Active Directory | KCC vs ISTG

Focus : Active Directory KCC and ISTG

KCC (Knowledge consistency checker) is responsible for generating site replication toplolgies between domain controllers. KCC runs in each DC of a domain and creates a
connection object for each DC in AD. It is responsible for all intra-site replication.

In case of an inter-site scenario, there will be a bridge-head server to manage site-site replication. Here, the connection objects for the bridge-head servers are created in a seperate way. ISTG (Inter-Site Topology Generator) is responsible for creating connection objects in bridge-head servers. ISTG is nothing but a KCC server(DC), which is responsible for reviewing the inter-site topology and creating inbound replication connection objects as necessary for bridgehead servers in the site in which it resides.The domain controller holding this role may not necessarily also be a bridgehead server.