Region and Availability Zone FAQ

Why aren't Regions tightly integrated with each other?

We isolate the Regions from each other to achieve greater fault tolerance, improve stability, and to help prevent issues within one Region from affecting another. To simplify using instances across regions, we provide tools such as ec2-migrate-image and ec2-migrate-manifest.

How do I interact with EC2 in different Regions?

Use the Region-specific service endpoint for the Region you want. To get a list of Regions and their endpoints, use the DescribeRegions API, for example:

PROMPT> ec2-describe-regions

REGION        us-east-1        us-east-1.ec2.amazonaws.com
REGION        eu-west-1        eu-west-1.ec2.amazonaws.com

How do I launch an AMI in another Region?

Simply copy your AMI from its current bucket to a bucket located in the Region where you want to launch the AMI and register the AMI. For example, to launch a US-based AMI in the EU Region, you have to copy the AMI to an Amazon S3 bucket that was created with an EU location constraint. After the AMI is copied, you must register the AMI and use the obtained AMI ID for launches in the new Region.

Also, make sure to give read access to the bucket, image manifest, and image parts to ec2-bundled-images@amazon.com for Windows AMIs, and za-team@amazon.com for Linux AMIs.

What tools are available to help migrate my AMIs to a new Region?

The API Tools contain a new command called ec2-migrate-image. It is designed to help migrate AMIs to a new Region. Run ec2-migrate-image --help for more details.

Can I use the same SSH key pair across Regions?

No. You must create a separate SSH key pair for each Region.

	Note
	This is the key pair used for SSH connections to the instance. Your AWS Account ID credentials are global and you use them for all Regions.

How do I launch an Amazon EBS volume from a snapshot across Regions?

At this time, snapshots cannot be copied across Regions. However, data on Amazon EBS volumes can be copied across Regions out of band, For example, you can run an instance in the Region with the source volume, run an instance in the destination Region with a new volume attached, and use rsync or some other file copy mechanism to copy data.

If I make service calls to the ec2.amazonaws.com service endpoint, where will my instances launch?

They will launch in the original Amazon EC2 us-east-1.ec2.amazonaws.com Region.

Can instances use group-based firewall rules across Regions?

No. Group-based firewall rules only work within a Region. If you need instances to communicate with each other across Regions, you should use CIDR based firewall rules. To simplify IP address management, you can use firewall rules in combination with Elastic IP addresses.

	Note
	Because inter-Region traffic crosses the public Internet, encrypt all sensitive data.

How do I use the command line tools with multiple Regions?

By default, the command line tools use the original us-east-1.ec2.amazonaws.com Region. To specify a different Region, see Region and Availability Zone Concepts.

What is the cost for data transfer between Regions?

Data transferred from one Region to another is charged at both sides at the Internet data transfer rate.

Can I assume that my Availability Zone us-east-1a is the same location as someone else's Availability Zone us-east-1a?

No. Currently, we do not support cross-account proximity. Each account's availability zones are independent. For example, the us-east-1a Availability Zone for one account might be in a different location than for another account.

How can I make sure that I am in the same Availability Zone as another developer?

We do not currently support the ability to coordinate availability groups between developer accounts. We are seeking customer feedback to understand the types of use cases for proximity control between accounts. We will use this feedback to determine how and when we might provide Availability Zone control between accounts.

Regional data transfer seems like such a small charge, why are you complicating my bill with this?

We anticipate that for most common use cases, Regional data transfer will only constitute a very small portion of your monthly usage charges. There are valid use cases that involve moving large amounts of data between Availability Zones. In these cases, the Regional data transfer can be a significant cost.

We try to enable as many use cases as possible while charging you only for what you use. Because of the large potential differences in the way developers could use Regional data transfer, we think it is appropriate to break this cost out rather than amortize it across other charges.

If I have two instances in different Availability Zones, how will I be charged for Regional data transfer?

Each instance is charged for its data in and data out. Therefore, if data is transferred between these two instances, it is charged out for the first instance and in for the second instance.

If I transfer data between Availability Zones using public IP addresses, will I be charged twice for Regional data transfer (once because it crosses Availability Zones, and once because I use public IP addresses)?

No. Regional data transfer rates apply if at least one of the following cases is true, but are only charged once for a given instance even if both are true:

The other instance is in a different Availability Zone, regardless of which type of address is used
Public or Elastic IP addresses are used, regardless of which zone the other instance is in

Why are my Amazon EC2 resources not visible in the EU Region?

Amazon EC2 Regions are isolated from each other. Resources such as SSH key pairs, security groups, and AMIs, are not replicated between Regions. For more information, see Resources.