New-MgDomainFederationConfiguration is failing with 409

Hello @Ladislav Čapka,

Thank you for posting your query on Microsoft Q&A.

Based on your description, it seems you are trying to federate your domain with Google IDP by running a PowerShell command. I hope you are referring to the following documents:

Configure Microsoft Entra ID as a Service Provider (SP) for Google Workspace

Set up single sign-on (SSO) between Google Workspace and Office

Regarding the error: New-MgDomainFederationConfiguration_CreateExpanded: Resource already exists. Status: 409 (Conflict) ErrorCode: Request_MultipleObjectsWithSameKeyValue,

The error Request_MultipleObjectsWithSameKeyValue typically indicates that the IssuerURI provided in the command is already in use, either in another domain within your tenant or in a different tenant. IssuerURIs must be globally unique.

The IssuerID is the identifier set by the Identity Provider (Google in this case) in the token passed to Entra. Entra uses this IssuerID to locate the tenant-domain and retrieve the signing certificates required for signature validation. To address this, you will need to modify the Identity Provider's configuration to issue a custom IssuerID. Check with Google to generate a custom IssuerID. After making this adjustment to the IssuerURI, you should be able to proceed with the federation.

If your domain status is currently set to Federated, you can convert it to Managed using the following PowerShell commands:

Connect-MGGraph -Scopes "Domain.ReadWrite.All", "Directory.AccessAsUser.All"
Update-MgDomain -DomainId <domain name> -AuthenticationType "Managed"
Get-MgDomain -DomainId yourdomain.com

For detailed steps, refer to this document: Migrate from Federation to Cloud Authentication.

Once the domain is in a Managed state, re-run the PowerShell command with a unique IssuerID and monitor the results. If the issue persists or you encounter additional errors, feel free to share the details for further assistance.

I hope this information is helpful. Please feel free to reach out if you have any further questions.

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Thanks,
Raja Pothuraju.

We had the same issue. Microsoft support had no idea what was going on, but the issue results from:

1. A bug in the Microsoft Graph API which marks a domain as federated prior to a federation configuration being made. When the configuration is invalid when the underlying internal API call is made, there is no failsafe. This makes it impossible for the Graph API to ever update, delete or
2. Entra ID federation identifies a configuration by the entityID. With Google Workspace, this is always the same, as it's linked to your tenant.

Because of this, you may find your config worked for one domain, but running it again resulted in this 409 error:

New-MgDomainFederationConfiguration_CreateExpanded: Resource already exists.

Status: 409 (Conflict)
ErrorCode: Request_MultipleObjectsWithSameKeyValue
Date: 2024-12-23T15:13:51

If you cannot use Update-MgDomain -DomainId <domain name> -AuthenticationType "Managed" to reset the configuration (due to the bug in the Graph API), use Windows Powershell (not Powershell core) and run:

Install-Module MSOnline
Connect-MsolService
Set-MsolDomainAuthentication -DomainName <domain> -Authentication Managed

To fix the issue:
Open your SAML configuration XML file and find every URL. Change the last part of the string for each subsequent domain: &a
For Google Workspace, it might look like this:

https://accounts.google.com/o/saml2?idpid=xxxxxxxx

Then, append &a to the end, like this (or any string you like)

https://accounts.google.com/o/saml2?idpid=xxxxxxxx&a

This will resolve the duplication issue, and you'll be able to create the configuration.

Hope this helped.