How to promote a BDC to a PDC automatic

I have 2 servers a PDC and a BDC.  I want to mirror both serves.

Can anyone please help.

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KCTSConnect With a Mentor Commented:
wmeeraz is quite correct. While there is still a PDC Emulator - as much as for backwards compatibility as anything else, there has been to such thing as a BDC since Windows NT4. Since Windows 2000 all DCs are writeable and the multi-master database model means than all DCs can u[date each other and there is no sinle read/write copy.

By default the first S that you create will howerver have som so called FSMO roles, and will be both a glogal catalog server and DNS server.

If you want redunancy then after promoting a second machine to be a domain controller you need to:-

From the command line promote the new machine to a domain controller with the DCPROMO command from the command line - Select Additional Domain Controller in an existing Domain

Once Active Directory is installed then to make the new machine a global catalog server, go to Administrative Tools, Active Directory Sites and Services, Expand ,Sites, Default first site and Servers. Right click on the new server and select properties and tick the"Global Catalog" checkbox. (Global catalog is essential for logon as it needs to be queried to establish Universal Group Membership)

Install DNS on the new server. Assuming that you were using Active Directory Integrated DNS on the first Domain Controller, DNS will automatically replicate to the new domain controller along with Active Directory.

If you are using DHCP you should spread this across the domain controllers, In a simple single domain this is easiest done by setting up DHCP on the second Domain controller and using a scope on the same network that does not overlap with the existing scope on the other Domain Controller. Dont forget to set the default gateway (router) and DNS Servers. Talking of which all the clients (and the domain controllers themselves) need to have their Preferred DNS server set to one domain controller, and the Alternate DNS to the other, that way if one of the DNS Servers fails, the clients will automatically use the other,

Both Domain Controllers by this point will have Active Directory, Global Catalog, DNS and DHCP. and the domain could function for a considerable time at least should any one of them fail. However for a fully robust system you need to be aware that the first domain controller that existed will by default hold the FSMO Roles. There are five of these roles that are held on a single server and are essential for the functioning of the network. If the second Domain Controller fails, then no problem as the FSMO roles are on the first Domain Controller. However if you intent to function with the second Domain Controller only, then the roles need to be moved to the Second Domain Controller. Ideally if this is a planned event you should cleanly transfer the FSMO roles (see

In an unplanned emergency the FSMO roles can be seized (see but this should only be done if the failed DC is never coming back - in which case you also need to clean up the failed DC first (see

If this is server 2003, there is no notion of BDC & PDC, they are all domain controllers. Is it just the roles you are inquiring about? and when you say mirror, are you just looking at redundancy with the roles?
Alan Huseyin KayahanCommented:
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