switching hub (n)~ A central network device (multiport hub) that forwards packets to specific ports rather than as in conventional hubs broadcasting every packet to every port. In this way the connections between ports deliver the full bandwidth available. switchover (n)~ An administrator-initiated action in which one or more passive copies of the mailbox database are being activated and designated as the active copy. An administrator can perform a database switchover which is the activation of a single mailbox database copy or an administrator can perform a server switchover which is the activation of multiple mailbox database copies.