Limiting mobility between networks based on cellID

Restricting mobility between networks by identifying and rejecting incoming mobility events (e.g. handovers) from unknown cell sites based on a cellID included in a handover request. Core network nodes e.g. MME, AMF, SMF, can detect and reject the incoming mobility events by comparing Cell ID with a white list or referring to a database. This improves over current 3GPP specifications and network vendor implementations that support restriction policies on the source but not on the target.