Public IP_ Private IP_ Elastic IP in AWS

Public IP

• In this IP, the machine can be recognized over the internet
• The IP must be unique IP (no two machines can have the same Public IP).
• It is used to communicate between the instance and the internet.
• When we launch an instance it automatically gets assigned with a public IP from the public address pool.

Private IP

• In this IP, the machine cannot be recognized over the internet, to connect over the internet we need an internet gateway.
• It is used within the organizations.
• The IP must be unique across the private network.
• But two different organizations can have the same private IP.
• It is used to communicate between the instances in the same VPC.

Elastic IP

• When we stop an EC2 instance and again start it the public IP gets changed.
• To fix this public IP issue, we use elastic IP.
• Elastic IP keeps an IP associate permanently to the instance public IP.
• We can associate only one instance to an elastic IP at a time.
• We can associate and di-associate the elastic IP.
• We can have only 5 Elastic IPs in an account.

Note: we can increase this by asking AWS to increase with a valid reason