Two way trust between Azure AD P1 and on prem AD

Question

Hi,

I have company A that has only a footprint in M365 cloud with an Azure P1 ad license.
I have company B that has AD on prem en M365 (AADConnect, ExchangeOnline,...)

Company A wants to have a ad two way trust with Company B, so they can use the same account and have access on prem and in the cloud of Company B.

In the olden days you would have AD on prem and setup a two way trust between the two AD's, use some AD groups to organize the permissions.
But company A is cloud only, so is it possible to do this connection?

Kind regards,

Tom

Answer 1

Azure AD (Azure P1) is not an Active Directory environment and does not native support forest/domain trusts. The only way to have a two-way trust would be to introduce Active Directory to company A.

However, you can have a one-way trust by introducing Azure Active Directory Domain Services to Company A.

https://learn.microsoft.com/en-us/azure/active-directory-domain-services/overview

https://learn.microsoft.com/en-us/azure/active-directory-domain-services/tutorial-create-forest-trust