AWS Certified Advanced Networking – Specialty (ANS-C01)Network DesignMedium
A global company has a complex network architecture with hundreds of VPCs spread across multiple AWS accounts and regions. They need to implement a new IP addressing scheme to prevent CIDR block overlaps and simplify routing. The new scheme must allow for future growth and be easily auditable. Which IP addressing strategy is most suitable for this scenario?
- ARelying on AWS default VPC CIDR blocks and dynamic routing protocols.
- BImplementing a hierarchical IP addressing scheme with a central IP address management (IPAM) tool.
- CUsing public IP address ranges (e.g., 1.0.0.0/8) and Network Address Translation (NAT).
- DAssigning random private IP address ranges (e.g., 10.0.0.0/16, 172.16.0.0/16) to each VPC.
Show answer & explanationAnswer & explanation
Correct answer: B. Implementing a hierarchical IP addressing scheme with a central IP address management (IPAM) tool.
A hierarchical IP addressing scheme systematically allocates CIDR blocks, preventing overlaps and simplifying routing. A central IPAM tool (like AWS IPAM) automates this process, ensuring auditability and managing IP space efficiently across a large, complex environment, accommodating future growth.
Why the other options are wrong
- A. AWS default VPC CIDR blocks are limited and often overlap. Dynamic routing helps but doesn't solve the fundamental issue of overlapping IP spaces or provide a structured allocation strategy.
- C. Using public IP addresses for internal VPCs is a security risk and inefficient, requiring NAT for private communication.
- D. Assigning random private IP ranges quickly leads to overlaps in large environments, making routing complex or impossible.
Hierarchical IPAM
A structured approach to IP address allocation, typically managed by an IPAM tool, that assigns CIDR blocks in a hierarchical manner to prevent overlaps and simplify network management in large, multi-VPC, multi-account environments.
- Prevents IP address overlaps across VPCs and on-premises networks.
- Simplifies routing tables by enabling route summarization.
- Provides a clear structure for IP space consumption and auditing.
- AWS IPAM is a native service that helps implement this strategy.
Memory trick: Hierarchical IPAM is the organized map for your network's address space.