How to sync on-premises domain with Azure AD when on-premises has .local suffix

Question

In order to sync an on-premises domain to Azure, I believe I need to do the following.

1. Add custom domain name matching my on-premises domain name
2. Verify this domain name
3. Run AD Sync from a computer joined to my on-premises domain

When running the domain sync, it indicates the mydomain.local has not been verified which is required to be able to sign-in to Azure AD with on-premises credentials.

Since that is a DNS name that is only known by the on-premises domain due to the .local suffix, how can we verify it?

Answer 1

When running the domain sync, it indicates the mydomain.local has not been verified which is required to be able to sign-in to Azure AD with on-premises credentials.

Due to your local domain is a private domain, so you cannot verify it with Azure AD. The Azure AD can only verify the domain that registered in public.

You need to register a new domain in public, and then use this new domain to verify with the Azure AD. Once the domain verified, you should add it to your local DNS, and by this, you not need change you .local suffix, then when syncing to Azure AD, the local domain can be matched with Azure AD.