Apart from the elastic IPs already mentioned, two more options: 1) Have a canned VPC-based test server that's off, and only turned on for the test. VPC-based s

Apart from the elastic IPs already mentioned, two more options: 1) Have a canned VPC-based test server that's off, and only turned on for the test. VPC-based servers do not lose their IP addresses between activations (though a single server may not suit you) 2) Use AWS internal DNS - have your vendor product use hostnames rather than IPs (if possible), and when you spin up the new machine for testing, switch it's IP into the hostname on the internal DNS zone. Again, you'll need to be VPC-based to use this. You can destroy the instance between runs with this method.