What is Elastic IP in AWS ?
AWS EC2 instances are computing services that can be used to host web services and applications. These instances belong to an Amazon virtual cloud and they can be accessed with the help of IPs in your specified range.
Amazon EC2 instances serves with two types of external IPs – Public IP and Elastic IP.
When a new EC2 instance is started, it will be automatically assigned a public IP to access that instance. This public IP address can be used to access the EC2 instance from outside. However this public IP changes on every subsequent EC2 reboot.  As a result, services in that instance that use DNS, can face downtime during this change in IP.  So to counter or eliminate this issue of downtime of DNS service, Elastic IP is introduced.  Elastic IPs (EIPs) are static IPs allocated to a specific AWS account. They are public IPv4 addresses, that can be manually assigned to EC2 instances to access them from outside. The elastic IPs are static in nature and does not change with an instance restart. Their static nature makes EIPs a more preferable option for services in EC2 instances.

Here are some benefits of using elastic IPs, which prompts us to prefer them over public IPs for our customers’ EC2 instances.

  1. Static and public – Being static in nature, we use the Elastic IPs for public services that require static IPs – such as web server, dns or email server.
  2. Flexibility – As Elastic IPs are allotted to each AWS account and are not specific to an EC2 instance, we allocate an Elastic IP to any EC2 instance as and when a requirement arise.
  3. Load balancing – When one EC2 instance fails or gets overloaded with traffic, we allocate its associated EIP to another EC2 instance, by configuring a failover setup in the system. This helps us to ensure uninterrupted service for the users.
  4. Fail-over setup – Having multiple Elastic IPs for an AWS account enables us to quickly map a service from one IP to another, in case of issues such as IP blacklisting or IP changes.
  5. Uptime – With our load balancing and fail-over setup with the help of elastic IPs, we are able to prevent downtime in services that can happen due to maintenance or DNS propagation.

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