Forum Discussion
Two different domains in one Office 365 tenant
Hi,
There can be only one Azure AD Connect instance for a single Azure tenant. This means, you have to use one AAD Connect instance for both companies, if you want to go single tenant.
Azure AD Connect supports connecting multiple forests to a single Azure AD tenant. A server that runs Azure AD Connect does not have to be joined to any domain locally, however, it must be able to access domain controllers in both forests.
In some cases, you can choose to place the Azure AD Connect server in a (DMZ), especially if you do not have a direct network connection to all forests that you would like to include in the synchronization.
If you need more information, you probable should tell what is your goal and how both companies must work together.
Hi,
There can be only one Azure AD Connect instance for a single Azure tenant. This means, you have to use one AAD Connect instance for both companies, if you want to go single tenant.
Azure AD Connect supports connecting multiple forests to a single Azure AD tenant. A server that runs Azure AD Connect does not have to be joined to any domain locally, however, it must be able to access domain controllers in both forests.
In some cases, you can choose to place the Azure AD Connect server in a (DMZ), especially if you do not have a direct network connection to all forests that you would like to include in the synchronization.
If you need more information, you probable should tell what is your goal and how both companies must work together.
If you have two companies as follows:
Company A
Domain: CompanyA.com
Manage and Control their own AD/Exchange forest
Company B
Domain: CompanyB.com
Manage and Control their own AD/Exchange forest
1. Could you migrate these two companies to a single domain (companyC.com)
2. If so, could you run Exchange hybrid until the migration is complete, for example, Joe from Company B is migrated to O365 he now has (joe@companyC.com), but Beth also from Company B has not been migrated, so she's still (beth@companyB.com). Mary from Company A is migrated to O365 so she now has (mary@companyC.com), but Tom also from Company A has not been migrated, so he's still (tom@companyB.com).
3. Could you migrate these two companies to multiple domains under a single tenancy, for example, company A stays companyA.com and company B stays companyB.com in O365, but under a single tenancy structure where administration, billing, and usage are tracked under a single account.
Appreciate your feedback.
1: yes you can
2: this also works fine (i've done this for a customer with 8 different source forests)
3: Microsoft will consider the tenant as a single customer, so you'd have to figure out some way to allocate license costs to the different companies. In addition, administrators will be able to administer ALL users (depending a little on setup), so you'll need some governance on that.
Can u please explain how did this migration ??/
1 and 2 is a no go, since companyC has to be owned by one of the companies and you cannot share UPN domain with multiple forest in a trust..not 100% sure.
3 is yes, CompanyA and company be has trust and communuications to each other. Azure AD connect is setup in the domain that is setup for O365. Same azure ad connect can sync users from the other domain. They will then share same tenancy., this is called multiple forest : https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnect-topologies
Both Domains should have own Exchange on-premise in hybrid setup, since linked mailboxes is not supported in O365.
Hi Off2w0rk, were you able to successfully federate two different domains/companies to one O365 Tenant?
We have it where we have a longterm partnership with a company that has their own O365 Tenant and AD On Prem Environment.
But want to add their domain to our O365 only/ (not our on Prem) From reading this forum, you are able to use Azure AD Connect and add the other company from there?
And they would be able to still access their tenant and our tenant?
Hi Dominik and thanks for prompt reply.
As of now, the main goal is that both company can collaborate with each other in Office 365, but keep internal system seperate.
Not sure if its better they merge on-premise environment or go for the trust and use single AD connect.
thanks!
You are welcome.
From my perspective, if they want to manage their own on-premise Active Directory, use one AAD Connect instance and go to a single Azure tenant.
You can merge it later if you want, this is no problem. Depending of the AAD Connect server placement (domain joined, locally or DMZ) you need no trust relationship.
Make sure both admins from both companies have a good design decision what to sync, merge and which attributes are needed. Then this will be no problem.
Thanks Dominik,
Currently we do not have full overview of their environment and not sure which workload they want to migrate to Office 365.
My guess is that they have AADC joined to domain at CompanyA.
Will they need to create a trust between them for this setup to work?
Thanks!
