Amazon separates servers from IP addresses

Amazon Web Services has released a product that separates its rentable servers — 'instances' — from their IP addresses.

The Elastic Network Interface (ENI) product was released by Amazon on Wednesday. It only works with instances that sit inside Amazon Web Services's Virtual Private Cloud (VPC) product, which was launched in August 2009.

"Today we are adding additional flexibility to EC2 instances running in the Virtual Private Cloud," Amazon wrote in a blog post. "First, we are teasing apart the IP addresses (and important attributes associated with them) from the EC2 instances and calling the resulting entity an ENI... Second, we are giving you the ability to create additional ENIs, and to attach a second ENI to an instance."

ENIs are independent from the instances they point to, so this means that people can create high-availability cloud infrastructures relatively cheaply by spinning up a single instance with an ENI and, if it fails, reassigning the ENI to the new instance. If this approach is used, "traffic flow will resume within a few seconds," Amazon said.

The product can also be applied to instances running software that is tied to a specific MAC address, as the MAC address can be tied to the ENI's IP address, making the software independent of the underlying server. This means people can choose to rent more powerful instances if they need to, without having to buy another commercial licence.

ENIs can be created and managed via the Amazon Web Services Management Console. They can be attached to existing instances as well.