In order to test the connectivity to the DB instance, hop on to the RDS Admin Hub or the bastion server that you have. Ensure that the RDS Admin Hub is part of the same VPC as the DB instance subnets. As mentioned earlier, to demonstrate the concept, I considered my RDS Admin Hub as a bastion server as well. Security Group on my RDS Admin hub allows ingress on port 22 for SSH and RDP on port 3389.
RDS allocates a DNS name to each RDS DB instance that we create. In regard to RDS, these DNS names are called endpoints. You need to get the endpoint for the DB instance to establish the connectivity. You can get the endpoint for a specified DB instance by using the following command:
PS C:\> (Get-RDSDBInstance ...
