We have a PROD site with 2 networks 1.1.1.X/28 and 10.10.10.X/24.
We have DR site with 2 networks 1.1.1.X/28 and 20.20.20.X/24.
The net 1.1.1.X/28 is not the same (you can't reach host on PROD from DR) as we have MPLS and need to have same network on both sites. On both sites we also have some systems with the same IP in 1.1.1.X/28 network.
We also have 3 MS AD controllers: AD1, AD2 on Prod, and AD3 on DR.
AD3 syncs with AD1. On both DC "Site link" configured through net 10.10.10X and 20.20.20.X respectively.
You can reach systems on net 20 from net 10 and back.
Issue: After a wile (1-5 days), errors regarding KCC (ID 1311 & 1865) occur on AD3 and in tow hours on AD1 & AD2 and synchronization from AD3 to AD1 fails.
Than there is no way to resync zones again automatically.
If using replmon or repladmin manually sync zones from AD1 to AD3, than back sync (AD3>AD1) will work also.
Question: What is wrong and how to make read of KCC error, enabling AD3 sync with AD1 without any errors?