The present disclosure discloses methods of controlling network access, NASs and non-transitory machine-readable storage mediums. In an example of the present disclosure, when a terminal comes online for a first time, a NAS obtains a temporary role for a terminal; when receiving an IP address request from the terminal, the NAS requests an IP address for the terminal, wherein a lease for the temporary IP address is a set minimum lease; the NAS forces the terminal to go offline when the portal authentication is successful; when the terminal comes online for a second time, the NAS obtains a service role for the terminal; when receiving an IP address request sent by the terminal at expiry of the lease for the temporary IP address, the NAS requests a service IP address for the terminal, wherein the service IP address belongs to an IP network segment corresponding to the service role.