A connection initiated by a system or operator back to the original caller. In legacy remote access and secure networks, a server drops the initial incoming connection and dials a pre-authorized number to ensure the user is calling from a trusted location. In customer service, it is an automated feature that holds a caller's place in the queue and rings them when an agent is free.
Heard on the job
Configure the dial-in server for strict callback so nobody can access the management VLAN from an unknown number.