Here are some of the things that you must configure when promoting a domain controller at a forest with multi sites and multi domains topology.
If this is a new Domain Controller at new site:
a. At Active Directory Sites and Services, create a new site.
b. Create a new subnet and link it to the newly created site.
c. Configure the IP site link for Active Directory replication.
· Promote the Windows Server to become Domain Controller.
· Configure the Domain Controller to become a DNS server – Active Directory Integrated (Domaindnszones).
· Configure the Domain Controller to become a Global Catalog server.
· Configure DNS Forwarders.
· Configure the Domain Controller to be the Authoritative Name Servers in the domain.
· Enable Strict Replication Consistency. (more)
· Disable Windows Scalable Networking Pack Components. (more)
· Change Windows Time Service MaxNegPhaseCorrection and MaxPosPhaseCorrection value to 48 hours. (more)