Describe the role of the RID Master FSMO role.

• A. The RID Master allocates unique relative IDs to domain controllers for new security principals.
• B. The RID Master updates the AD schema.
• C. The RID Master handles time synchronization.
• D. The RID Master manages DNS records.

Answer: (A)

The key idea here is how uniqueness of identifiers is guaranteed for new objects in a domain. Every user, group, or computer gets a Security Identifier (SID) that combines the domain’s SID with a unique relative ID (RID). The RID Master FSMO role holds the authority to allocate blocks of RIDs to domain controllers within its domain. A DC uses its assigned RID block to stamp new objects with a unique RID, and when that block runs out, it requests more from the RID Master. This centralized allocation prevents two different DCs from issuing the same RID, ensuring every new security principal has a unique SID.

This role is specific to each domain (not forest-wide). It doesn’t update the AD schema—that’s the Schema Master’s job. It doesn’t handle time synchronization—that’s the PDC Emulator’s job. It doesn’t manage DNS records—that falls under DNS (even though AD can use DNS).