@Balachandar Ramalingam I understand you are move you existing app service to an external ASE and wish to understand if it will still work with your Azure FrontDoor as your Layer-7 load balancer.
I do not think there will be any issue here:
- As an External ASE has a public VIP, which means that all HTTP/HTTPS traffic to the apps in the ASE hits an internet-accessible IP address.
- For Azure Front Door the origin must have a public IP or a DNS hostname that can be resolved publicly.
So, you should not face any issue in adding the External ASE domain name or public IP address as an origin to your front door. Although it is highly recommended to test this scenario in Test environment first as you have will have to make changes to your origin in your front door more details here.
Reference:
Hope this helps! Please let me know if you have any questions. Thank you!
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