data plan that includes tethering, such as Lycamobile MVNO.This is done primarily because with a computer sharing the network connection, there may well be a substantial increase in the customer's mobile data use, for which the network may not have budgeted in their network design and pricing structures.