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AWS Resource Access Manager

1. Introduction​

In modern multi-account AWS environments, resource management can become complex and prone to inefficiencies. AWS Resource Access Manager addresses this challenge by allowing you to share critical AWS resources with other accounts within your organization or with external accounts. This capability is particularly important when designing scalable architectures where different teams or projects require access to common underlying infrastructure, such as networking components, without exposing the entirety of your resources.

2. What is AWS Resource Access Manager (RAM)?​

AWS Resource Access Manager is a service designed to simplify the process of sharing AWS resources among different accounts. At its core, AWS RAM enables the sharing of resources such as VPC subnets, Transit Gateways, Route53 Resolver Rules, and License Manager configurations, among others.

The service allows the resource owner to specify which AWS accounts or organizational units are permitted to use a shared resource. Importantly, while the shared resource—typically a networking component like a VPC subnet—is made available to multiple accounts, the actual resources deployed within that subnet (such as EC2 instances, Application Load Balancers, or RDS databases) remain under the sole control of the respective account owners. This segregation ensures that each account has autonomy over its resources, maintaining both operational independence and security.

3. Key Concepts and Benefits of Resource Sharing​

AWS RAM introduces several key concepts that underpin its functionality and benefits:

Resource Sharing Model​

  • Centralized Infrastructure, Decentralized Management: The service allows you to share the underlying infrastructure (e.g., VPC subnets) while keeping the deployed resources—such as compute instances, load balancers, and databases—isolated within each account.
  • Ownership and Control: Even though the networking layer is shared, each participating account is responsible for the resources it deploys. This means that one account cannot view, modify, or delete resources that belong to another, preserving operational boundaries and security.

Operational Efficiency​

  • Avoidance of Resource Duplication: By sharing common resources like VPC subnets, organizations can eliminate the need to replicate infrastructure across accounts. This consolidation reduces overhead, simplifies network management, and ensures consistent configurations.
  • Simplified Connectivity: Shared networking layers enable seamless communication between resources deployed in different accounts. For example, an EC2 instance in one account can communicate with an RDS database in the VPC owner’s account using private IP addresses, streamlining the architecture.

Improved Security​

  • Isolated Resource Management: The service’s design ensures that while the networking layer is shared, the resources within it are isolated. Each account’s resources remain private and secure, accessible only to the owning account.
  • Enhanced Communication Security: Using private IP addressing for inter-resource communication minimizes exposure to the public internet, thereby reducing the risk of unauthorized access.

4. Supported Resources and Limitations​

AWS RAM supports a variety of resource types, though the most common and exam-relevant resource is the VPC subnet. Understanding the scope of what can—and cannot—be shared is crucial for leveraging AWS RAM effectively.

Supported Resources​

  • VPC Subnets: The primary resource shared via AWS RAM, enabling multiple accounts to utilize a common networking segment while keeping their deployed resources separate.
  • AWS Transit Gateway: Facilitates connectivity across VPCs and on-premises networks by acting as a central hub.
  • Route53 Resolver Rules: Allows for the sharing of DNS resolution rules across accounts.
  • License Manager Configurations: Enables sharing of license configurations to manage software licenses centrally.
  • Additional Resources: Other resources that can be shared include Aurora DB Clusters, Capacity Reservations, CodeBuild Projects, Dedicated Hosts, Image Builder resources, Resolver Rules, Resource Groups, and Traffic Mirror Targets.

Limitations​

  • Exclusion of Certain Resources: Not all resources can be shared. For instance, security groups and the default VPC cannot be shared using AWS RAM.
  • Organizational Boundaries: In the case of VPC subnets, the shared subnet must be part of a non-default VPC and generally must reside within the same organization.
  • Acceptance Requirement: Once a resource share is created, the recipient accounts must explicitly accept the share before they can utilize the resource. This adds an additional layer of control to ensure that resources are shared only with intended parties.

These limitations ensure that AWS RAM remains a secure and manageable solution for resource sharing, requiring careful planning and configuration to maximize its benefits while minimizing potential risks.

5. Security Considerations in Resource Sharing​

Security is a paramount consideration in any multi-account AWS environment. AWS RAM’s design helps mitigate risks while providing robust mechanisms for secure resource sharing.

Isolation of Deployed Resources​

  • Controlled Visibility: Even though a common VPC subnet is shared among accounts, the actual resources deployed within that subnet (such as EC2 instances, ALBs, or RDS databases) are not visible to other accounts. This ensures that sensitive data and configurations remain isolated.
  • Independent Management: Each account retains complete control over its resources, meaning that modifications or deletions in one account do not impact the resources of another. This separation of responsibilities enhances overall security.

Secure Inter-Account Communication​

  • Private Networking: By enabling communication over private IP addresses, AWS RAM reduces the exposure of traffic to the public internet. This is particularly beneficial for applications that require secure, low-latency connectivity.
  • Security Group Integration: While the underlying shared networking layer is common, individual security groups can be configured to enforce strict access controls between resources across accounts. For example, you can allow an EC2 instance in one account to access an RDS database in another by adjusting the respective security group rules.

Access Control and Compliance​

  • Granular Permissions: AWS RAM allows you to specify exactly which accounts or organizational units have access to a shared resource. This granular control is essential for maintaining compliance with internal policies and regulatory requirements.
  • Auditability: By centralizing the sharing mechanism, AWS RAM simplifies the process of auditing resource access. You can track which resources are shared with which accounts, making it easier to monitor and manage compliance.

Overall, the security features of AWS RAM are designed to provide a robust framework that not only facilitates resource sharing but also safeguards each account's unique resources against unauthorized access or inadvertent modifications.

6. Conclusion​

In summary, AWS Resource Access Manager is a straightforward yet powerful service that addresses the challenges of resource sharing in complex AWS architectures. Its capabilities are particularly valuable for organizations looking to optimize resource utilization, enhance connectivity, and maintain stringent security standards across multiple accounts.