2 companies with 2 different AD / Exchange environments coming together as one

Posted on 2007-12-05
Last Modified: 2011-09-20
I have just ben notified that in a little over a month we will be aquiring another company of equal size and thus doubling our physical size however we will be residing in 2 different locations for at least a couple of years until leases etc. run out on office space.  

Currently the surviving company has 1 AD Forest / Exchange server along with other servers like Blackberry, Rightfax, SQL, etc...

The aquired company currently has 1 AD Forest / Exchange server / SQL server.

What is the best way to connect the 2 offices and have them operate as one?

My initial thought is to install a new server at the new location and have it joined to our current domain across a dedicated connection T1 or otherwise between the locations and move the users to our exchange server and the main office having users connect to the exchange server via cached mode etc.. Then the only purpose the server at that location serves is file and print services.

Seems like a lot of expense and work though the more i think about it

Is there a way to have 2 separate AD Forest / Exchange servers in different locatoins have a "trust" between them and operate separately but together?  Seems somewhat like some redundancy that would be nice for our disaster recovery plan.  Could we have the 2 exchange servers in different domains / forest duplicate to one another?  So if one or the other location went down we could pick up and run at the remaining site?

Im sure all of this has been done many different ways over and over.  Any advice anyone has is greatly appreciated
Question by:justingrantiv
LVL 12

Expert Comment

ID: 20412675
You can create a trust between the two domains and access resources on each. You do this from the Active Directory domain's and trusts. You need to be use the DNS of both domains. I would create secondary zones the replicate DNS info on both sites.
LVL 13

Expert Comment

ID: 20412714
the best option will be to create trust betwean the networks.
this way every one have a fast access to there network resources
(mail,files etc) but will have access to resource in the other network with single sign one(SSO).

LVL 12

Expert Comment

ID: 20412724
Oh, make it a two way trust also.
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Author Comment

ID: 20412752
So the domains trust each other / are connected.  Company A's email is located at one office and Company B's at another with Company A responsible for all the sending and receiving over the internet and then to the other "exchange domain"?
LVL 12

Accepted Solution

bhnmi earned 500 total points
ID: 20412781
Both domains will remain independent of each other. You will just be able to have access to resources i.e file services, terminal services and such. Your exchange servers will continue to function normally. You have not made any changes to mx records so email will continue to arrive normally.

Author Comment

ID: 20412799
Both companies are going to be using the original companies domain name so it will need to forward email it receives for users on the other domain to them.  We will also configure the original server to accept email from the old company domain name for a short period of time eventually turning that domain off all together

Expert Comment

ID: 20414556
be carefull that they are some limitations in using Exchange in inter-forest trust configuration. Calendar for instance would only show free/busy.
But it's definitively the way you should go.

Author Comment

ID: 21803597
Ok so this is finally getting ready to happen!  I will be placing a new server at the remote location as a member of Company A's (the original larger company) Domain Structure.  This will server as file / print services at Company B's location.  

I will be doing an exmerge of the users email boxes and importing them into new exchange / active directory accounts on the Exchange server located at Company A's office.  The 2 offices will be connected via a point to point T1.  Users at company B's location will access the exchange server in cached mode to speed that along.  This way we are only maintaining one exchange server license and 1 exchange server for the organization.  

I will then have to move the computers at Company B's location to the Company A domain and get their pc's setup on the "new to them" domain.  I can't just do the Trust between the 2 as part of the Original Company B is going to remain now an does not want the users that are "going" to Company A to have access to their stuff etc....  Large corporate politcal mess!  And there are only about 20 users coming and it is just not worth the fight any longer.  

Do you guys see any holes in this scenario.  They will have full access to the exchange server this way as well and as they want to use voting buttons etc... i thought this would make life much easier.  They also will be coming together in one location in 8 months so at that time it will be seemless.

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