Question 554 - SAP-C01 discussion

In AWS OpsWorks, you can control user access to a stack's instances by creating it in a virtual private cloud (VPC). For example, you might not want users to have direct access to your stack's app servers or databases and instead require that all public traffic be channeled through an Elastic Load Balancer. A VPC consists of one or more subnets, each of which contains one or more instances. Each subnet has an associated routing table that directs outbound traffic based on its destination IP address. Instances within a VPC can generally communicate with each other, regardless of their subnet. Subnets whose instances can communicate with the Internet are referred to as public subnets. Subnets whose instances can communicate only with other instances in the VPC and cannot communicate directly with the Internet are referred to as private subnets. AWS OpsWorks requires the VPC to be configured so that every instance in the stack, including instances in private subnets, has access to the following endpoints:

The AWS OpsWorks service, https://opsworks-instance-service.us-east-1.amazonaws.com.

Amazon S3

The package repositories for Amazon Linux or Ubuntu 12.04 LTS, depending on which operating system you specify. Your app and custom cookbook repositories.

Reference: http://docs.aws.amazon.com/opsworks/latest/userguide/workingstacks-vpc.html#workingstacks-vpc-basics