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I know I need to configure the RDS security group to allow connection from EC2 security group.

I have an EC2 instance running in the default security group. so i added the EC2 Security Group to the RDS DB security group. When I try to connect using the mysql client from my EC2 instance it gives me the following error:

ERROR 2003 (HY000): Can't connect to MySQL server on '' (110)

the command i used is:

mysql -udbuser -p

I found this post with the exactly same issue I have, but no one answers

I am able to add CIDR/IP rules and works just fine from my laptop. However, I really need my ec2 instance hook up with my rds. Thanks in advance for any help.

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I have fixed this issue by adding the public ip address of my EC2 server to the DB security group default policy.

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How did you do this? – Amit Erandole Apr 12 '15 at 14:05

To expand on the Yuzhou's answer, and answer Amit's question, you can create a new security group with the corresponding IP range/subnet of your EC2 instances(s). You can use the exact IP(s), or use your VPC's subnet(s) as the range.

Once created, you can right click your RDS instance in the management console and select 'Modify'. From there, you can change the associated security groups.

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