We have an application running in the Azure AKS which is accessed from mobile clients by FQDN. We have a lot of client errors about DNS resolution failures.
Users report (and we witnessed it ourselves) that sometimes internet is working as usual but our application fails to connect to the server.
Is it a known problem with FQDNs and Azure in particular? Will having a dedicated domain name help?
FQDN will have some dependency on outbound rules, which don't have any static addresses. Due to the lack of IP on NSG rules, it won't be accessible from the AKS cluster, and as per default behavior, AKS clusters have unrestricted egress.
Below mentioned ports need to be allow from NSG else there will be network issues.
UDP 53 and TCP 443 refer this tutorial for more information