Question

We have several servers running inside an Amazon VPC. The server private IP addresses periodically change as we upgrade them, etc and so we wanted to use the external IP addresses (EIPs) assigned to those as the points of connection for mysql and other services. I read that traffic directed towards external IPs of two computers on the same network is automatically routed to the internal network. True and great!

The only complication seems to be where a server needs to communicate to mysql or other services on its own external IP. If the security settings are wide open, then this works fine. But as soon as this is not the case – while other computers in the same security group can connect to each others external IPs without problem, it seems that a server cannot connect to itself without problems.

Any thoughts on solving this without resorting to having to reference the private internal ip addresses of instances in the VPC?

Answer 1

You might try some of the following:

• DNS. You can use Route 53 (or any other DNS provider) to create DNS records that point to your current IP address of an instance.
• Secondary Elastic Network Interfaces can be moved from one instance to another so after an upgrade you could just move the NIC to the new production instance without changing any IP addresses.