EC2 Elastic IPs
Table of Contents
Table of Contents
Overview
An Elastic IP (EIP) is an IP address that you can reserve from AWS for your account. Once you've created an Elastic IP, you can assign it to any instance of your choice. Once you reserve an Elastic IP, nobody else can use that IP address. Elastic IPs are unique because they are dynamically remappable IP addresses that make it easier to manage servers and make global changes in the cloud. Whereas static IPs are associated to a particular machine, EIPs can be reassigned to different instances when necessary as you launch and terminate servers. Typically, you will associate EIPs to your frontend servers. You can assign an EIP to a running instance or associate an EIP when an instance is launched. Be careful, you can also "steal" an EIP from one of your instances. As a best practice, you should age any new EIP before you assign it to one of your public facing servers because that IP address may still be temporarily cached and mapped to its previous instance. You do not want to accidentally inherit unintended traffic from its predecessor.
- Click the disassociate button to disassociate an Elastic IP from an instance. If you disassociate an EIP from a running instance, it will remain without a public IP address until Amazon re-assigns a new one, which can take several minutes.
- Click the delete button to permanently delete an Elastic IP from your account. When you delete an EIP, you are essentially releasing that IP address back to Amazon so that it can't be reissued to another account. Delete with caution because you will never be able to get that exact same IP address ever again. If you delete an EIP from a running instance, it will remain without a public IP address until Amazon re-assigns a new one, which can take several minutes. When you delete an EIP, it will not disappear from the GUI until Amazon has finished releasing the IP address.
- If an Elastic IP is locked, it cannot be deleted, associated, or disassociated. To lock an EIP, you must lock the server.
Note: By default, Amazon will allow you to reserve 5 EIPs per account. You can request more directly with Amazon. EIPs are free to use as long as they are being used (associated) by an operational instance. However, you will be charged by Amazon for unused EIPs. This is because they are publicly routable IP addresses. Public IPv4 addresses are a limited resource, so if you reserve addresses and do not use them, it is considered a wasteful practice and you will be charged by Amazon.
Action Buttons
- New - Create a new Elastic IP address. You should receive a flash status message in the RightScale banner/header portion of the Dashboard. For example: "New IP '174.129.241.232' was allocated successfully. New IPs may take several minutes to appear."
- New VPC EIP - Create a new Elastic IP address, but one that will only be designated for use by an instance in a VPC.
Actions
- Assign an Elastic IP at Launch
- Transfer an Elastic IP to a running instance
- Assign an Elastic IP to an Inactive Server
- Check to see if an instance is using an EIP
- Disassociate an Elastic IP from a running instance?
- Assign an Elastic IP after an instance is launched
- Create a New Elastic IP (EIP)
- Switch my frontends to use EIastic IPs
Concepts
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