We had a odd issue today related to the security groups in our RDS.
All the sudden, without any changes from our end, our RDS instance's security group stopped working. No server was able to connect to the RDS for 30min.
To workaround the issue, I had to enter the server's specific IP as an IP range in the security group. Once the IP was authorized, the server could connect again.
After awhile, I tried to remove the IP range from the RDS's security group and the sever could still connect. We haven't changed anything in the EC2 groups, so the old security group are set correctly.
Anyone noticed a similar issue?