How do I host a public domain if I have to DHCP an IP address?

You can use a dynamic DNS service, such as DynDNS or ZoneEdit. Alternatively, you can map an elastic IP address to your instance and avoid the propagation delays possible with a dynamic DNS solution.

Why do I get an internal (RFC 1918) IP address when I look up a DNS name that I expect to map to my instance's external IP address?

The Amazon EC2 DNS servers return the internal IP address when asked about an instance's public DNS name. In this way, DNS lookups that would resolve to a public Amazon EC2 IP address will be translated to the correct internal IP address. This only works when using the Amazon EC2 DNS servers from an Amazon EC2 instance.

Why is Amazon EC2 Using NAT?

Public IP space is a limited resource. Amazon EC2 is adopting NAT to ensure that we are able to efficiently make use of our public Internet addresses.

Furthermore, the new NAT networking will enable Amazon to deliver new features in the future. For example, some users might not want external addresses. This would allow for non-Internet routable clusters, which will further preserve IPs and increase security for those not running public facing servers.

Can I use a static IP in my instances?

Not at present. Your image must be configured as a DHCP client and it will be assigned an IP address. Currently, all instances come with Internet- addressable IP addresses. If you enable access through the firewall from the "world", you can address them from anywhere.

How does the instance know its public and private addresses?

From within the instance, issue the following HTTP queries:

To obtain the internal IP address:

curl http://169.254.169.254/2009-08-15//meta-data/local-ipv4

To obtain the public IP address:

curl http://169.254.169.254/2009-08-15//meta-data/public-ipv4

Why am I limited to 5 elastic IP addresses?

Public (IPV4) Internet addresses are a scarce public resource. Amazon EC2 is committed to helping use that space efficiently.

By default, all accounts are limited to 5 elastic IP addresses. If you need more than 5 Elastic IP addresses, please complete the Amazon EC2 Elastic IP Address Request Form. We will ask you to think through your use case and help us understand your need for additional addresses.

Is my elastic IP addressed fixed to a single instance?

Unlike a traditional dedicated IP addresses, an elastic IP can be assigned to many different instances over time.

Is there a minimum usage required for elastic IP addresses?

When operating within the 5 address limit, you can leave addresses unattached as you need. However, we reserve the right to reclaim elastic IP addresses that are chronically underutilized.

Is there a charge for elastic IP addresses?

To ensure our customers are efficiently using elastic IP addresses, we impose the a small hourly charge when these IP addresses are not mapped to an instance. When these IP addresses are mapped to an instance, they are free of charge. To avoid charges for elastic IP addresses that you are not using, use ReleaseAddress.

Do I need one elastic IP address for every instance that I have running?

You do not need an elastic IP address for all your instances. By default, every instance comes with a private IP address and an Internet routable public IP address. These addresses are fixed for the life of the instance. We believe this should be adequate for many applications where you do not need a long lived Internet routable end point (e.g., compute clusters, web crawling, and backend services).

Why don't you use IPV6 addresses?

Because of the scarcity of IPV4 Internet address, Amazon EC2 will be actively investigating the use of IPV6 addresses. We believe this is the only tenable long term solution. We don't yet have a timeline for introducing IPV6 addresses, but when we do support IPV6 addresses, we will be able to remove the friction we have imposed with IPV4 address.

Can I launch an instance with no public IP address?

You cannot currently launch an instance without a public IP address. We understand that for many applications, it is desirable to have no Internet routable IP address (e.g., internal databases).

How long does it take to remap an elastic IP address?

After you successfully make an API call to remap an IP address, it will usually occur within a few minutes.

Will I be charged for the time when my IP address is unattached because my instance failed?

You are not charged until your elastic IP address has been unattached for a full hour. As long as you are monitoring your instances, you will have plenty of time to reattach your instance before the charge is metered.

Am I limited to 100 elastic IP remaps per month?

No. The first 100 remaps per account are free. After that, there will be a charge for each remap.