Can't connect from connected elastic resource to RDS DB

Question

Hello,

I have an EC2 instance. I created an RDS Aurora DB. I connected my EC2 instance and the DB. I can see two security groups, one enabling inbound TCP traffic on port 3306 and one does the same but outbound. They are assigned to the EC2 resp. the DB.

If I ssh onto the EC2 instance and use the mysql command to connect, I get a timeout. So somehow the automatic configuration was wrong but that can't be, can it?

How can I troubleshoot this?

Accepted Answer

If it is a timeout error, you need to make sure that the rules for the RDS and EC2 security groups are correct.  
Also make sure that the network ACLs configured for the subnet also allow the required communications.

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Troubleshooting.html#CHAP_Troubleshooting.Connecting

By the way, would it be possible for you to share with us what settings are in place for the security group?

Can't connect from connected elastic resource to RDS DB

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