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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.

pierre
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2 Answers2

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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.

joeqwerty
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EDITED:

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.

Craig Tullis
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