Azzure Front Door Premium to Premium Domain Migration

Hi Tom Kompare,

Thanks for reaching out in Microsoft Q&A forum,

We need to move domains from a Front Door Premium to a different Front Door Premium in a different subscription. Is there any way to do this with either no downtime, or are there best practices to minimize downtime? How long will the maintenance window need to be if zero downtime?

Migrating a custom domain between two Azure Front Door Premium instances that reside in different subscriptions requires careful planning because Azure does not support directly transferring a domain from one Front Door profile to another.

A custom domain can only be associated with a single Front Door profile at a time. Because of this limitation, the domain must first be removed from the source profile before it can be attached to the target profile.

• Lower DNS TTL early: Set your custom domain's TTL to 300 seconds (5 minutes) at least 24-48 hours before cutover. This ensures global DNS changes propagate quickly once you update the CNAME record to point to the new Front Door endpoint.
• Pre-configure target profile: Build out the new Front Door Premium completely origin groups, routes, WAF policies, rules engine before the migration window. The profile must be production-ready to serve traffic immediately upon domain attachment.​
• TXT pre-validation: Add AFDVERIFY TXT records to your DNS while the domain remains on the source Front Door. This skips validation delays and speeds certificate provisioning (1-10 minutes typical for Premium managed certs).

After the domain is added to the new profile, managed certificate provisioning and configuration propagation will occur across the Front Door edge network. This usually completes within a few minutes.

Although true zero downtime cannot be guaranteed because the domain must briefly detach from the original profile, the interruption is typically very short when these preparations are followed.

Update:

As discussed through offline and from PG update,

If the AFD is empty, you can delete the empty AFD and move the entire AFD to the other subscription if they want to without downtime

look here 

Azure Front Door frequently asked questions (FAQ) | Microsoft Learn  

Is it possible to migrate a domain from one Front Door endpoint to another Front Door endpoint without any downtime?

At this time, we don't offer the option to move domains from one endpoint to another without any interruption in service. You need to plan for some downtime if you want to migrate your domains to a different endpoint. 

Reference:

• How to add a custom domain - Azure Front Door | Microsoft Learn
• Azure Front Door frequently asked questions (FAQ) | Microsoft Learn

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