Explanation:
Create two additional sites named Site2 and Site3. Move DC2 to Site2 and DC3 to Site3.
Create an additional site link that contains Site1 and Site2.
Remove Site2 from DEFAULTIPSITELINK.
The Administering Windows Server Hybrid Core Infrastructure guidance for AD DS site design states that each physical location should be mapped to its own Active Directory site so that replication and logon traffic can be controlled and optimized per location. The documentation explains that when you deploy new sites, domain controllers must be moved into the corresponding site containers to ensure intrasite replication uses the local site topology and intersite replication follows site links. It also emphasizes that site links define replication cost, schedule, and frequency between sites; by creating separate site links for the pairs you want to manage, you can independently control replication schedules for those paths. The guides further note that new sites are placed in DEFAULTIPSITELINK by default, and that administrators can create additional site links and then remove a site from DEFAULTIPSITELINK to prevent it from inheriting the default schedule and cost-thereby isolating schedules per site pair. Finally, the KCC/ISTG automatically generate the required connection objects, so you generally should not create manual connection objects unless you have a specific exception. Following these principles: create Site2 and Site3 and move DCs, add a dedicated link (Site1-Site2) to set its own schedule, and remove Site2 from DEFAULTIPSITELINK so Site1-Site2 and Site1-Site3 replication can be controlled independently while minimizing replication interruptions.