Does anyone know if this possible?

We have an SBS 2008 domain controller on our network. We also now have a Windows Server 2012 Essentials server. Ideally I'd have this join the existing domain, but I know this is not possible in this version.

Could I setup the Win 2012 machine as an independent domain, on a different subnet, and bridge the two LANs?

Would this cause any issues related to their being two domain controllers running? I know ordinarily having two (essentially SBS) servers on the same network would cause one to reboot.

  • There are just... so many things wrong with this, but let's start with the meaning of the word "domain," and the fact that there's no such thing as a PDC anymore (it's PDC Emulator, which is a FSMO role, and for which only one can exist per domain). If you can fix that up, you might get a decent answer to your question. – HopelessN00b Mar 13 '14 at 14:11
  • It's a domain controller; and it's the primary one :S if the terminology is out of fashion I can't see how that has a bearing on the ability to answer: SBS, as stated, can only have one of these. I have changed the acronym, nonetheless.. – pierre Mar 13 '14 at 14:29
  • I was actually referring mainly to your apparent confusion over what an Active Directory domain is, rather than that... but... well, I guess we'll see. – HopelessN00b Mar 13 '14 at 14:32

This is where I think a lot of people get this wrong. When you hear or read There can only be one SBS server on the network what you should understand is that they're using the term network in the colloquial sense. What they mean is There can only be one SBS server joined to, and a member of, the same Active Directory domain.

You can have, and I've seen many times, multiple Active Directory domains (with and without SBS) sharing the same physical network and in some cases using the same layer 3 address space.

There are really only two issues to watch for in this scenario:

  1. DHCP. If SBS detects another DHCP server on the network it will shut it's DHCP service down.

  2. IP addressing. Making sure that you're not using the same ip addresses for hosts in each domain, and inadvertently creating ip address conflicts, becomes more of a challenge.

  • Thank you. The intent was to have two domains, totally distinct, but have them on the same subnet. From what you describe; this should work. – pierre Mar 13 '14 at 15:35
  • 1
    It should, bearing in mind the caveats I listed in my answer. – joeqwerty Mar 13 '14 at 15:36


I didn't pay close enough attention or clarify; you cannot join a Windows 2012 Essentials server to an existing SBS domain. Small Business Server is basically gone as a product, and Windows Server (2012) Essentials is its successor. Essentials is not Small Business Server. Many (most) of the classic Small Business Server features have been removed. But the same "only one SBS Server in an Active Directory domain" rule applies.

So in that vein, an Essentials server cannot be joined to an existing SBS Active Directory domain, in the same general sense that you cannot have two SBS servers in the same Active Directory domain.

Sorry for the mislead.

You could of course join a regular Server 2012 machine to the existing Small Business Server Active Directory instance, as a member server.

My other points remain valid. Two or more Active Directory domains can happily co-exist in different IP subnets (VLANs, separate switches, whatever). The biggest issue with trying to put them on the same subnet (in the same layer 2 broadcast domain) will be DHCP contention.

What do you mean by "bridge" the two LANs, though? You could configure a router (or a switch with Layer 3 capability) to forward packets between the two networks, making communication possible while still segregating broadcast traffic, which automatically solves the DHCP problems.

You could also configure DNS in each network to forward queries to the other, so that machines in one AD domain could find machines in the other. And of course member machines in either subnet could be members of either AD domain and happily talk to their respective Active Directory servers across the router. But you would definitely have separate logical networks at least from an Active Directory standpoint. A user in one AD domain would not be authenticated in the other (unless they had accounts in both with the same account name and password, but that's a different rabbit hole).

You can create trust relationships between standard AD domains, but not with Small Business Server (that's one of the baked-in limitations of SBS). Etc.

  • At least at present, this is unfortunately incorrect. He cannot join the Server 2012 Essentials server to the existing domain, because that's one the restrictions on Server 2012 Essentials, which is basically the new name for the SBS line of server products. Also, you've got a wall-of-text thing going on that would be nice if you fixed. – HopelessN00b Mar 13 '14 at 15:53
  • Ah... right, because Server 2012 Essentials is the de-facto successor to SBS, even though it's really sort of watered down in comparison since it's Microsoft's answer to pushing you off your own local Exchange server into their cloud offerings. You're right. Thanks. – Craig Mar 13 '14 at 15:58
  • But nobody should make the mistake of thinking that Server 2012 Essentials is actually Small Business Server. Small Business Server has gone away... – Craig Mar 13 '14 at 16:01

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