A CMDB is rarely a stand-alone application. In order to integrate iTop with the rest of your infrastructure, three powerful mechanisms are available:
Import / Export pages
A scripted Import page available as a web service or from the command line to import or update iTop objects from a CSV file
Data Synchronization enables the federation of data from various sources into iTop:
All these services work on virtually any object in iTop: Devices, Contacts, Tickets, User Accounts…
REST/JSON services are generic services. The APIs are low-level operations (search objects, create/update/delete objects) that will be the building bricks allowing any kind of integration. Furthermore, a custom module can provide higher level operations that will be delivered through this same entry point.