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Hurricane Development
Asked: 2016-05-03 12:03:16 +0800 CST

Why does an AWS EC2 instance need public and private DNS?

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I am creating my own VPC and was reading some documentation. AWS documentation for DNS with VPC (click here to view) says

To enable an EC2 instance to be publicly accessible, it must have a public IP address, a DNS hostname, and DNS resolution.

Is this true? Why?

Is a private IP address in combination with an elastic IP address not enough to access the instance publicly and privately?

domain-name-system amazon-ec2 amazon-web-services amazon-vpc

1 Answers

  1. Best Answer

    An Elastic IP address is a public IP address, so that takes care of public access.

    While you can access your instance from within AWS's network with the public ElasticIP address instead of using the private IP address, you'll pay for it:

    https://aws.amazon.com/ec2/pricing/

    Data Transfer IN To Amazon EC2 From

    • Amazon EC2, Amazon RDS, Amazon Redshift and Amazon ElastiCache instances or Elastic Network Interfaces in the same Availability Zone
      • Using a private IP address $0.00 per GB
      • Using a public or Elastic IP address $0.01 per GB

    Data Transfer OUT From Amazon EC2 To

    • Amazon EC2, Amazon RDS, Amazon Redshift or Amazon ElastiCache instances, Amazon Elastic Load Balancing, or Elastic Network Interfaces in the same Availability Zone
      • Using a private IP address $0.00 per GB
      • Using a public or Elastic IP address $0.01 per GB

    You don't need DNS to access the instance -- the IP alone is sufficient.

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