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I wish to designate a second server to authenticate people on the domain when the main server is down for repair, maintainace, updates installation etc. At the moment, the second it goes to reboot, no one can log in, and I have to wait till after hours.

I know this is a gap in my knowledge, and I want to fix this once and for all!

Thank you in advance for any help :)

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up vote 8 down vote accepted

All you need to do is run dcpromo on your second server to add it to the domain. That will make it a second DC, and it will be able to authenticate your users.

That's the simple answer. You should read up on AD because there may be important details that you could miss. If your current DC is a DNS server, the second one should also be a DNS server. Unless you have a specific reason to do otherwise, they should be AD-integrated DNS.

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+1. Though it's not specifically mentioned, it's worth noting that there is no "backup" DC, they are all equal (except for the FSMO roles). In NT4 there was a primary and backups; that is not the case with Active Directory. – Chris S Oct 19 '10 at 12:41
Pretty much. It depends on the amount of downtime. If the first DC is also your only DHCP server, then any machines who's lease expires will probably drop off the network (this behavior may be definable though.) Like I said, there's a lot of reading that you can and should do on AD. Also - like @Chris said, there is no BDC, you'll get a lot of flack for using a term that is no longer operative. There are only DCs. – mfinni Oct 19 '10 at 13:11
+1 I would add that the second server should also be made a Global Catalog server. I generally make all of my DCs GCs – gWaldo Oct 19 '10 at 13:29
@gWaldo - If you have a complex environment with multiple domains, the overhead of a GC can become quite significant ;-) But I agree on making them all GCs in a single domain environment. – Massimo Oct 19 '10 at 15:12
@Guru - watch out with a second DHCP server in a single subnet. It's easily done, but you don't want the ranges to overlap. If you design it wrong, you could have some inconveniences. – mfinni Oct 19 '10 at 15:29

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