rat sgsn-mapping       :

Using the rat sgsn-mapping command, you can
control whether the user under the APN is permitted to obtain the RAT type
through the SGSN IP mapping, which is called mapping switch. According to the
table of the mapping between the SGSN IP address segment and the PLMN ID, you
can obtain the PLMN ID of the SGSN, which is also one way to obtain the RAT
type.

By default, the mapping switch is on.