Duplicate Computer on Network
Another computer with the same name exists on the network.
Two computers must never run the same Active Directory database at the same time. This can cause serious confusion on your network and can create errors in AD replication.
To prevent this problem, when you run U-Move on the destination computer it will carefully scan your network to see if the source computer is also connected with the same name. U-Move will scan DNS, WINS, NETBIOS, and the Network Neighborhood in order to try to find the source computer.
If U-Move finds the source computer it will warn you and refuse to proceed.
When cloning AD, the new DC must never 'see' the original DC on the same network. If you replacing the old domain controller via cloning, you must first permanently disconnect the old DC from the network and retire it.
When upgrading AD, U-Move will check to see whether the name or the IP address of the new computer clashes with the old computer. If there is a conflict it warn you and refuse to proceed.
Changing the IP address will not work
When cloning AD, even if you change the IP address and the computer name, the old and new computers still cannot coexist. You cannot clone a domain controller merely by changing the IP address. This is because the cloned DC has the same security identity as the old DC (identical Machine ID), which is fixed for the life of the computer. Changing the computer name will also not work.
For this reason, the computers in your production network should never see both cloned DCs simultaneously. Otherwise the two AD databases will slowly diverge over time and become inconsistent.
Renaming the domain will not work
Renaming the domain (e.g., from MyDomain1.local to MyDomain2.local) will not work either. The two domain names still share the same security identity (SID) and therefore still belong to the same AD domain.
How To Fix This Error
If you are doing a test move, the new cloned DC must be installed in an isolated test lab that has no visible network connection to any of the original DCs or client desktop computers on the production network. For example, load the test DC in a virtual machine (VM) that is running inside a virtual network that has no connection to the real network.
If you are replacing the old DC, permanently disconnect the old DC from the network and retire it.
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