What is the difference bettwen Elastic IP and Public IP? (52 of 285 technotes for 2015)

Elastic IP address - designed for dynamic cloud computing

• static IP address
• assigned to your account, until you release it.
  
• there is a small hourly charge for EIP which is not associated to and instance, or if it is associated to an instance, but the instance is turned down.
  
• EIP is limited to 5 per account
• IPv4 static IP’s are very scare, so the limitation
• EIP should be used only incase of Load Balancing and use DNS hostnames for all other internode communication
  
• You can mask the failure of an instance by rapidly re-mapping the address to another instance of the account.

Public IP Address -

• dynamically assigned IP Addresses
• also given an external dns hostname
• when launching an instance in VPC … public IP is determined by subnet setting
• when an instance is stopped – public ip address is released to the Amazon’s pool of public addresses
  
• public ip address is released when it is associated with EIP
  
• if an instance is assigned an EIP, it automatically received a DNS hostname, if DNS hostname is enabled.

Best Practice  EIP (Static IP)

• Internet IP Address is a scare public resource.
• Use EIP for Load Balancers use case.
  
• Use DNS hostnames for all internode communication.

References:

http://amzn.to/1aW1WCS