AWS Client VPN connection problem with RDS in same VPC

Also, if RDS is in multiple VPCs, you will need to set up something like a Transit Gateway to be able to communicate with multiple VPCs. I think the following AWS blog will be helpful for AWS VPC configuration. https://aws.amazon.com/jp/blogs/networking-and-content-delivery/using-aws-client-vpn-to-scale-your-work-from-home-capacity/

Thank you for your answer.

• Inbound rules of my RDS is allowed to receive all traffic from a security group called "A" (source, with all protocol and types). Client VPN endpoint is associated with "A" security group, and "A" security group is permitted for all traffic from default VPC security group.

Client VPN endpoint -> Security Group Associated with: A, Inbound Rule Source, Type, Protocol: default VPC sg, All, All RDS Instance -> Security Group Associated with: B, Inbound Rule Source, Type, Protocol: A, All, All

• "dig" command returns the IP address within VPC CIDR range:

;; ANSWER SECTION: xxxxxx.abcdefghijk.us-west-1.rds.amazonaws.com. 5 IN A 10.0.X.XX

• Public access is set to No for my RDS instance. I actually tested out by setting it to Yes and "dig" command did return a public IP address. I've also tried to query a table within the DB instance, and mysql connection timed out just like you said. Normally when I set a DB instance to public, mysql connection is established but not this case. Can you assume what AWS configuration is prohibiting the connections?