ISTG is responsible for creating Active Directory Replication Connection objects for appropriate bridgehead servers within its site. Intersite replication can utilize either RPC over IP or SMTP to convey replication data.

Bridgehead server - A domain controller that is used to send replication information to one or more other sites

DHCP Superscope:

A rage of IP address that span several subnets. The DHCP server can assign these address to clients that are on several subnets.

DHCP Scope:

A range of IP address that the DHCP server can assign to clients that are on one subnet

A stub zone

It is a copy of a zone that contains only those resource records necessary to identify the authoritative Domain Name System (DNS) servers for that zone. A stub zone is used to resolve names between separate DNS namespaces. This type of resolution may be necessary when a corporate merger requires that the DNS servers for two separate DNS namespaces resolve names for clients in both namespaces.

A stub zone consists of: SOA, NS, A Records