A summary of the differences between Public vs Private  vs Elastic IP in a AWS environment.

Public IPs:

        1.  IP assigned to one Machine and is routable on the internet.

        2.  IP is unique and never duplicated at the same time.

        3.  Can easily be geographically located.

Private IPs

        1.  IP only identifiable on private network.

        2.  IPs unique on single private network but can be duplicated on another.

        3.  IP must go through internet gateway as a proxy to access internet.

        4.  IP is that can be used are specified in a range.

Elastic IPs

        1.  Stopping and Starting an EC2 Instance, public IP can change.

        2.  To get a stable IP for EC2 Instance, you have to request an Elastic IP

        3.  Elastic IP is a public IPv4 address you own until deleted.

        4.  Elastic IP can only be attached to single EC2 Instance at a time.

        5.  Elastic IP allow you to mask Instance failure with rapid remapping to another Instance.

EC2 Instances by default come with:

        1.  One Private IP Address for internal AWS network.

        2.  One Public IP for internet.

        3.  SSH must use the public IP because it is assumed you are on outside network.

        4.  Starting and Stopping can cause the Public IP to Change.

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