Troubleshooting AWS RDS and EC2 Connection Errors

Correct Answers: A and B.

The AWS Documentation mentions the following.

When you cannot connect to a DB instance, the following are common causes.

· The access rules enforced by your local firewall and the ingress IP addresses you authorized to access your DB instance in the instance's security group are not in sync.

The problem is most likely the ingress rules in your security group.

By default, DB instances do not allow access; access is granted through a security group.

To grant access, you must create your own security group with specific ingress and egress rules for your situation.

· The port you specified when you created the DB instance cannot be used to send or receive communications due to your local firewall restrictions.

In this case, check with your network administrator to determine if your network allows the specified port to be used for inbound and outbound communication.

· Your DB instance is still being created and is not yet available.

Depending on the size of your DB instance, it can take up to 20 minutes before an instance is available.

Option C is incorrect because the connection comes from the application to the database.

As the Security group is stateful, only the ingress rule needs to allow the connection.

Option D is incorrect because if the database is stopped, you cannot connect to the bastion host's database.

For more information on troubleshooting connecting to AWS RDS, please refer to the below URL-

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

Based on the information provided, there could be several possible issues causing the error message "Error connecting to database" when attempting to connect to an RDS Instance from an EC2 instance. However, we can rule out option D, which suggests that the database is stopped, since it was confirmed that a connection can be made from a bastion host in a public subnet via the AWS Console.

So, let's take a closer look at the remaining options:

A. The application is using the wrong port number in the connection string. The connection string is used to specify the server, port, and other parameters required for the application to connect to the database. If the application is using the wrong port number in the connection string, it won't be able to connect to the database. In this case, it's worth checking the configuration of the application and ensuring that it's using the correct port number for the RDS instance.

B. The database server has the wrong ingress Security group rule for the web server. The ingress security group rule controls the inbound traffic to the RDS instance. If the RDS instance has the wrong ingress security group rule for the web server, the web server won't be able to connect to the RDS instance. In this case, it's worth checking the security group rules associated with the RDS instance and ensuring that the web server is allowed to connect to the RDS instance.

C. The database server has the wrong egress Security group rule for the web server. The egress security group rule controls the outbound traffic from the RDS instance. If the RDS instance has the wrong egress security group rule for the web server, the web server won't be able to connect to the RDS instance. In this case, it's worth checking the security group rules associated with the RDS instance and ensuring that the RDS instance is allowed to send traffic back to the web server.

To summarize, the two possible issues that could be causing the error message when attempting to connect to an RDS instance from an EC2 instance are:

• The application is using the wrong port number in the connection string.
• The database server has the wrong ingress security group rule for the web server.

It's worth noting that there could be other potential causes of the error message, but without further information, it's difficult to determine what they might be.