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I'm having some trouble connecting to a MySQL 5.1 server on an RDS instance on AWS from my laptop.

The detailed description of the problem is here: https://forums.aws.amazon.com/thread.jspa?messageID=323397

In short: I have 2 MySQL servers, both with the same db configuration and firewall (security group) configuration. One of them works fine: I can connect to it from my EC2 instances (ie, from inside the AWS cloud) and from my laptop. The other one doesn't: I can connect from my EC2 instances but not from my laptop.

The symptom: a connection attempt from my laptop just hangs, and then times out, as if there was a firewall blocking me (ie, silently dropping my SYN packets).

I must say that everything has been working fine for a very long time, and this problem began suddenly, 3 days ago, without any modifications to DB parameters or the security groups.

My current analysis of the situation:

  • The firewall (ie, security group) cannot be the problem: both MySQL servers share the same firewall configuration -- I can connect to one of them but not to the other. Later on, I even added a rule to allow inbound connections from 0.0.0.0/0 (ie, I turned off the firewall), and nothing. Oh, I also created a new, fresh security group and changed this instance's SG to the new one (to which I first added my ip address, and then 0.0.0.0/0) but still nothing.
  • The credentials cannot be the problem: I use the same from my laptop and from my EC2 instances -- and the user (which is what Amazon calls master user), in the database, has a host of '%'.
  • MySQL is not blocking my IP due to, say, too many failed connection attemps: I've FLUSH HOSTS on the database, and also I tried to connect using many different source IP addresses, even from all around the world through a VPN proxy service.

What could I be missing?

I'm asking here because it's been about 36 hours since I've posted on AWS forums but got no answer at all over there... someone here might have a solution!

Any input is really appreciated, I'm out of ideas. Thanks!

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Do you have something like SELinux or Apparmor? Did you try to shutdown mysqld and place another server there, like "nc -l -p 3306"? Also check any packages that you may have installed around that time –  golimar Mar 1 '12 at 7:59
    
golimar, this is an RDS instance: it is a database server completely managed by Amazon. All we can do is use a web interface (or a CLI) to change MySQL parameters, change Security Group (ie, the firewall) parameters and reboot the machine. There's no way to "ssh into the server" (the whole idea is that they should take care of everything and make it run smoothly), and, to be frank, I have no idea what the host system is, or what kind of packages it has installed. Anyways, thanks for the input! –  Bruno Reis Mar 1 '12 at 8:29

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