title: VPC EC2 -> Multi-AZ RDS Unable to connect
body: <p>I have a VPC with a mix of public and private subnets. I wanted DB server, among other things, in the private subnet. For now I have my web servers in 2 public subnets. I spun up a multi-AZ VPC RDS instance into a subnet group that contains 3 dedicated private subnets, each in its own AZ. </p>
  
  <p>Here's the issue. I can connect from one of my public EC2 instances to RDS, but not from the other. I was sharing security groups and ACLs for those two public subnets, so that shouldn't be the issue. As best I can tell, the only thing that was different was that the public EC2 that could connect was in the same AZ as the RDS primary node, while the other EC2 instance was in a different AZ (the same one as the RDS failover). When I ping to the RDS domain name from the non-working public EC2, it resolves the private IP just fine, so that doesn't seem to be the issue...it's as if it just isn't routing correctly. Any ideas?</p>
  
  <p>EDIT: I also tried making the private subnets public by updating the route table, that didn't work either. It really seems to be related to the different AZ.</p>