Active Directory: Replication Problems Between Domain Controllers

What you’ll notice: Slow updates across DCs, errors when running repadmin /replsummary, Event IDs 1311 or 1988.

Why it happens:

• DNS is not set up correctly
• Site links are missing or incorrect
• Firewalls blocking important ports

How to fix it:

• Check that all DCs point to the correct internal DNS
• Use tools like repadmin and dcdiag
• Open required ports: RPC (135), LDAP (389)
• Restart services: Netlogon and NTDS